Patent Application
20100255475
The invention relates to generally methods of identifying subject who have a genetic predisposition for developing osteoporosis or osteoporosis-related conditions or diseases.
In 1993, osteoporosis was identified as “one of the leading diseases of women” by Bernadine Healy, MD, then director of the National Institutes of Health. Complications following osteoporosis fractures are the fourth leading cause of death for women over the age of 65, following heart disease, cancer and stroke. It is the leading cause of disability in the United States and the most common cause of hip fracture.
Twenty-five million Americans suffer from osteoporosis, of which 85% are women. Type 1 osteoporosis, which is postmenopausal osteoporosis stemming from loss of estrogen, affects more than half of all women over 65 and has been detected in as many as 90 percent of women over age 75. Type II or senile osteoporosis which is strictly age related, affects both men and women usually over the age of seventy. Type III, the newest classification affecting both sexes, is drug-induced, for example, by long-term steroid therapy, known to accelerate bone loss. Patient groups that receive long term steroid therapy include asthmatics (7 million over the age of 18 in the United States) as well as patients with rheumatoid arthritis or other autoimmune diseases. Type IV is caused by an underlying disease such as rheumatoid arthritis (prevalence of 1-2% in the population).
Osteoporosis is responsible for a majority of the 1.5 million bone fractures each year leading to disabilities costing 10 billion dollars in medical, social and nursing-home costs. Even under the best care 40% of patients 65 years of age or older will not survive two years following a hip fracture.
In 1991, one in three American women were 50 years or older. The baby boom generation will begin to enter this age group in 1996. Because the average woman lives some thirty years after menopause, with present trends, osteoporosis threatens to be one of the biggest health threats of modern times.
Lifestyle can be a factor in onset of osteoporosis and in particular can be an important factor in building and maintaining healthy bone mass to prevent osteoporosis. Currently, persons under 65 are more likely than their parents to have had a sedentary lifestyle, bad eating habits, increased alcohol and caffeine intake, and a history of greater medication associated with bone loss. It is also clear that there is a genetic predisposition to the development of osteoporosis (see WO 94/03633 for a discussion of genetic factors in osteoporosis, which is herein incorporated by reference).
It would therefore be useful to be able to identify early those individuals at greatest risk for developing osteoporosis so that the individual can be counseled to make appropriate life style changes or institute other therapeutic interventions. For example, calcium supplements and exercise have been shown to be valuable preventive factors if used during a critical early age window. Hormone replacement therapy (HRT) has also been used successfully to combat osteoporosis occurring after menopause. HRT may be of greatest benefit if used early in the disease process before major bone loss has occurred. Since HRT has potentially serious side-effects, it would be useful for women to know their personal risk level for osteoporosis when making decisions about the use of HRT versus other interventions aimed at reducing the risk of developing osteoporosis.
The following published patent applications describe a variety of methods for diagnosing, monitoring and/or treating osteoporosis: WO 94/20615, WO 95/01995, WO 94/14844, EP93113604, WO/8809457, WO93/11149 and WO/9403633. The following references describe the association of various IL-1 gene polymorphisms in osteoporosis: U.S. Pat. No. 5,698,399; Eastell, R. et al., (1998) Bone 23 (5S): S375; Eastell, R. et al. and Keen, R W et al., (1998) Bone 23: 367-371.
Genetics of the IL-1 Gene Cluster
The IL-1 gene cluster is on the long arm of chromosome 2 (2q13) and contains at least the genes for IL-1α (IL-1A), IL-1β (IL-1B), and the IL-1 receptor antagonist (IL-1RN), within a region of 430 Kb (Nicklin, et al. (1994) Genomics, 19: 382-4). The agonist molecules, IL-1α and IL-1β, have potent pro-inflammatory activity and are at the head of many inflammatory cascades. Their actions, often via the induction of other cytokines such as IL-6 and IL-8, lead to activation and recruitment of leukocytes into damaged tissue, local production of vasoactive agents, fever response in the brain and hepatic acute phase response. All three IL-1 molecules bind to type I and to type II IL-1 receptors, but only the type I receptor transduces a signal to the interior of the cell. In contrast, the type II receptor is shed from the cell membrane and acts as a decoy receptor. The receptor antagonist and the type II receptor, therefore, are both anti-inflammatory in their actions.
Inappropriate production of IL-1 plays a central role in the pathology of many autoimmune and inflammatory diseases, including rheumatoid arthritis, inflammatory bowel disorder, psoriasis, and the like. In addition, there are stable inter-individual differences in the rates of production of IL-1, and some of this variation may be accounted for by genetic differences at IL-1 gene loci. Thus, the IL-1 genes are reasonable candidates for determining part of the genetic susceptibility to inflammatory diseases, most of which have a multifactorial etiology with a polygenic component.
Certain alleles from the IL-1 gene cluster are known to be associated with particular disease states. For example, IL-1RN (VNTR) allele 2 (U.S. Pat. No. 5,698,399) and IL-1RN (VNTR) allele 1 (Keen R W et al., (1998) Bone 23:367-371) have been reported to be associated with osteoporosis. Further IL-1RN (VNTR) allele 2 has been reported to be associated with nephropathy in diabetes mellitus (Blakemore, et al. (1996) Hum. Genet. 97(3): 369-74), alopecia areata (Cork, et al., (1995) J. Invest. Dermatol. 104(5 Supp.): 15S-16S; Cork et al. (1996) Dermatol Clin 14: 671-8), Graves disease (Blakemore, et al. (1995) J. Clin. Endocrinol. 80(1): 111-5), systemic lupus erythematosus (Blakemore, et al. (1994) Arthritis Rheum. 37: 1380-85), lichen sclerosis (Clay, et al. (1994) Hum. Genet. 94: 407-10), and ulcerative colitis (Mansfield, et al. (1994) Gastroenterol. 106(3): 637-42)).
In addition, the IL-1A allele 2 from marker −889 and IL-1B (TaqI) allele 2 from marker +3954 have been found to be associated with periodontal disease (U.S. Pat. No. 5,686,246; Kornman and diGiovine (1998) Ann Periodont 3: 327-38; Hart and Kornman (1997) Periodontol 2000 14: 202-15; Newman (1997) Compend Contin Educ Dent 18: 881-4; Kornman et al. (1997) J. Clin Periodontol 24: 72-77). The IL-1A allele 2 from marker −889 has also been found to be associated with juvenile chronic arthritis, particularly chronic iridocyclitis (McDowell, et al. (1995) Arthritis Rheum. 38: 221-28). The IL-1B (TaqI) allele 2 from marker +3954 of IL-1B has also been found to be associated with psoriasis and insulin dependent diabetes in DR3/4 patients (di Giovine, et al. (1995) Cytokine 7: 606; Pociot, et al. (1992) Eur J. Clin. Invest. 22: 396-402). Additionally, the IL-1RN (VNTR) allele 1 has been found to be associated with diabetic retinopathy (see U.S. Ser. No. 09/037,472, and PCT/GB97/02790). Furthermore allele 2 of IL-1RN (VNTR) has been found to be associated with ulcerative colitis in Caucasian populations from North America and Europe (Mansfield, J. et al., (1994) Gastroenterology 106: 637-42). Interestingly, this association is particularly strong within populations of ethnically related Ashkenazi Jews (PCT WO97/25445).
Genotype Screening
Traditional methods for the screening of heritable diseases have depended on either the identification of abnormal gene products (e.g., sickle cell anemia) or an abnormal phenotype (e.g., mental retardation). These methods are of limited utility for heritable diseases with late onset and no easily identifiable phenotypes such as, for example, vascular disease. With the development of simple and inexpensive genetic screening methodology, it is now possible to identify polymorphisms that indicate a propensity to develop disease, even when the disease is of polygenic origin. The number of diseases that can be screened by molecular biological methods continues to grow with increased understanding of the genetic basis of multifactorial disorders.
Genetic screening (also called genotyping or molecular screening), can be broadly defined as testing to determine if a patient has mutations (alleles or polymorphisms) that either cause a disease state or are “linked” to the mutation causing a disease state. Linkage refers to the phenomenon th DNA sequences which are close together in the genome have a tendency to be inherited together. Two sequences may be linked because of some selective advantage of co-inheritance. More typically, however, two polymorphic sequences are co-inherited because of the relative infrequency with which meiotic recombination events occur within the region between the two polymorphisms. The co-inherited polymorphic alleles are said to be in linkage disequilibrium with one another because, in a given human population, they tend to either both occur together or else not occur at all in any particular member of the population. Indeed, where multiple polymorphisms in a given chromosomal region are found to be in linkage disequilibrium with one another, they define a quasi-stable genetic “haplotype.” In contrast, recombination events occurring between two polymorphic loci cause them to become separated onto distinct homologous chromosomes. If meiotic recombination between two physically linked polymorphisms occurs frequently enough, the two polymorphisms will appear to segregate independently and are said to be in linkage equilibrium.
While the frequency of meiotic recombination between two markers is generally proportional to the physical distance between them on the chromosome, the occurrence of “hot spots” as well as regions of repressed chromosomal recombination can result in discrepancies between the physical and recombinational distance between two markers. Thus, in certain chromosomal regions, multiple polymorphic loci spanning a broad chromosomal domain may be in linkage disequilibrium with one another, and thereby define a broad-spanning genetic haplotype. Furthermore, where a disease-causing mutation is found within or in linkage with this haplotype, one or more polymorphic alleles of the haplotype can be used as a diagnostic or prognostic indicator of the likelihood of developing the disease. This association between otherwise benign polymorphisms and a disease-causing polymorphism occurs if the disease mutation arose in the recent past, so that sufficient time has not elapsed for equilibrium to be achieved through recombination events. Therefore identification of a human haplotype which spans or is linked to a disease-causing mutational change, serves as a predictive measure of an individual's likelihood of having inherited that disease-causing mutation. Importantly, such prognostic or diagnostic procedures can be utilized without necessitating the identification and isolation of the actual disease-causing lesion. This is significant because the precise determination of the molecular defect involved in a disease process can be difficult and laborious, especially in the case of multifactorial diseases such as inflammatory disorders.
Indeed, the statistical correlation between an inflammatory disorder and an IL-1 polymorphism does not necessarily indicate that the polymorphism directly causes the disorder. Rather the correlated polymorphism may be a benign allelic variant which is linked to (i.e. in linkage disequilibrium with) a disorder-causing mutation which has occurred in the recent human evolutionary past, so that sufficient time has not elapsed for equilibrium to be achieved through recombination events in the intervening chromosomal segment. Thus, for the purposes of diagnostic and prognostic assays for a particular disease, detection of a polymorphic allele associated with that disease can be utilized without consideration of whether the polymorphism is directly involved in the etiology of the disease. Furthermore, where a given benign polymorphic locus is in linkage disequilibrium with an apparent disease-causing polymorphic locus, still other polymorphic loci which are in linkage disequilibrium with the benign polymorphic locus are also likely to be in linkage disequilibrium with the disease-causing polymorphic locus. Thus these other polymorphic loci will also be prognostic or diagnostic of the likelihood of having inherited the disease-causing polymorphic locus. Indeed, a broad-spanning human haplotype (describing the typical pattern of co-inheritance of alleles of a set of linked polymorphic markers) can be targeted for diagnostic purposes once an association has been drawn between a particular disease or condition and a corresponding human haplotype. Thus, the determination of an individual's likelihood for developing a particular disease of condition can be made by characterizing one or more disease-associated polymorphic alleles (or even one or more disease-associated haplotypes) without necessarily determining or characterizing the causative genetic variation.
The invention provides a genetic predisposition test that identifies subjects that have an elevated risk for developing osteoporosis or osteoporosis-related conditions or diseases. In particular, the invention provides a genetic predisposition test that identifies women at elevated risk for developing osteoporosis-related vertebral fracture during menopause.
In one aspect, the presence, absence or predisposition to developing osteoporosis in a subject is determined by detecting in the subject an osteoporosis-associated genotype. The presence of the genotype indicates that the subject has or is predisposed to developing osteoporosis. In contrast, absence of the genotype indicates that the subject does not have or is not predisposed to developing osteoporosis. A symptom of osteoporosis is alleviated or the development of osteoporosis is presented in a subject by detecting the presence of an osteoporosis-associated genetotype and administering to the subject a therapeutic that compensates for the osteoporosis. Symptoms of osteoporosis include for example, loss of height as a result of weakened spines, cramps in the legs at night, bone pain and tenderness, Neck pain, discomfort in the neck other than from injury or trauma, persistent pain in the spine or muscles of the lower back, abdominal pain, tooth loss, rib pain, broken bones, spinal deformities become evident like stooped posture, an outward curve at the top of the spine as a result of developing a vertebral collapse on the back, fatigue, periodontal disease or brittle fingernails. Osteoporosis is determined by methods known in the art, such as by bone mineral density. For example Bone mineral density (BMD) in a particular patient is compared with those of a 25 year old female. BMD values which fall well below the average for the 25 year old female (stated statistically as 2.5 standard deviations below the average) are diagnosed as “osteoporotic”. If a patient has a BMD value less than the normal 25 year old female, but not 2.5 standard deviations below the average, the bone is said to be “osteopenic” (osteopenic means decreased bone mineral density, but not as sever as osteoporosis.
An osteoporosis associated genotype is for example, (a) genotype 2.2 at IL-1A (+4845), genotype 1.1 at IL-1B (−511), and genotype 1.1 at IL-1RN (+2018); (b) genotype 2.2 at IL-1B (−511), and genotype 2.2 at IL-1RN (+2018); or (c) genotype 2.2 at IL-1B (−511), and genotype 1.2 at IL-1RN (+2018)
In another aspect, the presence or absence of osteoporosis or a predisposition to developing osteoporosis in a subject is determined by detecting in the subject an osteoporosis associated allele. The presence of the allele indicates that the subject has or is predisposed to developing osteoporosis. In contrast, absence of the allele indicates that the subject does not have or is not predisposed to developing osteoporosis. An osteoporosis-associated allele is for example, an IL-1RN (+2018) allele, IL-1A (+4845) allele, and an IL-1B (−511). One, two, three or more alleles are detected. For example an IL-1B (−511) and an IL-1RN (+2018) are detected. Alternatively, an IL-1A (+4845) allele, and an IL-1RN (+2018) are detected. The subject is homozygous for the allele. Alternatively, the subject is heterozygous for the allele. The subject is a female. The subject is over 60 years of age. For example, the subject is between 65-90 years of age. The subject has not used hormone replacement therapy.
The osteoporosis associated genotype or allele is detected by methods known in the art. For example the genotype or allele is detected by allele specific oligonucleotide hybridization, size analysis, sequencing, hybridization, 5′ nuclease digestion, single-stranded conformation polymorphism, allele specific hybridization, primer specific extension or oligonucleotide ligation assay. Optionally, prior to or in conjunction with detection, the nucleic acid sample is subject to an amplification step.
Also included in the invention are kits for determining the existence, absence or a susceptibility to developing osteoporosis. The kits contain first primer oligonucleotide that hybridizes 5′ or 3′ to an IL-1A (+4845) allele, an IL-1B (−511) allele or an IL-1RN (+2018) allele. The oligonucleotide is 1000, 500, 250, 150, 100, 50, 25, 15, 10 or less nucleotides in length. Optionally, the kit contains a second primer oligonucleotide that hybridizes either 3′ or 5′ respectively to the allele allowing the allele to be amplified. In various aspects, the kits contain a detection means, an amplification means or a control.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.
The invention bases upon the discovery of a genotype associated with increased risk of developing osteoporosis or osteoporosis-related conditions or diseases such as vertebral fracture. Accordingly, the invention provides a genetic predisposition test that identifies women at elevated risk for developing osteoporosis-related vertebral fracture during or after menopause.
A genetic analysis is conducted herein on the association of increased vertebral deformity correlated to the occurrence of gene polymorphisms, including, inter alia, certain alleles of the Interleukin-1A (IL-1A), Interleukin-1B (IL-1B), and Interleukin-1RN (IL-1RN) genes, as well as alleles of vitamin D receptor (VDR), collagen 1A1 (COL1A1), estrogen receptor (ER), and parathyroid hormone receptor (PTHR) genes. Investigation of genetic influences on the development of fracture and rate of decline of bone mineral density by investigating gene polymorphisms in post-menopausal women is useful in assessing the clinical utility of employing genetic tests for identifying individuals at high risk in order to target preventative therapies.
One objective of this study is to determine whether specific variations in a variety of genes may be used to predict the risk of a woman experiencing a vertebral fracture after menopause. One specific gene family studied is the IL-1 gene family. The rationale for the involvement of IL-1 genes in bone metabolism and post-menopausal fracture risk is summarized below. Postmenopausal osteoporosis is characterized by a progressive loss of bone tissue that begins after menopause and may lead to fractures within 15-20 years from the time of onset of menopause (2-4). Although other contributing factors, such as skeletal development “peak bone mass”, age-related bone loss and bone quality are also important determinants of risk for subsequent fracture, a hormone-dependent increase in bone resorption and accelerated loss of bone mass in the first 5 to 10 years after menopause appears to be the most important pathogenetic factor (2-4).
There is evidence indicating that estrogen prevents bone loss by blocking the production of proinflammatory cytokines by bone marrow and bone cells (3). Numerous reports have demonstrated that natural or surgical menopause increases blood, bone marrow, and monocytic levels of IL-1 and TNF (2,3). In vitro studies have also demonstrated the ability of estrogen to suppress the production of these cytokines. The main consequence of increased cytokine production in the bone microenvironment is an expansion of the osteoclastic pool due to increased osteoclastogenesis and lengthening of osteoclast life span (3). In addition, enhanced cytokine production results in increased activity of mature osteoclasts. IL-1 and TNFα are also well-recognized inhibitors of bone formation (2). Moreover, IL-1 and TNFα are potent inducers of other cytokines, such as IL-6, M-CSF, and GM-CSF that regulate the differentiation of osteoclast precursor cells into mature osteoclasts (3). Therefore, with respect to osteoclastogenesis, IL-1 and TNFα should be regarded as “upstream” cytokines necessary for inducing the secretion of “downstream factors” that stimulate hematopoietic osteoclast precursors. This cascade mechanism ensures that small changes in IL-1 and TNFα levels results in large changes in osteoclast production.
A specific endogenous competitive inhibitor of IL-1, known as IL-1 receptor antagonist (IL-1ra), which has a 26% amino acid sequence homology with IL-1β, binds to cells expressing the IL-1 receptor with nearly the same affinity as the IL-1β but entirely without IL-1 agonist activity (5).
Examples of specific biological evidence of IL-1 induction of osteoclastogenesis and osteoclast activity comes from reports of mice insensitive to IL-1 due to the absence of expression of type I IL-1 receptor (6). These mice are protected against the bone loss induced by ovariectomy, thus demonstrating that IL-1 action through the IL-1 receptor is an essential mediator of the effects of estrogen deficiency in bone (6). A critical finding of this study is that the lack of IL-1 receptor does not alter bone mass in sham-operated mice, thus demonstrating that IL-1 is not essential for maintaining normal bone remodeling in estrogen replete mice (6). In a related study, Kimbell et al. (7) reported that the infusion of IL-1ra which blocks the functional activity of IL-1 and IL-1β had the same bone sparing effect of estrogen.
Extensive biological evidence for the involvement of IL-1, IL-1β and IL-1ra in bone metabolism supports the hypothesis that there are one or more single nucleotide polymorphisms (SNPs) within the IL-1 gene cluster that cause an alteration in the expression of these genes. Increased transcription or translation of the IL-1A and IL-1B genes or a decreased transcription or translation of the IL-1RN gene or even a slightly altered cytokine (IL-1, IL-1β or IL-1ra) due to a single amino acid substitution caused by a SNP within the coding region of the genes could impair the delicate balance of cytokines needed for normal bone turnover. Overproduction of IL-1 and/or IL-1β or the underproduction of IL-1ra could lead to an activated bone resorptive system in certain individuals who are carriers of these alternate alleles. The negative effect of these alleles of the IL-1 genes would be particularly apparent after menopause due to the removal of the inhibitory effect of estrogen on IL-1 gene expression.
For convenience, the meaning of certain terms and phrases employed in the specification, examples, and appended claims is provided below.
The term “allele” refers to the different sequence variants found at different polymorphic regions. For example, IL-1RN (VNTR) has at least five different alleles. The sequence variants may be single or multiple base changes, including without limitation insertions, deletions, or substitutions, or may be a variable number of sequence repeats.
The term “allelic pattern” refers to the identity of an allele or alleles at one or more polymorphic regions. For example, an allelic pattern may consist of a single allele at a polymorphic site, as for IL-1RN (VNTR) allele 1, which is an allelic pattern having at least one copy of IL-1RN allele 1 at the VNTR of the IL-1RN gene loci. Alternatively, an allelic pattern may consist of either a homozygous or heterozygous state at a single polymorphic site. For example, IL1-RN (VNTR) allele 2,2 is an allelic pattern in which there are two copies of the second allele at the VNTR marker of IL-1RN that corresponds to the homozygous IL-RN (VNTR) allele 2 state. Alternatively, an allelic pattern may consist of the identity of alleles at more than one polymorphic site.
The term “antibody” as used herein is intended to refer to a binding agent including a whole antibody or a binding fragment thereof which is specifically reactive with an IL-1 polypeptide. Antibodies can be fragmented using conventional techniques and the fragments screened for utility in the same manner as described above for whole antibodies. For example, F(ab)2 fragments can be generated by treating an antibody with pepsin. The resulting F(ab)2 fragment can be treated to reduce disulfide bridges to produce Fab fragments. The antibody of the present invention is further intended to include bispecific, single-chain, and chimeric and humanized molecules having affinity for an IL-1B polypeptide conferred by at least one CDR region of the antibody.
“Biological activity” or “bioactivity” or “activity” or “biological function”, which are used interchangeably, for the purposes herein means an effector or antigenic function that is directly or indirectly performed by an IL-1 polypeptide (whether in its native or denatured conformation), or by any subsequence thereof. Biological activities include binding to a target peptide, e.g., an IL-1 receptor. An IL-1 bioactivity can be modulated by directly affecting an IL-1 polypeptide. Alternatively, an IL-1 bioactivity can be modulated by modulating the level of an IL-1 polypeptide, such as by modulating expression of an IL-1 gene.
As used herein the term “bioactive fragment of an IL-1 polypeptide” refers to a fragment of a full-length IL-1 polypeptide, wherein the fragment specifically mimics or antagonizes the activity of a wild-type IL-1 polypeptide. The bioactive fragment preferably is a fragment capable of interacting with an interleukin receptor.
The term “an aberrant activity”, as applied to an activity of a polypeptide such as IL-1, refers to an activity which differs from the activity of the wild-type or native polypeptide or which differs from the activity of the polypeptide in a healthy subject. An activity of a polypeptide can be aberrant because it is stronger than the activity of its native counterpart. Alternatively, an activity can be aberrant because it is weaker or absent relative to the activity of its native counterpart. An aberrant activity can also be a change in an activity. For example an aberrant polypeptide can interact with a different target peptide. A cell can have an aberrant IL-1 activity due to overexpression or underexpression of an IL-1 locus gene encoding an IL-1 locus polypeptide.
“Cells”, “host cells” or “recombinant host cells” are terms used interchangeably herein to refer not only to the particular subject cell, but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact be identical to the parent cell, but are still included within the scope of the term as used herein.
A “chimera,” “mosaic,” “chimeric mammal” and the like, refers to a transgenic mammal with a knock-out or knock-in construct in at least some of its genome-containing cells.
The terms “control” or “control sample” refer to any sample appropriate to the detection technique employed. The control sample may contain the products of the allele detection technique employed or the material to be tested. Further, the controls may be positive or negative controls. By way of example, where the allele detection technique is PCR amplification, followed by size fractionation, the control sample may comprise DNA fragments of an appropriate size. Likewise, where the allele detection technique involves detection of a mutated protein, the control sample may comprise a sample of a mutant protein. However, it is preferred that the control sample comprises the material to be tested. For example, the controls may be a sample of genomic DNA or a cloned portion of the IL-1 gene cluster. However, where the sample to be tested is genomic DNA, the control sample is preferably a highly purified sample of genomic DNA.
The phrases “disruption of the gene” and “targeted disruption” or any similar phrase refers to the site specific interruption of a native DNA sequence so as to prevent expression of that gene in the cell as compared to the wild-type copy of the gene. The interruption may be caused by deletions, insertions or modifications to the gene, or any combination thereof.
The term “haplotype” as used herein is intended to refer to a set of alleles that are inherited together as a group (are in linkage disequilibrium) at statistically significant levels (pcorr<0.05). As used herein, the phrase “an IL-1 haplotype” refers to a haplotype in the IL-1 loci. An IL-1 inflammatory or proinflammatory haplotype refers to a haplotype that is indicative of increased agonist and/or decreased antagonist activities.
The terms “IL-1 gene cluster” and “IL-1 loci” as used herein include all the nucleic acid at or near the 2q13 region of chromosome 2, including at least the IL-1A, IL-1B and IL-1RN genes and any other linked sequences. (Nicklin et al., Genomics 19: 382-84, 1994). The terms “IL-1A”, “IL-1B”, and “IL-1RN” as used herein refer to the genes coding for IL-1, IL-1, and IL-1 receptor antagonist, respectively. The gene accession number for IL-1A, IL-1B, and IL-1RN are X03833, X04500, and X64532, respectively.
“IL-1 functional mutation” refers to a mutation within the IL-1 gene cluster that results in an altered phenotype (i.e. effects the function of an IL-1 gene or protein). Examples include: IL-1A (+4845) allele 2, IL-1B (+3954) allele 2, IL-1B (+6912) allele 2 and IL-1RN (+2018) allele 2.
“IL-1X (Z) allele Y” refers to a particular allelic form, designated Y, occurring at an IL-1 locus polymorphic site in gene X, wherein X is IL-1A, B, or RN and positioned at or near nucleotide Z, wherein nucleotide Z is numbered relative to the major transcriptional start site, which is nucleotide +1, of the particular IL-1 gene X. As further used herein, the term “IL-1X allele (Z)” refers to all alleles of an IL-1 polymorphic site in gene X positioned at or near nucleotide Z. For example, the term “IL-1RN (+2018) allele” refers to alternative forms of the IL-1RN gene at marker +2018. “IL-1RN (+2018) allele 1” refers to a form of the IL-1RN gene which contains a thymine (T) at position +2018 of the sense strand. Clay et al., Hum. Genet. 97:723-26, 1996. “IL-1RN (+2018) allele 2” refers to a form of the IL-1RN gene which contains a cytosine (C) at position +2018 of the plus strand. When a subject has two identical IL-1RN alleles, the subject is said to be homozygous, or to have the homozygous state. When a subject has two different IL-1RN alleles, the subject is said to be heterozygous, or to have the heterozygous state. The term “IL-1RN (+2018) allele 2,2” refers to the homozygous IL-1RN (+2018) allele 2 state. Conversely, the term “IL-1RN (+2018) allele 1,1” refers to the homozygous IL-1RN (+2018) allele 1 state. The term “IL-1RN (+2018) allele 1,2” refers to the heterozygous allele 1 and 2 state.
“IL-1 related” as used herein is meant to include all genes related to the human IL-1 locus genes on human chromosome 2 (2q 12-14). These include IL-1 genes of the human IL-1 gene cluster located at chromosome 2 (2q 13-14) which include: the IL-1A gene which encodes interleukin-1α, the IL-1B gene which encodes interleukin-1β, and the IL-1RN (or IL-1ra) gene which encodes the interleukin-1 receptor antagonist. Furthermore these IL-1 related genes include the type I and type II human IL-1 receptor genes located on human chromosome 2 (2q12) and their mouse homologs located on mouse chromosome 1 at position 19.5 cM. Interleukin-1α, interleukin-1β, and interleukin-1RN are related in so much as they all bind to IL-1 type I receptors, however only interleukin-1α and interleukin-1⊕ are agonist ligands which activate IL-1 type I receptors, while interleukin-1RN is a naturally occurring antagonist ligand. Where the term “IL-1” is used in reference to a gene product or polypeptide, it is meant to refer to all gene products encoded by the interleukin-1 locus on human chromosome 2 (2q 12-14) and their corresponding homologs from other species or functional variants thereof. The term IL-1 thus includes secreted polypeptides which promote an inflammatory response, such as IL-1α and IL-1β, as well as a secreted polypeptide which antagonize inflammatory responses, such as IL-1 receptor antagonist and the IL-1 type II (decoy) receptor.
An “IL-1 receptor” or “IL-1R” refers to various cell membrane bound protein receptors capable of binding to and/or transducing a signal from an IL-1 locus-encoded ligand. The term applies to any of the proteins which are capable of binding interleukin-1 (IL-1) molecules and, in their native configuration as mammalian plasma membrane proteins, presumably play a role in transducing the signal provided by IL-1 to a cell. As used herein, the term includes analogs of native proteins with IL-1-binding or signal transducing activity. Examples include the human and murine IL-1 receptors described in U.S. Pat. No. 4,968,607. The term “IL-1 nucleic acid” refers to a nucleic acid encoding an IL-1 protein.
An “IL-1 polypeptide” and “IL-1 protein” are intended to encompass polypeptides comprising the amino acid sequence encoded by the IL-1 genomic DNA sequences shown in
“Increased risk” refers to a statistically higher frequency of occurrence of the disease or condition in an individual carrying a particular polymorphic allele in comparison to the frequency of occurrence of the disease or condition in a member of a population that does not carry the particular polymorphic allele.
The term “interact” as used herein is meant to include detectable relationships or associations (e.g. biochemical interactions) between molecules, such as interactions between protein-protein, protein-nucleic acid, nucleic acid-nucleic acid and protein-small molecule or nucleic acid-small molecule in nature.
The term “isolated” as used herein with respect to nucleic acids, such as DNA or RNA, refers to molecules separated from other DNAs, or RNAs, respectively, that are present in the natural source of the macromolecule. For example, an isolated nucleic acid encoding one of the subject IL-1 polypeptides preferably includes no more than 10 kilobases (kb) of nucleic acid sequence which naturally immediately flanks the IL-1 gene in genomic DNA, more preferably no more than 5 kb of such naturally occurring flanking sequences, and most preferably less than 1.5 kb of such naturally occurring flanking sequence. The term isolated as used herein also refers to a nucleic acid or peptide that is substantially free of cellular material, viral material, or culture medium when produced by recombinant DNA techniques, or chemical precursors or other chemicals when chemically synthesized. Moreover, an “isolated nucleic acid” is meant to include nucleic acid fragments which are not naturally occurring as fragments and would not be found in the natural state. The term “isolated” is also used herein to refer to polypeptides which are isolated from other cellular proteins and is meant to encompass both purified and recombinant polypeptides.
A “knock-in” transgenic animal refers to an animal that has had a modified gene introduced into its genome and the modified gene can be of exogenous or endogenous origin.
A “knock-out” transgenic animal refers to an animal in which there is partial or complete suppression of the expression of an endogenous gene (e.g, based on deletion of at least a portion of the gene, replacement of at least a portion of the gene with a second sequence, introduction of stop codons, the mutation of bases encoding critical amino acids, or the removal of an intron junction, etc.).
A “knock-out construct” refers to a nucleic acid sequence that can be used to decrease or suppress expression of a protein encoded by endogenous DNA sequences in a cell. In a simple example, the knock-out construct is comprised of a gene, such as the IL-1RN gene, with a deletion in a critical portion of the gene, so that active protein cannot be expressed therefrom. Alternatively, a number of termination codons can be added to the native gene to cause early termination of the protein or an intron junction can be inactivated. In a typical knock-out construct, some portion of the gene is replaced with a selectable marker (such as the neo gene) so that the gene can be represented as follows: IL-1RN 5′/neo/IL-1RN 3′, where IL-1RN 5′ and IL-1RN 3′, refer to genomic or cDNA sequences which are, respectively, upstream and downstream relative to a portion of the IL-1RN gene and where neo refers to a neomycin resistance gene. In another knock-out construct, a second selectable marker is added in a flanking position so that the gene can be represented as: IL-1RN/neo/IL-1RN/TK, where TK is a thymidine kinase gene which can be added to either the IL-1RN 5′ or the IL-1RN 3′ sequence of the preceding construct and which further can be selected against (i.e. is a negative selectable marker) in appropriate media. This two-marker construct allows the selection of homologous recombination events, which removes the flanking TK marker, from non-homologous recombination events which typically retain the TK sequences. The gene deletion and/or replacement can be from the exons, introns, especially intron junctions, and/or the regulatory regions such as promoters.
“Linkage disequilibrium” refers to co-inheritance of two alleles at frequencies greater than would be expected from the separate frequencies of occurrence of each allele in a given control population. The expected frequency of occurrence of two alleles that are inherited independently is the frequency of the first allele multiplied by the frequency of the second allele. Alleles that co-occur at expected frequencies are said to be in “linkage disequilibrium”. The cause of linkage disequilibrium is often unclear. It can be due to selection for certain allele combinations or to recent admixture of genetically heterogeneous populations. In addition, in the case of markers that are very tightly linked to a disease gene, an association of an allele (or group of linked alleles) with the disease gene is expected if the disease mutation occurred in the recent past, so that sufficient time has not elapsed for equilibrium to be achieved through recombination events in the specific chromosomal region. When referring to allelic patterns that are comprised of more than one allele, a first allelic pattern is in linkage disequilibrium with a second allelic pattern if all the alleles that comprise the first allelic pattern are in linkage disequilibrium with at least one of the alleles of the second allelic pattern. An example of linkage disequilibrium is that which occurs between the alleles at the IL-1RN (+2018) and IL-1RN (VNTR) polymorphic sites. The two alleles at IL-1RN (+2018) are 100% in linkage disequilibrium with the two most frequent alleles of IL-1RN (VNTR), which are allele 1 and allele 2.
The term “marker” refers to a sequence in the genome that is known to vary among individuals. For example, the IL-1RN gene has a marker that consists of a variable number of tandem repeats (VNTR).
A “mutated gene” or “mutation” or “functional mutation” refers to an allelic form of a gene, which is capable of altering the phenotype of a subject having the mutated gene relative to a subject which does not have the mutated gene. The altered phenotype caused by a mutation can be corrected or compensated for by certain agents. If a subject must be homozygous for this mutation to have an altered phenotype, the mutation is said to be recessive. If one copy of the mutated gene is sufficient to alter the phenotype of the subject, the mutation is said to be dominant. If a subject has one copy of the mutated gene and has a phenotype that is intermediate between that of a homozygous and that of a heterozygous subject (for that gene), the mutation is said to be co-dominant.
A “non-human animal” of the invention includes mammals such as rodents, non-human primates, sheep, dogs, cows, goats, etc. amphibians, such a s members of the Xenopus genus, and transgenic avians (e.g. chickens, birds, etc.). The term “chimeric animal” is used herein to refer to animals in which the recombinant gene is found, or in which the recombinant gene is expressed in some but not all cells of the animal. The term “tissue-specific chimeric animal” indicates that one of the recombinant IL-1 genes is present and/or expressed or disrupted in some tissues but not others. The term “non-human mammal” refers to any member of the class Mammalia, except for humans.
As used herein, the term “nucleic acid” refers to polynucleotides or oligonucleotides such as deoxyribonucleic acid (DNA), and, where appropriate, ribonucleic acid (RNA). The term should also be understood to include, as equivalents, analogs of either RNA or DNA made from nucleotide analogs (e.g. peptide nucleic acids) and as applicable to the embodiment being described, single (sense or antisense) and double-stranded polynucleotides.
The term “osteoporosis” is defined by the World Health Organization as “ . . . a systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture” (WHO Consensus Development Conference 1993). The clinical definition of osteoporosis is a condition in which the bone mineral density (BMD) or bone mineral concentration (BMC) is greater than about 2.5 standard deviations (SD) below the mean of young healthy women. Severe osteoporosis is defined as having a BMD or BMC greater than about 2.5 SD below the mean of young healthy women and the presence of one or more fragility fractures. Since bone loss is not strictly confined to specific sites, osteoporosis can manifest itself in various ways including alveolar, femoral, radial, vertebral or wrist bone loss or fracture incidence, postmenopausal bone loss, severely reduced bone mass, fracture incidence or rate of bone loss.
The term “polymorphism” refers to the coexistence of more than one form of a gene or portion (e.g., allelic variant) thereof. A portion of a gene of which there are at least two different forms, i.e., two different nucleotide sequences, is referred to as a “polymorphic region of a gene”. A specific genetic sequence at a polymorphic region of a gene is an allele. A polymorphic region can be a single nucleotide, the identity of which differs in different alleles. A polymorphic region can also be several nucleotides long.
The term “propensity to disease,” also “predisposition” or “susceptibility” to disease or any similar phrase, means that certain alleles are hereby discovered to be associated with or predictive of a subject's incidence of developing a particular disease (e.g. a vascular disease). The alleles are thus over-represented in frequency in individuals with disease as compared to healthy individuals. Thus, these alleles can be used to predict disease even in pre-symptomatic or pre-diseased individuals.
“Small molecule” as used herein, is meant to refer to a composition, which has a molecular weight of less than about 5 kD and most preferably less than about 4 kD. Small molecules can be nucleic acids, peptides, peptidomimetics, carbohydrates, lipids or other organic or inorganic molecules.
As used herein, the term “specifically hybridizes” or “specifically detects” refers to the ability of a nucleic acid molecule to hybridize to at least approximately 6 consecutive nucleotides of a sample nucleic acid.
“Transcriptional regulatory sequence” is a generic term used throughout the specification to refer to DNA sequences, such as initiation signals, enhancers, and promoters, which induce or control transcription of protein coding sequences with which they are operably linked.
As used herein, the term “transgene” means a nucleic acid sequence (encoding, e.g., one of the IL-1 polypeptides, or an antisense transcript thereto) which has been introduced into a cell. A transgene could be partly or entirely heterologous, i.e., foreign, to the transgenic animal or cell into which it is introduced, or, is homologous to an endogenous gene of the transgenic animal or cell into which it is introduced, but which is designed to be inserted, or is inserted, into the animal's genome in such a way as to alter the genome of the cell into which it is inserted (e.g., it is inserted at a location which differs from that of the natural gene or its insertion results in a knockout). A transgene can also be present in a cell in the form of an episome. A transgene can include one or more transcriptional regulatory sequences and any other nucleic acid, such as introns, that may be necessary for optimal expression of a selected nucleic acid.
A “transgenic animal” refers to any animal, preferably a non-human mammal, bird or an amphibian, in which one or more of the cells of the animal contain heterologous nucleic acid introduced by way of human intervention, such as by transgenic techniques well known in the art. The nucleic acid is introduced into the cell, directly or indirectly by introduction into a precursor of the cell, by way of deliberate genetic manipulation, such as by microinjection or by infection with a recombinant virus. The term genetic manipulation does not include classical cross-breeding, or in vitro fertilization, but rather is directed to the introduction of a recombinant DNA molecule. This molecule may be integrated within a chromosome, or it may be extrachromosomally replicating DNA. In the typical transgenic animals described herein, the transgene causes cells to express a recombinant form of one of an IL-1 polypeptide, e.g. either agonistic or antagonistic forms. However, transgenic animals in which the recombinant gene is silent are also contemplated, as for example, the FLP or CRE recombinase dependent constructs described below. Moreover, “transgenic animal” also includes those recombinant animals in which gene disruption of one or more genes is caused by human intervention, including both recombination and antisense techniques. The term is intended to include all progeny generations. Thus, the founder animal and all F1, F2, F3, and so on, progeny thereof are included.
The term “treating” as used herein is intended to encompass curing as well as ameliorating at least one symptom of a condition or disease.
The term “vector” refers to a nucleic acid molecule, which is capable of transporting another nucleic acid to which it has been linked. One type of preferred vector is an episome, i.e., a nucleic acid capable of extra-chromosomal replication. Preferred vectors are those capable of autonomous replication and/or expression of nucleic acids to which they are linked Vectors capable of directing the expression of genes to which they are operatively linked are referred to herein as “expression vectors”. In general, expression vectors of utility in recombinant DNA techniques are often in the form of “plasmids” which refer generally to circular double stranded DNA loops which, in their vector form are not bound to the chromosome. In the present specification, “plasmid” and “vector” are used interchangeably as the plasmid is the most commonly used form of vector. However, the invention is intended to include such other forms of expression vectors which serve equivalent functions and which become known in the art subsequently hereto.
The term “wild-type allele” refers to an allele of a gene which, when present in two copies in a subject results in a wild-type phenotype. There can be several different wild-type alleles of a specific gene, since certain nucleotide changes in a gene may not affect the phenotype of a subject having two copies of the gene with the nucleotide changes.
Identifying IL-2 Alleles and Haplotypes
The present invention is based at least in part, on the identification of certain alleles that have been determined to be in association (to a statistically significant extent) to bone loss, fracture risk or other indicators of osteoporosis. Therefore, detection of the alleles can indicate that the subject has or is predisposed to the development of osteoporosis. However, because these alleles are in linkage disequilibrium with other alleles, the detection of such other linked alleles can also indicate that the subject has or is predisposed to the development of a particular disease or condition. For example, the 44112332 haplotype comprises the following genotype:
Three other polymorphisms in an IL-1RN alternative exon (Exon 1ic, which produces an intracellular form of the gene product) are also in linkage disequilibrium with allele 2 of IL-1RN (VNTR) (Clay et al., (1996) Hum Genet. 97:723-26). These include: IL-1RN exon 1ic (1812) (GenBank:X77090 at 1812); the IL-1RN exon 1ic (1868) polymorphism (GenBank:X77090 at 1868); and the IL-1RN exon 1ic (1887) polymorphism (GenBank:X77090 at 1887). Furthermore yet another polymorphism in the promoter for the alternatively spliced intracellular form of the gene, the Pic (1731) polymorphism (GenBank:X77090 at 1731), is also in linkage disequilibrium with allele 2 of the IL-1RN (VNTR) polymorphic locus. For each of these polymorphic loci, the allele 2 sequence variant has been determined to be in linkage disequilibrium with allele 2 of the IL-1RN (VNTR) locus (Clay et al., (1996) Hum Genet. 97:723-26).
The 33221461 haplotype comprises the following genotype:
Individuals with the 44112332 haplotype are typically overproducers of both IL-1α and IL-1β proteins, upon stimulation. In contrast, individuals with the 33221461 haplotype are typically underproducers of IL-1ra. Each haplotype results in a net proinflammatory response. Each allele within a haplotype may have an effect, as well as a composite genotype effect. In addition, particular diseases may be associated with both haplotype patterns.
In addition to the allelic patterns described above, as described herein, one of skill in the art can readily identify other alleles (including polymorphisms and mutations) that are in linkage disequilibrium with an allele associated with osteoporosis. For example, a nucleic acid sample from a first group of subjects without osteoporosis can be collected, as well as DNA from a second group of subjects with the disorder. The nucleic acid sample can then be compared to identify those alleles that are over-represented in the second group as compared with the first group, wherein such alleles are presumably associated with osteoporosis. Alternatively, alleles that are in linkage disequilibrium with an allele that is associated with osteoporosis can be identified, for example, by genotyping a large population and performing statistical analysis to determine which alleles appear more commonly together than expected. Preferably, the group is chosen to be comprised of genetically related individuals. Genetically related individuals include individuals from the same race, the same ethnic group, or even the same family. As the degree of genetic relatedness between a control group and a test group increases, so does the predictive value of polymorphic alleles which are ever more distantly linked to a disease-causing allele. This is because less evolutionary time has passed to allow polymorphisms which are linked along a chromosome in a founder population to redistribute through genetic cross-over events. Thus race-specific, ethnic-specific, and even family-specific diagnostic genotyping assays can be developed to allow for the detection of disease alleles which arose at ever more recent times in human evolution, e.g., after divergence of the major human races, after the separation of human populations into distinct ethnic groups, and even within the recent history of a particular family line.
Linkage disequilibrium between two polymorphic markers or between one polymorphic marker and a disease-causing mutation is a meta-stable state. Absent selective pressure or the sporadic linked reoccurrence of the underlying mutational events, the polymorphisms will eventually become disassociated by chromosomal recombination events and will thereby reach linkage equilibrium through the course of human evolution. Thus, the likelihood of finding a polymorphic allele in linkage disequilibrium with a disease or condition may increase with changes in at least two factors: decreasing physical distance between the polymorphic marker and the disease-causing mutation, and decreasing number of meiotic generations available for the dissociation of the linked pair. Consideration of the latter factor suggests that, the more closely related two individuals are, the more likely they will share a common parental chromosome or chromosomal region containing the linked polymorphisms and the less likely that this linked pair will have become unlinked through meiotic cross-over events occurring each generation. As a result, the more closely related two individuals are, the more likely it is that widely spaced polymorphisms may be co-inherited. Thus, for individuals related by common race, ethnicity or family, the reliability of ever more distantly spaced polymorphic loci can be relied upon as an indicator of inheritance of a linked disease-causing mutation.
Appropriate probes may be designed to hybridize to a specific gene of the IL-1 locus, such as IL-1A, IL-1B or IL-1RN or a related gene. These genomic DNA sequences are shown in
For example, examination of the IL-1 region of the human genome in any one of these databases reveals that the IL-1 locus genes are flanked by a centromere proximal polymorphic marker designated microsatellite marker AFM220ze3 at 127.4 cM (centiMorgans) (see GenBank Acc. No. Z17008) and a distal polymorphic marker designated microsatellite anchor marker AFM087xa1 at 127.9 cM (see GenBank Acc. No. Z16545). These human polymorphic loci are both CA dinucleotide repeat microsatellite polymorphisms, and, as such, show a high degree of heterozygosity in human populations. For example, one allele of AFM220ze3 generates a 211 bp PCR amplification product with a 5′ primer of the sequence TGTACCTAAGCCCACCCTTTAGAGC (SEQ ID No. 4) and a 3′ primer of the sequence TGGCCTCCAGAAACCTCCAA (SEQ ID No. 5). Furthermore, one allele of AFM087xa1 generates a 177 bp PCR amplification product with a 5′ primer of the sequence GCTGATATTCTGGTGGGAAA (SEQ ID No. 6) and a 3′ primer of the sequence GGCAAGAGCAAAACTCTGTC (SEQ ID No. 7). Equivalent primers corresponding to unique sequences occurring 5′ and 3′ to these human chromosome 2 CA dinucleotide repeat polymorphisms will be apparent to one of skill in the art. Reasonable equivalent primers include those which hybridize within about 1 kb of the designated primer, and which further are anywhere from about 17 bp to about 27 bp in length. A general guideline for designing primers for amplification of unique human chromosomal genomic sequences is that they possess a melting temperature of at least about 50° C., wherein an approximate melting temperature can be estimated using the formula Tmelt=[2×(# of A or T)+4×(# of G or C)].
A number of other human polymorphic loci occur between these two CA dinucleotide repeat polymorphisms and provide additional targets for determination of a prognostic allele in a family or other group of genetically related individuals. For example, the National Center for Biotechnology Information web site (www.ncbi.nlm.nih.gov/genemap/) lists a number of polymorphism markers in the region of the IL-1 locus and provides guidance in designing appropriate primers for amplification and analysis of these markers.
Accordingly, the nucleotide segments of the invention may be used for their ability to selectively form duplex molecules with complementary stretches of human chromosome 2 q 12-13 or cDNAs from that region or to provide primers for amplification of DNA or cDNA from this region. The design of appropriate probes for this purpose requires consideration of a number of factors. For example, fragments having a length of between 10, 15, or 18 nucleotides to about 20, or to about 30 nucleotides, will find particular utility. Longer sequences, e.g., 40, 50, 80, 90, 100, even up to full length, are even more preferred for certain embodiments. Lengths of oligonucleotides of at least about 18 to 20 nucleotides are well accepted by those of skill in the art as sufficient to allow sufficiently specific hybridization so as to be useful as a molecular probe. Furthermore, depending on the application envisioned, one will desire to employ varying conditions of hybridization to achieve varying degrees of selectivity of probe towards target sequence. For applications requiring high selectivity, one will typically desire to employ relatively stringent conditions to form the hybrids. For example, relatively low salt and/or high temperature conditions, such as provided by 0.02 M-0.15M NaCl at temperatures of about 50° C. to about 70° C. Such selective conditions may tolerate little, if any, mismatch between the probe and the template or target strand.
Other alleles or other indicia of a disorder can be detected or monitored in a subject in conjunction with detection of the alleles described above, for example, identifying vessel wall thickness (e.g. as measured by ultrasound), or whether the subject smokes, drinks is overweight, is under stress or exercises.
Detection of Alleles
Many methods are available for detecting specific alleles at human polymorphic loci. The preferred method for detecting a specific polymorphic allele will depend, in part, upon the molecular nature of the polymorphism. For example, the various allelic forms of the polymorphic locus may differ by a single base-pair of the DNA. Such single nucleotide polymorphisms (or SNPs) are major contributors to genetic variation, comprising some 80% of all known polymorphisms, and their density in the human genome is estimated to be on average 1 per 1,000 base pairs. SNPs are most frequently biallelic-occurring in only two different forms (although up to four different forms of an SNP, corresponding to the four different nucleotide bases occurring in DNA, are theoretically possible). Nevertheless, SNPs are mutationally more stable than other polymorphisms, making them suitable for association studies in which linkage disequilibrium between markers and an unknown variant is used to map disease-causing mutations. In addition, because SNPs typically have only two alleles, they can be genotyped by a simple plus/minus assay rather than a length measurement, making them more amenable to automation.
A variety of methods are available for detecting the presence of a particular single nucleotide polymorphic allele in an individual. Advancements in this field have provided accurate, easy, and inexpensive large-scale SNP genotyping. Most recently, for example, several new techniques have been described including dynamic allele-specific hybridization (DASH), microplate array diagonal gel electrophoresis (MADGE), pyrosequencing, oligonucleotide-specific ligation, the TaqMan system as well as various DNA “chip” technologies such as the Affymetrix SNP chips. These methods require amplification of the target genetic region, typically by PCR. Still other newly developed methods, based on the generation of small signal molecules by invasive cleavage followed by mass spectrometry or immobilized padlock probes and rolling-circle amplification, might eventually eliminate the need for PCR. Several of the methods known in the art for detecting specific single nucleotide polymorphisms are summarized below. The method of the present invention is understood to include all available methods.
Several methods have been developed to facilitate analysis of single nucleotide polymorphisms. In one embodiment, the single base polymorphism can be detected by using a specialized exonuclease-resistant nucleotide, as disclosed, e.g., in Mundy, C. R. (U.S. Pat. No. 4,656,127). According to the method, a primer complementary to the allelic sequence immediately 3′ to the polymorphic site is permitted to hybridize to a target molecule obtained from a particular animal or human. If the polymorphic site on the target molecule contains a nucleotide that is complementary to the particular exonuclease-resistant nucleotide derivative present, then that derivative will be incorporated onto the end of the hybridized primer. Such incorporation renders the primer resistant to exonuclease, and thereby permits its detection. Since the identity of the exonuclease-resistant derivative of the sample is known, a finding that the primer has become resistant to exonucleases reveals that the nucleotide present in the polymorphic site of the target molecule was complementary to that of the nucleotide derivative used in the reaction. This method has the advantage that it does not require the determination of large amounts of extraneous sequence data.
In another embodiment of the invention, a solution-based method is used for determining the identity of the nucleotide of a polymorphic site. Cohen, D. et al. (French Patent 2,650,840; PCT Appln. No. WO91/02087). As in the Mundy method of U.S. Pat. No. 4,656,127, a primer is employed that is complementary to allelic sequences immediately 3′ to a polymorphic site. The method determines the identity of the nucleotide of that site using labeled dideoxynucleotide derivatives, which, if complementary to the nucleotide of the polymorphic site will become incorporated onto the terminus of the primer.
An alternative method, known as Genetic Bit Analysis or GBA™ is described by Goelet, P. et al. (PCT Appln. No. 92/15712). The method of Goelet, P. et al. uses mixtures of labeled terminators and a primer that is complementary to the sequence 3′ to a polymorphic site. The labeled terminator that is incorporated is thus determined by, and complementary to, the nucleotide present in the polymorphic site of the target molecule being evaluated. In contrast to the method of Cohen et al. (French Patent 2,650,840; PCT Appln. No. WO91/02087) the method of Goelet, P. et al. is preferably a heterogeneous phase assay, in which the primer or the target molecule is immobilized to a solid phase.
Recently, several primer-guided nucleotide incorporation procedures for assaying polymorphic sites in DNA have been described (Komher, J. S. et al., Nucl. Acids. Res. 17:7779-7784 (1989); Sokolov, B. P., Nucl. Acids Res. 18:3671 (1990); Syvanen, A.-C., et al., Genomics 8:684-692 (1990); Kuppuswamy, M. N. et al., Proc. Natl. Acad. Sci. (U.S.A.) 88:1143-1147 (1991); Prezant, T. R. et al., Hum. Mutat. 1:159-164 (1992); Ugozzoli, L. et al., GATA 9:107-112 (1992); Nyren, P. et al., Anal. Biochem. 208:171-175 (1993)). These methods differ from GBA™ in that they all rely on the incorporation of labeled deoxynucleotides to discriminate between bases at a polymorphic site. In such a format, since the signal is proportional to the number of deoxynucleotides incorporated, polymorphisms that occur in runs of the same nucleotide can result in signals that are proportional to the length of the run (Syvanen, A.-C., et al., Amer. J. Hum. Genet. 52:46-59 (1993)).
For mutations that produce premature termination of protein translation, the protein truncation test (PTT) offers an efficient diagnostic approach (Roest, et. al., (1993) Hum. Mol. Genet. 2:1719-21; van der Luijt, et. al., (1994) Genomics 20:1-4). For PTT, RNA is initially isolated from available tissue and reverse-transcribed, and the segment of interest is amplified by PCR. The products of reverse transcription PCR are then used as a template for nested PCR amplification with a primer that contains an RNA polymerase promoter and a sequence for initiating eukaryotic translation. After amplification of the region of interest, the unique motifs incorporated into the primer permit sequential in vitro transcription and translation of the PCR products. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis of translation products, the appearance of truncated polypeptides signals the presence of a mutation that causes premature termination of translation. In a variation of this technique, DNA (as opposed to RNA) is used as a PCR template when the target region of interest is derived from a single exon.
Any cell type or tissue may be utilized to obtain nucleic acid samples for use in the diagnostics described herein. In a preferred embodiment, the DNA sample is obtained from a bodily fluid, e.g, blood, obtained by known techniques (e.g. venipuncture) or saliva. Alternatively, nucleic acid tests can be performed on dry samples (e.g. hair or skin). When using RNA or protein, the cells or tissues that may be utilized must express an IL-1 gene.
Diagnostic procedures may also be performed in situ directly upon tissue sections (fixed and/or frozen) of patient tissue obtained from biopsies or resections, such that no nucleic acid purification is necessary. Nucleic acid reagents may be used as probes and/or primers for such in situ procedures (see, for example, Nuovo, G. J., 1992, PCR in situ hybridization: protocols and applications, Raven Press, NY).
In addition to methods which focus primarily on the detection of one nucleic acid sequence, profiles may also be assessed in such detection schemes. Fingerprint profiles may be generated, for example, by utilizing a differential display procedure, Northern analysis and/or RT-PCR.
A preferred detection method is allele specific hybridization using probes overlapping a region of at least one allele of an IL-1 proinflammatory haplotype and having about 5, 10, 20, 25, or 30 nucleotides around the mutation or polymorphic region. In a preferred embodiment of the invention, several probes capable of hybridizing specifically to other allelic variants involved in a osteoporosis are attached to a solid phase support, e.g., a “chip” (which can hold up to about 250,000 oligonucleotides). Oligonucleotides can be bound to a solid support by a variety of processes, including lithography. Mutation detection analysis using these chips comprising oligonucleotides, also termed “DNA probe arrays” is described e.g., in Cronin et al. (1996) Human Mutation 7:244. In one embodiment, a chip comprises all the allelic variants of at least one polymorphic region of a gene. The solid phase support is then contacted with a test nucleic acid and hybridization to the specific probes is detected. Accordingly, the identity of numerous allelic variants of one or more genes can be identified in a simple hybridization experiment.
These techniques may also comprise the step of amplifying the nucleic acid before analysis. Amplification techniques are known to those of skill in the art and include, but are not limited to cloning, polymerase chain reaction (PCR), polymerase chain reaction of specific alleles (ASA), ligase chain reaction (LCR), nested polymerase chain reaction, self sustained sequence replication (Guatelli, J. C. et al., 1990, Proc. Natl. Acad. Sci. USA 87:1874-1878), transcriptional amplification system (Kwoh, D. Y. et al., 1989, Proc. Natl. Acad. Sci. USA 86:1173-1177), and Q-Beta Replicase (Lizardi, P. M. et al., 1988, Bio/Technology 6:1197).
Amplification products may be assayed in a variety of ways, including size analysis, restriction digestion followed by size analysis, detecting specific tagged oligonucleotide primers in the reaction products, allele-specific oligonucleotide (ASO) hybridization, allele specific 5′ exonuclease detection, sequencing, hybridization, and the like.
PCR based detection means can include multiplex amplification of a plurality of markers simultaneously. For example, it is well known in the art to select PCR primers to generate PCR products that do not overlap in size and can be analyzed simultaneously. Alternatively, it is possible to amplify different markers with primers that are differentially labeled and thus can each be differentially detected. Of course, hybridization based detection means allow the differential detection of multiple PCR products in a sample. Other techniques are known in the art to allow multiplex analyses of a plurality of markers.
In a merely illustrative embodiment, the method includes the steps of (i) collecting a sample of cells from a patient, (ii) isolating nucleic acid (e.g., genomic, mRNA or both) from the cells of the sample, (iii) contacting the nucleic acid sample with one or more primers which specifically hybridize 5′ and 3′ to at least one allele of an IL-1 proinflammatory haplotype under conditions such that hybridization and amplification of the allele occurs, and (iv) detecting the amplification product. These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present in very low numbers.
In a preferred embodiment of the subject assay, the allele of an IL-1 proinflammatory haplotype is identified by alterations in restriction enzyme cleavage patterns. For example, sample and control DNA is isolated, amplified (optionally), digested with one or more restriction endonucleases, and fragment length sizes are determined by gel electrophoresis.
In yet another embodiment, any of a variety of sequencing reactions known in the art can be used to directly sequence the allele. Exemplary sequencing reactions include those based on techniques developed by Maxim and Gilbert ((1977) Proc. Natl. Acad Sci USA 74:560) or Sanger (Sanger et al (1977) Proc. Nat. Acad. Sci. USA 74:5463). It is also contemplated that any of a variety of automated sequencing procedures may be utilized when performing the subject assays (see, for example Biotechniques (1995) 19:448), including sequencing by mass spectrometry (see, for example PCT publication WO 94/16101; Cohen et al. (1996) Adv Chromatogr 36:127-162; and Griffin et al. (1993) Appl Biochem Biotechnol 38:147-159). It will be evident to one of skill in the art that, for certain embodiments, the occurrence of only one, two or three of the nucleic acid bases need be determined in the sequencing reaction. For instance, A-track or the like, e.g., where only one nucleic acid is detected, can be carried out.
In a further embodiment, protection from cleavage agents (such as a nuclease, hydroxylamine or osmium tetroxide and with piperidine) can be used to detect mismatched bases in RNA/RNA or RNA/DNA or DNA/DNA heteroduplexes (Myers, et al. (1985) Science 230:1242). In general, the art technique of “mismatch cleavage” starts by providing heteroduplexes formed by hybridizing (labeled) RNA or DNA containing the wild-type allele with the sample. The double-stranded duplexes are treated with an agent which cleaves single-stranded regions of the duplex such as which will exist due to base pair mismatches between the control and sample strands. For instance, RNA/DNA duplexes can be treated with RNase and DNA/DNA hybrids treated with S1 nuclease to enzymatically digest the mismatched regions. In other embodiments, either DNA/DNA or RNA/DNA duplexes can be treated with hydroxylamine or osmium tetroxide and with piperidine in order to digest mismatched regions. After digestion of the mismatched regions, the resulting material is then separated by size on denaturing polyacrylamide gels to determine the site of mutation. See, for example, Cotton et al (1988) Proc. Natl. Acad Sci USA 85:4397; and Saleeba et al (1992) Methods Enzymol. 217:286-295. In a preferred embodiment, the control DNA or RNA can be labeled for detection.
In still another embodiment, the mismatch cleavage reaction employs one or more proteins that recognize mismatched base pairs in double-stranded DNA (so called “DNA mismatch repair” enzymes). For example, the mutY enzyme of E. coli cleaves A at G/A mismatches and the thymidine DNA glycosylase from HeLa cells cleaves T at G/T mismatches (Hsu et al. (1994) Carcinogenesis 15:1657-1662). According to an exemplary embodiment, a probe based on an allele of an IL-1 locus haplotype is hybridized to a cDNA or other DNA product from a test cell(s). The duplex is treated with a DNA mismatch repair enzyme, and the cleavage products, if any, can be detected from electrophoresis protocols or the like. See, for example, U.S. Pat. No. 5,459,039.
In other embodiments, alterations in electrophoretic mobility will be used to identify an IL-1 locus allele. For example, single strand conformation polymorphism (SSCP) may be used to detect differences in electrophoretic mobility between mutant and wild type nucleic acids (Orita et al. (1989) Proc Natl. Acad. Sci. USA 86:2766, see also Cotton (1993) Mutat Res 285:125-144; and Hayashi (1992) Genet Anal Tech Appl 9:73-79). Single-stranded DNA fragments of sample and control IL-1 locus alleles are denatured and allowed to renature. The secondary structure of single-stranded nucleic acids varies according to sequence, the resulting alteration in electrophoretic mobility enables the detection of even a single base change. The DNA fragments may be labeled or detected with labeled probes. The sensitivity of the assay may be enhanced by using RNA (rather than DNA), in which the secondary structure is more sensitive to a change in sequence. In a preferred embodiment, the subject method utilizes heteroduplex analysis to separate double stranded heteroduplex molecules on the basis of changes in electrophoretic mobility (Keen et al. (1991) Trends Genet. 7:5).
In yet another embodiment, the movement of alleles in polyacrylamide gels containing a gradient of denaturant is assayed using denaturing gradient gel electrophoresis (DGGE) (Myers et al. (1985) Nature 313:495). When DGGE is used as the method of analysis, DNA will be modified to insure that it does not completely denature, for example by adding a GC clamp of approximately 40 bp of high-melting GC-rich DNA by PCR. In a further embodiment, a temperature gradient is used in place of a denaturing agent gradient to identify differences in the mobility of control and sample DNA (Rosenbaum and Reissner (1987) Biophys Chem 265:12753).
Examples of other techniques for detecting alleles include, but are not limited to, selective oligonucleotide hybridization, selective amplification, or selective primer extension. For example, oligonucleotide primers may be prepared in which the known mutation or nucleotide difference (e.g., in allelic variants) is placed centrally and then hybridized to target DNA under conditions which permit hybridization only if a perfect match is found (Saiki et al. (1986) Nature 324:163); Saiki et al (1989) Proc. Natl. Acad. Sci. USA 86:6230). Such allele specific oligonucleotide hybridization techniques may be used to test one mutation or polymorphic region per reaction when oligonucleotides are hybridized to PCR amplified target DNA or a number of different mutations or polymorphic regions when the oligonucleotides are attached to the hybridizing membrane and hybridized with labelled target DNA.
Alternatively, allele specific amplification technology which depends on selective PCR amplification may be used in conjunction with the instant invention. Oligonucleotides used as primers for specific amplification may carry the mutation or polymorphic region of interest in the center of the molecule (so that amplification depends on differential hybridization) (Gibbs et al (1989) Nucleic Acids Res. 17:2437-2448) or at the extreme 3′ end of one primer where, under appropriate conditions, mismatch can prevent, or reduce polymerase extension (Prossner (1993) Tibtech 11:238. In addition it may be desirable to introduce a novel restriction site in the region of the mutation to create cleavage-based detection (Gasparini et al (1992) Mol. Cell. Probes 6:1). It is anticipated that in certain embodiments amplification may also be performed using Taq ligase for amplification (Barany (1991) Proc. Natl. Acad. Sci. USA 88:189). In such cases, ligation will occur only if there is a perfect match at the 3′ end of the 5′ sequence making it possible to detect the presence of a known mutation at a specific site by looking for the presence or absence of amplification.
In another embodiment, identification of the allelic variant is carried out using an oligonucleotide ligation assay (OLA), as described, e.g., in U.S. Pat. No. 4,998,617 and in Landegren, U. et al. ((1988) Science 241:1077-1080). The OLA protocol uses two oligonucleotides which are designed to be capable of hybridizing to abutting sequences of a single strand of a target. One of the oligonucleotides is linked to a separation marker, e.g., biotinylated, and the other is detectably labeled. If the precise complementary sequence is found in a target molecule, the oligonucleotides will hybridize such that their termini abut, and create a ligation substrate. Ligation then permits the labeled oligonucleotide to be recovered using avidin, or another biotin ligand. Nickerson, D. A. et al. have described a nucleic acid detection assay that combines attributes of PCR and OLA (Nickerson, D. A. et al. (1990) Proc. Natl. Acad. Sci. USA 87:8923-27). In this method, PCR is used to achieve the exponential amplification of target DNA, which is then detected using OLA.
Several techniques based on this OLA method have been developed and can be used to detect alleles of an IL-1 locus haplotype. For example, U.S. Pat. No. 5,593,826 discloses an OLA using an oligonucleotide having 3′-amino group and a 5′-phosphorylated oligonucleotide to form a conjugate having a phosphoramidate linkage. In another variation of OLA described in Tobe et al. ((1996) Nucleic Acids Res 24: 3728), OLA combined with PCR permits typing of two alleles in a single microtiter well. By marking each of the allele-specific primers with a unique hapten, i.e. digoxigenin and fluorescein, each OLA reaction can be detected by using hapten specific antibodies that are labeled with different enzyme reporters, alkaline phosphatase or horseradish peroxidase. This system permits the detection of the two alleles using a high throughput format that leads to the production of two different colors.
Another embodiment of the invention is directed to kits for detecting a predisposition for developing a osteoporosis. This kit may contain one or more oligonucleotides, including 5′ and 3′ oligonucleotides that hybridize 5′ and 3′ to at least one allele of an IL-1 locus haplotype. PCR amplification oligonucleotides should hybridize between 25 and 2500 base pairs apart, preferably between about 100 and about 500 bases apart, in order to produce a PCR product of convenient size for subsequent analysis.
Particularly preferred primers for use in the diagnostic method of the invention include SEQ ID Nos. 1-7.
The design of additional oligonucleotides for use in the amplification and detection of IL-1 polymorphic alleles by the method of the invention is facilitated by the availability of both updated sequence information from human chromosome 2q13—which contains the human IL-1 locus, and updated human polymorphism information available for this locus. For example, the DNA sequence for the IL-1A, IL-1B and IL-1RN included GenBank Accession No. X03833 2, GenBank Accession No. X0450 and GenBank Accession No. X64532 respectively. Suitable primers for the detection of a human polymorphism in these genes can be readily designed using this sequence information and standard techniques known in the art for the design and optimization of primers sequences. Optimal design of such primer sequences can be achieved, for example, by the use of commercially available primer selection programs such as Primer 2.1, Primer 3 or GeneFisher (See also, Nicklin M. H. J., Weith A. Duff G. W., “A Physical Map of the Region Encompassing the Human Interleukin-1α, interleukin-1β, and Interleukin-1 Receptor Antagonist Genes” Genomics 19: 382 (1995); Nothwang H. G., et al. “Molecular Cloning of the Interleukin-1 gene Cluster: Construction of an Integrated YAC/PAC Contig and a partial transcriptional Map in the Region of Chromosome 2q13” Genomics 41: 370 (1997); Clark, et al. (1986) Nucl. Acids. Res., 14:7897-7914 [published erratum appears in Nucleic Acids Res., 15:868 (1987) and the Genome Database (GDB) project at the URL http://www.gdb.org).
For use in a kit, oligonucleotides may be any of a variety of natural and/or synthetic compositions such as synthetic oligonucleotides, restriction fragments, cDNAs, synthetic peptide nucleic acids (PNAs), and the like. The assay kit and method may also employ labeled oligonucleotides to allow ease of identification in the assays. Examples of labels which may be employed include radio-labels, enzymes, fluorescent compounds, streptavidin, avidin, biotin, magnetic moieties, metal binding moieties, antigen or antibody moieties, and the like.
The kit may, optionally, also include DNA sampling means. DNA sampling means are well known to one of skill in the art and can include, but not be limited to substrates, such as filter papers, the AmpliCard™ (University of Sheffield, Sheffield, England S10 2JF; Tarlow, J W, et al., J. of Invest. Dermatol. 103:387-389 (1994)) and the like; DNA purification reagents such as Nucleon™ kits, lysis buffers, proteinase solutions and the like; PCR reagents, such as 10× reaction buffers, thermostable polymerase, dNTPs, and the like; and allele detection means such as the HinfI restriction enzyme, allele specific oligonucleotides, degenerate oligonucleotide primers for nested PCR from dried blood.
Pharmacogenomics
Knowledge of the particular alleles associated with a susceptibility to developing osteoporosis, alone or in conjunction with information on other genetic defects contributing to the same condition allows a customization of the prevention or treatment in accordance with the individual's genetic profile, the goal of “pharmacogenomics”. Thus, comparison of an individual's IL-1 profile to the population profile for osteoporosis, permits the selection or design of drugs or other therapeutic regimens that are expected to be safe and efficacious for a particular patient or patient population (i.e., a group of patients having the same genetic alteration).
In addition, the ability to target populations expected to show the highest clinical benefit, based on genetic profile can enable: 1) the repositioning of already marketed drugs; 2) the rescue of drug candidates whose clinical development has been discontinued as a result of safety or efficacy limitations, which are patient subgroup-specific; and 3) an accelerated and less costly development for candidate therapeutics and more optimal drug labeling (e.g. since measuring the effect of various doses of an agent on the causative mutation is useful for optimizing effective dose).
The treatment of an individual with a particular therapeutic can be monitored by determining protein (e.g. IL-1α, IL-1β, or IL-1Ra), mRNA and/or transcriptional level. Depending on the level detected, the therapeutic regimen can then be maintained or adjusted (increased or decreased in dose). In a preferred embodiment, the effectiveness of treating a subject with an agent comprises the steps of: (i) obtaining a preadministration sample from a subject prior to administration of the agent; (ii) detecting the level or amount of a protein, mRNA or genomic DNA in the preadministration sample; (iii) obtaining one or more post-administration samples from the subject; (iv) detecting the level of expression or activity of the protein, mRNA or genomic DNA in the post-administration sample; (v) comparing the level of expression or activity of the protein, mRNA or genomic DNA in the preadministration sample with the corresponding protein, mRNA or genomic DNA in the postadministration sample, respectively; and (vi) altering the administration of the agent to the subject accordingly.
Cells of a subject may also be obtained before and after administration of a therapeutic to detect the level of expression of genes other than an IL-1 gene to verify that the therapeutic does not increase or decrease the expression of genes which could be deleterious. This can be done, e.g., by using the method of transcriptional profiling. Thus, mRNA from cells exposed in vivo to a therapeutic and mRNA from the same type of cells that were not exposed to the therapeutic could be reverse transcribed and hybridized to a chip containing DNA from numerous genes, to thereby compare the expression of genes in cells treated and not treated with the therapeutic.
Osteoporosis Therapeutics
Osteoporosis therapeutics refers to any agent or therapeutic regimen (including pharmaceuticals, nutraceuticals and surgical means) that prevents or postpones the development of or alleviates the symptoms of osteoporosis in the subject. The therapeutic can be a polypeptide, peptidomimetic, nucleic acid or other inorganic or organic molecule, preferably a “small molecule” including vitamins, minerals and other nutrients. Preferably the therapeutic can modulate at least one activity of an IL-1 polypeptide, e.g., interaction with a receptor, by mimicking or potentiating (agonizing) or inhibiting (antagonizing) the effects of a naturally-occurring polypeptide. An agonist can be a wild-type protein or derivative thereof having at least one bioactivity of the wild-type, e.g., receptor binding activity. An agonist can also be a compound that upregulates expression of a gene or which increases at least one bioactivity of a protein. An agonist can also be a compound which increases the interaction of a polypeptide with another molecule, e.g., a receptor. An antagonist can be a compound which inhibits or decreases the interaction between a protein and another molecule, e.g., a receptor or an agent that blocks signal transduction or post-translation processing (e.g., IL-1 converting enzyme (ICE) inhibitor). Accordingly, a preferred antagonist is a compound which inhibits or decreases binding to a receptor and thereby blocks subsequent activation of the receptor. An antagonist can also be a compound that downregulates expression of a gene or which reduces the amount of a protein present. The antagonist can be a dominant negative form of a polypeptide, e.g., a form of a polypeptide which is capable of interacting with a target peptide, e.g., a receptor, but which does not promote the activation of the receptor. The antagonist can also be a nucleic acid encoding a dominant negative form of a polypeptide, an antisense nucleic acid, or a ribozyme capable of interacting specifically with an RNA. Yet other antagonists are molecules which bind to a polypeptide and inhibit its action. Such molecules include peptides, e.g., forms of target peptides which do not have biological activity, and which inhibit binding to receptors. Thus, such peptides will bind to the active site of a protein and prevent it from interacting with target peptides. Yet other antagonists include antibodies that specifically interact with an epitope of a molecule, such that binding interferes with the biological function of the polypeptide. In yet another preferred embodiment, the antagonist is a small molecule, such as a molecule capable of inhibiting the interaction between a polypeptide and a target receptor. Alternatively, the small molecule can function as an antagonist by interacting with sites other than the receptor binding site.
Modulators of IL-1 (e.g. IL-1α, IL-1β or IL-1 receptor antagonist) or a protein encoded by a gene that is in linkage disequilibrium with an IL-1 gene can comprise any type of compound, including a protein, peptide, peptidomimetic, small molecule, or nucleic acid. Preferred agonists include nucleic acids (e.g. encoding an IL-1 protein or a gene that is up- or down-regulated by an IL-1 protein), proteins (e.g. IL-1 proteins or a protein that is up- or down-regulated thereby) or a small molecule (e.g. that regulates expression or binding of an IL-1 protein). Preferred antagonists, which can be identified, for example, using the assays described herein, include nucleic acids (e.g. single (antisense) or double stranded (triplex) DNA or PNA and ribozymes), protein (e.g. antibodies) and small molecules that act to suppress or inhibit IL-1 transcription and/or protein activity.
Effective Dose
Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining The LD50 (the dose lethal to 50% of the population) and the Ed50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Compounds which exhibit large therapeutic indices are preferred. While compounds that exhibit toxic side effects may be used, care should be taken to design a delivery system that targets such compounds to the site of affected tissues in order to minimize potential damage to uninfected cells and, thereby, reduce side effects.
The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the method of the invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose may be formulated in animal models to achieve a circulating plasma concentration range that includes the IC50 (i.e., the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma may be measured, for example, by high performance liquid chromatography.
Formulation and Use
Compositions for use in accordance with the present invention may be formulated in a conventional manner using one or more physiologically acceptable carriers or excipients. Thus, the compounds and their physiologically acceptable salts and solvates may be formulated for administration by, for example, injection, inhalation or insufflation (either through the mouth or the nose) or oral, buccal, parenteral or rectal administration.
For such therapy, the compounds of the invention can be formulated for a variety of loads of administration, including systemic and topical or localized administration. Techniques and formulations generally may be found in Remington's Pharmaceutical Sciences, Meade Publishing Co., Easton, Pa. For systemic administration, injection is preferred, including intramuscular, intravenous, intraperitoneal, and subcutaneous. For injection, the compounds of the invention can be formulated in liquid solutions, preferably in physiologically compatible buffers such as Hank's solution or Ringer's solution. In addition, the compounds may be formulated in solid form and redissolved or suspended immediately prior to use. Lyophilized forms are also included.
For oral administration, the compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g., pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g., lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc or silica); disintegrants (e.g., potato starch or sodium starch glycolate); or wetting agents (e.g., sodium lauryl sulfate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g., sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles (e.g., ationd oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations may also contain buffer salts, flavoring, coloring and sweetening agents as appropriate.
Preparations for oral administration may be suitably formulated to give controlled release of the active compound. For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner. For administration by inhalation, the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from pressurized packs or a nebuliser, with the use of a suitable propellant, e.g., dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas. In the case of a pressurized aerosol the dosage unit may be determined by providing a valve to deliver a metered amount. Capsules and cartridges of e.g., gelatin for use in an inhaler or insufflator may be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.
The compounds may be formulated for parenteral administration by injection, e.g., by bolus injection or continuous infusion. Formulations for injection may be presented in unit dosage form, e.g., in ampoules or in multi-dose containers, with an added preservative. The compositions may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulating agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen-free water, before use.
The compounds may also be formulated in rectal compositions such as suppositories or retention enemas, e.g., containing conventional suppository bases such as cocoa butter or other glycerides.
In addition to the formulations described previously, the compounds may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (for example subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds may be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt. Other suitable delivery systems include microspheres which offer the possibility of local noninvasive delivery of drugs over an extended period of time. This technology utilizes microspheres of precapillary size which can be injected via a coronary catheter into any selected part of the e.g. heart or other organs without causing inflammation or ischemia. The administered therapeutic is slowly released from these microspheres and taken up by surrounding tissue cells (e.g. endothelial cells).
Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration bile salts and fusidic acid derivatives. In addition, detergents may be used to facilitate permeation. Transmucosal administration may be through nasal sprays or using suppositories. For topical administration, the oligomers of the invention are formulated into ointments, salves, gels, or creams as generally known in the art. A wash solution can be used locally to treat an injury or inflammation to accelerate healing.
The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack may for example comprise metal or plastic foil, such as a blister pack. The pack or dispenser device may be accompanied by instructions for administration.
Assays to Identify Therapeutics
Based on the identification of mutations that cause or contribute to the development of osteoporosis, the invention further features cell-based or cell free assays for identifying therapeutics. In one embodiment, a cell expressing an IL-1 receptor, or a receptor for a protein that is encoded by a gene which is in linkage disequilibrium with an IL-1 gene, on the outer surface of its cellular membrane is incubated in the presence of a test compound alone or in the presence of a test compound and another protein and the interaction between the test compound and the receptor or between the protein (preferably a tagged protein) and the receptor is detected, e.g., by using a microphysiometer (McConnell et al. (1992) Science 257:1906). An interaction between the receptor and either the test compound or the protein is detected by the microphysiometer as a change in the acidification of the medium. This assay system thus provides a means of identifying molecular antagonists which, for example, function by interfering with protein-receptor interactions, as well as molecular agonist which, for example, function by activating a receptor.
Cellular or cell-free assays can also be used to identify compounds which modulate expression of an IL-1 gene or a gene in linkage disequilibrium therewith, modulate translation of an mRNA, or which modulate the stability of an mRNA or protein. Accordingly, in one embodiment, a cell which is capable of producing an IL-1, or other protein is incubated with a test compound and the amount of protein produced in the cell medium is measured and compared to that produced from a cell which has not been contacted with the test compound. The specificity of the compound vis a vis the protein can be confirmed by various control analysis, e.g., measuring the expression of one or more control gene. In particular, this assay can be used to determine the efficacy of antisense, ribozyme and triplex compounds.
Cell-free assays can also be used to identify compounds which are capable of interacting with a protein, to thereby modify the activity of the protein. Such a compound can, e.g., modify the structure of a protein thereby effecting its ability to bind to a receptor. In a preferred embodiment, cell-free assays for identifying such compounds consist essentially in a reaction mixture containing a protein and a test compound or a library of test compounds in the presence or absence of a binding partner. A test compound can be, e.g., a derivative of a binding partner, e.g., a biologically inactive target peptide, or a small molecule.
Accordingly, one exemplary screening assay of the present invention includes the steps of contacting a protein or functional fragment thereof with a test compound or library of test compounds and detecting the formation of complexes. For detection purposes, the molecule can be labeled with a specific marker and the test compound or library of test compounds labeled with a different marker. Interaction of a test compound with a protein or fragment thereof can then be detected by determining the level of the two labels after an incubation step and a washing step. The presence of two labels after the washing step is indicative of an interaction.
An interaction between molecules can also be identified by using real-time BIA (Biomolecular Interaction Analysis, Pharmacia Biosensor AB) which detects surface plasmon resonance (SPR), an optical phenomenon. Detection depends on changes in the mass concentration of macromolecules at the biospecific interface, and does not require any labeling of interactants. In one embodiment, a library of test compounds can be immobilized on a sensor surface, e.g., which forms one wall of a micro-flow cell. A solution containing the protein or functional fragment thereof is then flown continuously over the sensor surface. A change in the resonance angle as shown on a signal recording, indicates that an interaction has occurred. This technique is further described, e.g., in BIAtechnology Handbook by Pharmacia.
Another exemplary screening assay of the present invention includes the steps of (a) forming a reaction mixture including: (i) an IL-1 or other protein, (ii) an appropriate receptor, and (iii) a test compound; and (b) detecting interaction of the protein and receptor. A statistically significant change (potentiation or inhibition) in the interaction of the protein and receptor in the presence of the test compound, relative to the interaction in the absence of the test compound, indicates a potential antagonist (inhibitor). The compounds of this assay can be contacted simultaneously. Alternatively, a protein can first be contacted with a test compound for an appropriate amount of time, following which the receptor is added to the reaction mixture. The efficacy of the compound can be assessed by generating dose response curves from data obtained using various concentrations of the test compound. Moreover, a control assay can also be performed to provide a baseline for comparison.
Complex formation between a protein and receptor may be detected by a variety of techniques. Modulation of the formation of complexes can be quantitated using, for example, detectably labeled proteins such as radiolabeled, fluorescently labeled, or enzymatically labeled proteins or receptors, by immunoassay, or by chromatographic detection.
Typically, it will be desirable to immobilize either the protein or the receptor to facilitate separation of complexes from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay. Binding of protein and receptor can be accomplished in any vessel suitable for containing the reactants. Examples include microtitre plates, test tubes, and micro-centrifuge tubes. In one embodiment, a fusion protein can be provided which adds a domain that allows the protein to be bound to a matrix. For example, glutathione-S-transferase fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) or glutathione derivatized microtitre plates, which are then combined with the receptor, e.g. an 35S-labeled receptor, and the test compound, and the mixture incubated under conditions conducive to complex formation, e.g. at physiological conditions for salt and pH, though slightly more stringent conditions may be desired. Following incubation, the beads are washed to remove any unbound label, and the matrix immobilized and radiolabel determined directly (e.g. beads placed in scintillant), or in the supernatant after the complexes are subsequently dissociated. Alternatively, the complexes can be dissociated from the matrix, separated by SDS-PAGE, and the level of protein or receptor found in the bead fraction quantitated from the gel using standard electrophoretic techniques such as described in the appended examples. Other techniques for immobilizing proteins on matrices are also available for use in the subject assay. For instance, either protein or receptor can be immobilized utilizing conjugation of biotin and streptavidin. Transgenic animals can also be made to identify agonists and antagonists or to confirm the safety and efficacy of a candidate therapeutic. Transgenic animals of the invention can include non-human animals containing a restenosis causative mutation under the control of an appropriate endogenous promoter or under the control of a heterologous promoter.
The transgenic animals can also be animals containing a transgene, such as reporter gene, under the control of an appropriate promoter or fragment thereof. These animals are useful, e.g., for identifying drugs that modulate production of an IL-1 protein, such as by modulating gene expression. Methods for obtaining transgenic non-human animals are well known in the art. In preferred embodiments, the expression of the causative mutation is restricted to specific subsets of cells, tissues or developmental stages utilizing, for example, cis-acting sequences that control expression in the desired pattern. In the present invention, such mosaic expression of a protein can be essential for many forms of lineage analysis and can additionally provide a means to assess the effects of, for example, expression level which might grossly alter development in small patches of tissue within an otherwise normal embryo. Toward this end, tissue-specific regulatory sequences and conditional regulatory sequences can be used to control expression of the mutation in certain spatial patterns. Moreover, temporal patterns of expression can be provided by, for example, conditional recombination systems or prokaryotic transcriptional regulatory sequences. Genetic techniques, which allow for the expression of a mutation can be regulated via site-specific genetic manipulation in vivo, are known to those skilled in the art.
The transgenic animals of the present invention all include within a plurality of their cells a causative mutation transgene of the present invention, which transgene alters the phenotype of the “host cell”. In an illustrative embodiment, either the cre/loxP recombinase system of bacteriophage P1 (Lakso et al. (1992) PNAS 89:6232-6236; Orban et al. (1992) PNAS 89:6861-6865) or the FLP recombinase system of Saccharomyces cerevisiae (O'Gorman et al. (1991) Science 251:1351-1355; PCT publication WO 92/15694) can be used to generate in vivo site-specific genetic recombination systems. Cre recombinase catalyzes the site-specific recombination of an intervening target sequence located between loxP sequences. loxP sequences are 34 base pair nucleotide repeat sequences to which the Cre recombinase binds and are required for Cre recombinase mediated genetic recombination. The orientation of loxP sequences determines whether the intervening target sequence is excised or inverted when Cre recombinase is present (Abremski et al. (1984) J. Biol. Chem. 259:1509-1514); catalyzing the excision of the target sequence when the loxP sequences are oriented as direct repeats and catalyzes inversion of the target sequence when loxP sequences are oriented as inverted repeats.
Accordingly, genetic recombination of the target sequence is dependent on expression of the Cre recombinase. Expression of the recombinase can be regulated by promoter elements which are subject to regulatory control, e.g., tissue-specific, developmental stage-specific, inducible or repressible by externally added agents. This regulated control will result in genetic recombination of the target sequence only in cells where recombinase expression is mediated by the promoter element. Thus, the activation of expression of the causative mutation transgene can be regulated via control of recombinase expression.
Use of the cre/loxP recombinase system to regulate expression of a causative mutation transgene requires the construction of a transgenic animal containing transgenes encoding both the Cre recombinase and the subject protein. Animals containing both the Cre recombinase and the restenosis causative mutation transgene can be provided through the construction of “double” transgenic animals. A convenient method for providing such animals is to mate two transgenic animals each containing a transgene.
Similar conditional transgenes can be provided using prokaryotic promoter sequences which require prokaryotic proteins to be simultaneous expressed in order to facilitate expression of the transgene. Exemplary promoters and the corresponding trans-activating prokaryotic proteins are given in U.S. Pat. No. 4,833,080.
Moreover, expression of the conditional transgenes can be induced by gene therapy-like methods wherein a gene encoding the transactivating protein, e.g. a recombinase or a prokaryotic protein, is delivered to the tissue and caused to be expressed, such as in a cell-type specific manner. By this method, the transgene could remain silent into adulthood until “turned on” by the introduction of the transactivator.
In an exemplary embodiment, the “transgenic non-human animals” of the invention are produced by introducing transgenes into the germline of the non-human animal. Embryonal target cells at various developmental stages can be used to introduce transgenes. Different methods are used depending on the stage of development of the embryonal target cell. The specific line(s) of any animal used to practice this invention are selected for general good health, good embryo yields, good pronuclear visibility in the embryo, and good reproductive fitness. In addition, the haplotype is a significant factor. For example, when transgenic mice are to be produced, strains such as C57BL/6 or FVB lines are often used (Jackson Laboratory, Bar Harbor, Me.). Preferred strains are those with H-2b, H-2d or H-2q haplotypes such as C57BL/6 or DBA/1. The line(s) used to practice this invention may themselves be transgenics, and/or may be knockouts (i.e., obtained from animals which have one or more genes partially or completely suppressed).
In one embodiment, the transgene construct is introduced into a single stage embryo. The zygote is the best target for microinjection. In the mouse, the male pronucleus reaches the size of approximately 20 micrometers in diameter which allows reproducible injection of 1-2 pl of DNA solution. The use of zygotes as a target for gene transfer has a major advantage in that in most cases the injected DNA will be incorporated into the host gene before the first cleavage (Brinster et al. (1985) PNAS 82:4438-4442). As a consequence, all cells of the transgenic animal will carry the incorporated transgene. This will in general also be reflected in the efficient transmission of the transgene to offspring of the founder since 50% of the germ cells will harbor the transgene.
Normally, fertilized embryos are incubated in suitable media until the pronuclei appear. At about this time, the nucleotide sequence comprising the transgene is introduced into the female or male pronucleus as described below. In some species such as mice, the male pronucleus is preferred. It is most preferred that the exogenous genetic material be added to the male DNA complement of the zygote prior to its being processed by the ovum nucleus or the zygote female pronucleus. It is thought that the ovum nucleus or female pronucleus release molecules which affect the male DNA complement, perhaps by replacing the protamines of the male DNA with histones, thereby facilitating the combination of the female and male DNA complements to form the diploid zygote. Thus, it is preferred that the exogenous genetic material be added to the male complement of DNA or any other complement of DNA prior to its being affected by the female pronucleus. For example, the exogenous genetic material is added to the early male pronucleus, as soon as possible after the formation of the male pronucleus, which is when the male and female pronuclei are well separated and both are located close to the cell membrane. Alternatively, the exogenous genetic material could be added to the nucleus of the sperm after it has been induced to undergo decondensation. Sperm containing the exogenous genetic material can then be added to the ovum or the decondensed sperm could be added to the ovum with the transgene constructs being added as soon as possible thereafter.
Introduction of the transgene nucleotide sequence into the embryo may be accomplished by any means known in the art such as, for example, microinjection, electroporation, or lipofection. Following introduction of the transgene nucleotide sequence into the embryo, the embryo may be incubated in vitro for varying amounts of time, or reimplanted into the surrogate host, or both. In vitro incubation to maturity is within the scope of this invention. One common method in to incubate the embryos in vitro for about 1-7 days, depending on the species, and then reimplant them into the surrogate host.
For the purposes of this invention a zygote is essentially the formation of a diploid cell which is capable of developing into a complete organism. Generally, the zygote will be comprised of an egg containing a nucleus formed, either naturally or artificially, by the fusion of two haploid nuclei from a gamete or gametes. Thus, the gamete nuclei must be ones which are naturally compatible, i.e., ones which result in a viable zygote capable of undergoing differentiation and developing into a functioning organism. Generally, a euploid zygote is preferred. If an aneuploid zygote is obtained, then the number of chromosomes should not vary by more than one with respect to the euploid number of the organism from which either gamete originated.
In addition to similar biological considerations, physical ones also govern the amount (e.g., volume) of exogenous genetic material which can be added to the nucleus of the zygote or to the genetic material which forms a part of the zygote nucleus. If no genetic material is removed, then the amount of exogenous genetic material which can be added is limited by the amount which will be absorbed without being physically disruptive. Generally, the volume of exogenous genetic material inserted will not exceed about 10 picoliters. The physical effects of addition must not be so great as to physically destroy the viability of the zygote. The biological limit of the number and variety of DNA sequences will vary depending upon the particular zygote and functions of the exogenous genetic material and will be readily apparent to one skilled in the art, because the genetic material, including the exogenous genetic material, of the resulting zygote must be biologically capable of initiating and maintaining the differentiation and development of the zygote into a functional organism.
The number of copies of the transgene constructs which are added to the zygote is dependent upon the total amount of exogenous genetic material added and will be the amount which enables the genetic transformation to occur. Theoretically only one copy is required; however, generally, numerous copies are utilized, for example, 1,000-20,000 copies of the transgene construct, in order to insure that one copy is functional. As regards the present invention, there will often be an advantage to having more than one functioning copy of each of the inserted exogenous DNA sequences to enhance the phenotypic expression of the exogenous DNA sequences.
Any technique which allows for the addition of the exogenous genetic material into nucleic genetic material can be utilized so long as it is not destructive to the cell, nuclear membrane or other existing cellular or genetic structures. The exogenous genetic material is preferentially inserted into the nucleic genetic material by microinjection. Microinjection of cells and cellular structures is known and is used in the art.
Reimplantation is accomplished using standard methods. Usually, the surrogate host is anesthetized, and the embryos are inserted into the oviduct. The number of embryos implanted into a particular host will vary by species, but will usually be comparable to the number of off spring the species naturally produces.
Transgenic offspring of the surrogate host may be screened for the presence and/or expression of the transgene by any suitable method. Screening is often accomplished by Southern blot or Northern blot analysis, using a probe that is complementary to at least a portion of the transgene. Western blot analysis using an antibody against the protein encoded by the transgene may be employed as an alternative or additional method for screening for the presence of the transgene product. Typically, DNA is prepared from tail tissue and analyzed by Southern analysis or PCR for the transgene. Alternatively, the tissues or cells believed to express the transgene at the highest levels are tested for the presence and expression of the transgene using Southern analysis or PCR, although any tissues or cell types may be used for this analysis.
Alternative or additional methods for evaluating the presence of the transgene include, without limitation, suitable biochemical assays such as enzyme and/or immunological assays, histological stains for particular marker or enzyme activities, flow cytometric analysis, and the like. Analysis of the blood may also be useful to detect the presence of the transgene product in the blood, as well as to evaluate the effect of the transgene on the levels of various types of blood cells and other blood constituents.
Progeny of the transgenic animals may be obtained by mating the transgenic animal with a suitable partner, or by in vitro fertilization of eggs and/or sperm obtained from the transgenic animal. Where mating with a partner is to be performed, the partner may or may not be transgenic and/or a knockout; where it is transgenic, it may contain the same or a different transgene, or both. Alternatively, the partner may be a parental line. Where in vitro fertilization is used, the fertilized embryo may be implanted into a surrogate host or incubated in vitro, or both. Using either method, the progeny may be evaluated for the presence of the transgene using methods described above, or other appropriate methods.
The transgenic animals produced in accordance with the present invention will include exogenous genetic material. Further, in such embodiments the sequence will be attached to a transcriptional control element, e.g., a promoter, which preferably allows the expression of the transgene product in a specific type of cell.
Retroviral infection can also be used to introduce the transgene into a non-human animal. The developing non-human embryo can be cultured in vitro to the blastocyst stage. During this time, the blastomeres can be targets for retroviral infection (Jaenich, R. (1976) PNAS 73:1260-1264). Efficient infection of the blastomeres is obtained by enzymatic treatment to remove the zona pellucida (Manipulating the Mouse Embryo, Hogan eds. (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, 1986). The viral vector system used to introduce the transgene is typically a replication-defective retrovirus carrying the transgene (Jahner et al. (1985) PNAS 82:6927-6931; Van der Putten et al. (1985) PNAS 82:6148-6152). Transfection is easily and efficiently obtained by culturing the blastomeres on a monolayer of virus-producing cells (Van der Putten, supra; Stewart et al. (1987) EMBO J. 6:383-388). Alternatively, infection can be performed at a later stage. Virus or virus-producing cells can be injected into the blastocoele (Jahner et al. (1982) Nature 298:623-628). Most of the founders will be mosaic for the transgene since incorporation occurs only in a subset of the cells which formed the transgenic non-human animal. Further, the founder may contain various retroviral insertions of the transgene at different positions in the genome which generally will segregate in the offspring. In addition, it is also possible to introduce transgenes into the germ line by intrauterine retroviral infection of the midgestation embryo (Jahner et al. (1982) supra).
A third type of target cell for transgene introduction is the embryonal stem cell (ES). ES cells are obtained from pre-implantation embryos cultured in vitro and fused with embryos (Evans et al. (1981) Nature 292:154-156; Bradley et al. (1984) Nature 309:255-258; Gossler et al. (1986) PNAS 83: 9065-9069; and Robertson et al. (1986) Nature 322:445-448). Transgenes can be efficiently introduced into the ES cells by DNA transfection or by retrovirus-mediated transduction. Such transformed ES cells can thereafter be combined with blastocysts from a non-human animal. The ES cells thereafter colonize the embryo and contribute to the germ line of the resulting chimeric animal. For review see Jaenisch, R. (1988) Science 240:1468-1474.
The present invention is further illustrated by the following examples which should not be construed as limiting in any way. The practice of the present invention will employ, unless otherwise indicated, conventional techniques that are within the skill of the art. Such techniques are explained fully in the literature. See, for example, Molecular Cloning A Laboratory Manual, (2nd ed., Sambrook, Fritsch and Maniatis, eds., Cold Spring Harbor Laboratory Press: 1989); DNA Cloning, Volumes I and II (D. N. Glover ed., 1985); Oligonucleotide Synthesis (M. J. Gait ed., 1984); U.S. Pat. No. 4,683,195; U.S. Pat. No. 4,683,202; and Nucleic Acid Hybridization (B. D. Hames & S. J. Higgins eds., 1984).
According to some embodiments, the present invention provides for methods of identifying premenopausal, perimenopausal, and/or postmenopausal women who are at risk of developing bone loss at an earlier age. Methods are provided to identify early those individuals at greatest risk for developing osteoporosis so that the individual can be counseled to make appropriate life style changes or institute other therapeutic interventions. For example, calcium supplements and exercise have been shown to be valuable preventive factors if used during a critical early age window. Hormone replacement therapy (HRT) has also been used successfully to combat osteoporosis occurring after menopause. HRT may be of greatest benefit if used early in the disease process before major bone loss has occurred. Since HRT has potentially serious side-effects, it would be useful for women to know their personal risk level for osteoporosis when making decisions about the use of HRT versus other interventions aimed at reducing the risk of developing osteoporosis.
According to some embodiments, the present invention provides for methods for selecting an appropriate therapeutic/dietary regimen or lifestyle recommendation for a subject comprising: identifying in a subject's DNA the IL1A 4845G>T polymorphism, wherein the presence of the IL1A 4845G>T polymorphism indicates that the subject is at greater risk have younger age at menopause and at greater risk for bone fracture at an earlier age. The presence of the IL1A 4845G>T polymorphism in conjunction with a younger age at menopause is further indication that the subject is at greater risk for bone fracture at an earlier age. Appropriate therapeutic/dietary regimen or lifestyle recommendations include, but are not limited to, calcium supplements, exercise, hormone replacement therapy, and combinations and mixtures thereof.
According to some embodiments, the present invention provides for methods for selecting an appropriate therapeutic/dietary regimen or lifestyle recommendation for a subject comprising: identifying in a subject's DNA the IL1B+3877 A>G polymorphism, wherein the presence of the IL1B+3877 A>G polymorphism indicates that the subject is at greater risk have younger age at menopause and at greater risk for bone fracture at an earlier age. The presence of the IL1B+3877 A>G polymorphism in conjunction with a younger age at menopause is further indication that the subject is at greater risk for bone fracture at an earlier age. Appropriate therapeutic/dietary regimen or lifestyle recommendations include, but are not limited to, calcium supplements, exercise, hormone replacement therapy, and combinations and mixtures thereof.
In most industrialized countries, natural menopause occurs on average around the age of 51, but there is a large variation in age at natural menopause (mean age: 51 yrs; range: 39-59 yrs). Younger age at menopause refers to an age prior to the mean age at natural menopause. Younger age may refer to any one of the ages between 39 to 51 years of age (i.e., 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51). Younger age may also be expressed in terms of ranges such as from 39 to 51 years of age, 39 to 42 years of age, 39 to 44 years of age, 39 to 46 years of age, 39 to 48 years of age, 39 to 50 years of age, 44 to 51 years of age, 44 to 50 years of age, 46 to 51 years of age, 46 to 50 years of age, and so on.
Individuals at risk of developing complications associated with menopause (e.g., loss of bone mineral density or bone fracture) at an earlier age generally refers to the period shortly after the onset of menopause. For example, individuals or subjects identified as being at greater risk for developing osteoporosis or complications thereof at an earlier age generally develop these conditions between 0 and 36 months after the onset of menopause. This may include 0 to 3 months after the onset of menopause, 0 to 6 months after the onset of menopause, 0 to 9 months after the onset of menopause, 0 to 12 months after the onset of menopause, 0 to 15 months after the onset of menopause, 0 to 18 months after the onset of menopause, 0 to 24 months after the onset of menopause, 0 to 30 months after the onset of menopause, and/or 0 to 36 months after the onset of menopause. This may also include 6 to 12 months after the onset of menopause, 6 to 18 months after the onset of menopause, 6 to 24 months after the onset of menopause, 6 to 30 months after the onset of menopause, 6 to 36 months after the onset of menopause, 12 to 18 months after the onset of menopause, 12 to 24 months after the onset of menopause, 12 to 30, months after the onset of menopause, 12 to 36 months after the onset of menopause, 18 to 36 months after the onset of menopause, and so on.
A cohort of 1,071 subjects participating in the Study of Osteoporotic Fractures of the University of California at San Francisco Association was genotyped for genotypic markers in the IL-1 gene cluster, using techniques, which are known in the art.
The results of the genotyping are presented in Table 1A. Table 1B presents the results of a Hawaiian osteoporosis study, which is further described below.
In the random sample control cohort of 626 subjects, 185 non-spine fractures had occurred. These subjects were used for the analysis of “non-spine fractures”.
As shown in Table 2, allele 2 of IL-1A (+4845) is associated with an increase in the risk of non-spine fractures. In addition, allele 2 of IL-1B (+3954) is associated with a statistically significant increase in the risk of non-spine fractures. In contrast, allele 2 of IL-1RN (+2018) is associated with a significant decrease in the risk of non-spine fractures. Allele 2 of IL-1A (+4845) is associated with an increase in wrist fractures, although not statistically significant (RR=1.8, 95% CI=1.0-3.5). In the total cohort, allele 2 is associated with an increase in risk of wrist fractures. This effect disappears when HRT users are excluded.
Increase in risk of fractures shows a gene-dose effect for allele 2 of IL-1A (+4845) and IL-1B (+3954). In particular, the more copies of allele 2, the larger the effect. Decrease of risk of fractures also shows a gene-dose effect for allele 2 of IL-1RN (+2018). Specifically, the more copies of allele 2, the larger the effect. As shown in Table 3A, these associations are true for the cohort with exclusion of HRT users. As shown in Table 3B, the associations hold up, though not as strong, when the total cohort, including HRT users, is considered. Hip fractures and vertebral spine fractures, on the other hand, do not appear to be associated with any of the IL-1 genetic markers.
Bone mineral density (BMD) was measured at the calcaneus, distal radius, total hip, femoral neck and spine. The analysis was adjusted for age, bone mineral index (BMI) menopausal status and life style factors. As shown in Tables 4A and 4B, allele 2 of IL-1B (+3954) is associated with significantly higher BMD at the calcaneus, whether HRT users are included or excluded (p<0.05 for trend; p<0.05 for genotype [2.2] vs. genotype [1.1]).
Allele 2 of IL-1B (−511) is significantly associated with a lower BMD at the calcaneus in the total cohort, including HRT users (p<0.05 for trend; p<0.05 for genotype [2.2] vs. genotype [1.1]). Allele 2 of IL-1B (−511) is associated with a trend towards lower BMD at the calcaneus when HRT users are excluded. No consistent pattern of association between IL-1 genotypes and BMD at other sites was found.
Rate of bone loss was measured at total hip, femoral neck and calcaneus. As shown in Tables 4A and 4B, allele 2 of IL-1B (−511) is associated with a higher rate of bone loss at the total hip (p<0.05 for trend), for the total cohort and for the cohort with exclusion of HRT users. Genotype [2.2] of IL-1B (−511) is associated with a trend towards a higher rate of bone loss at the calcaneus. Allele 2 of IL-1B (−511) is associated with a trend towards a higher rate of bone loss at the femoral neck. A gene-dose effect for rate of bone loss at the hip for allele 2 of IL-1B (−511) is present. A similar, though not significant association is observed for rate of bone loss at the femoral neck. These results are similar whether HRT users are included (Table 4A) or excluded (Table 4B) in the analysis.
Hawaiian Osteoporosis Study
100 participants in the Hawaii Osteoporosis Study with fractures and 100 participants without fractures were genotyped for genotypic markers in the IL-1 gene cluster. The results are presented in Table 1B. The participants in the study are all Japanese-American women in their early to mid 80's. The following clinical data were analyzed: spine and non-spine fractures, including and excluding ovariectomies, bone mineral content (BMC) at the distal and proximal radius, and os calcis, including and excluding subjects who had ovariectomies. The analysis was adjusted for age, BMI and duration of estrogen use.
Results
Allele 2 of IL-1A (+4845) is strongly associated with an increase in the number of spine and non-spine fractures (p<0.018), regardless whether subjects with or without ovariectomies were included.
Allele 2 of IL-1B (−511) is associated with a decrease in BMC of the distal radius (p<0.024). Allele 2 of IL-1RN (+2018) is associated with a decrease in BMC at the os calcis (p<0.022).
Discussion of Findings
Role of Ethnicity The distribution of genotypes in the IL-1 gene cluster is very different for Americans with Caucasian ancestry and Japanese-Americans, many of whom in this specific study are first generation immigrants. Distinctly different distribution patterns have been found for other ethnic groups, notably:
Chinese (very low frequency of allele 2 of IL-1RN (+2018) and IL-1B (+3954));
African-Americans (pattern similar to the Japanese population); and
Hispanics (distribution pattern similar to European Caucasians. This is specifically true for Hispanics from European ancestry. However, the pattern is not very different in Mexican Hispanics with European ancestry).
Therefore the genotype of IL-1RN (+2018) may not accurately reflect the biological pattern and response. IL-1B (−511) may be a more accurate indicator for that specific haplotype and genotype pattern. Similarly, IL-1B (+3954) may not be an accurate marker for the haplotype pattern. IL-1A (+4954) may be a more accurate indicator for that specific haplotype and genotype pattern.
Fracture Risk Allele 2 of IL-1A (+4845) and allele 2 of IL-1B (+3954) are associated with increase in fracture risk. This points to an association with haplotype pattern 1 (see
Haplotype pattern 1 results in increased IL-1a and IL-1b levels and bioactivity, but normal IL-1 receptor antagonist levels.
Rate of Bone Loss Rate of bone loss is associated with allele 2 of IL-1B (−511) (Haplotype pattern 2). Haplotype pattern 2 results in normal levels of IL-1, but reduced levels of IL-1 receptor antagonist. The net result is an increase in IL-1 biological activity and response.
Bone Mineral Density BMD (or BMC) is associated with allele 2 of either IL-1B (−511) or IL-1RN (+2018) (Haplotype pattern 2) at the calcaneus, and at the distal radius.
Increase in BMD at the calcaneus is associated with haplotype pattern 2. BMD at other sites is not significantly associated with IL-1 markers in this study, which may be caused by the specifics of the study population resulting in a lack of power in the statistical analysis. Other issues that may play a role in the University of California, San Francisco study population are: better health, better education, participation in the study and a higher socio-economic status.
The process of bone remodeling is regulated by a number of factors, including: bone metabolism, rate of bone loss, peak bone mass, life style factors, genetics, use of prescription drugs and body mass. Osteoporotic fractures are the endpoint in a complex process of bone remodeling, bone loss, and aging. Bone remodeling and thus the likelihood of developing osteoporosis and osteoporotic fractures are regulated by different biological processes at different stages of the life cycle. In the first 5-10 years after onset of menopause most rapid bone loss is experienced due to decrease of estrogen levels and increase of IL-1 levels and activity. In this stage increased formation and activation of osteoclasts (due to increased IL-1 levels) drives the process of bone remodeling. The increase in IL-1 levels in the first 5-10 years after menopause may be more important than levels of IL-1 receptor antagonist. Approximately 10 years after menopause, the rate of bone loss slows down, due to a change in the biology of bone remodeling. In this stage the reduced formation of osteoblasts forms the driving force behind bone remodeling. Reduced levels of IL-1 receptor antagonist may form a more important factor in later postmenopausal years in regulating the amount of bone loss.
Haplotype pattern 1 is associated with increase in IL-1a and IL-1b levels and bioactivity, but normal IL-1 receptor antagonist levels. Women with haplotype pattern 1 are likely to experience a larger bone loss during their early menopausal years than women with haplotype pattern 2. Women with haplotype pattern 1 are thus more likely to experience fractures at any stage of life, when no preventive measures or treatment are initiated.
Women with haplotype pattern 2 will likely experience more bone loss later in life and may be more susceptible to experience fractures later in life, specifically fractures associated with age-related osteoporosis. Therefore, subjects with haplotype pattern 2, who produce constitutively less IL-1ra than subjects with haplotype pattern 1, will experience larger bone loss and reduced bone formation in the later postmenopausal phase of their life.
Based on the hypothesis set forth above, it follows that the data reported by Keen et al. (1998) (“Allelic variation in the interleukin-1 receptor antagonist gene is associated with early postmenopausal bone loss at the spine” (Bone 23 (4), 367-371): an association between allele [1] of the VNTR in IL-1RN and early postmenopausal bone loss) suggest that the subjects who have allele [1] of the VNTR actually carry haplotype pattern 1. Since all of the subjects in this study are within 5 years of onset of menopause, their bone loss is regulated by increased levels and activity of IL-1 and not by increased or decreased levels of IL-1ra. Since only the VNTR of IL-1RN was determined, the erroneous conclusion was reached that VNTR allele 1 of IL-1RN is important in the changes in bone density and is the main predictor for bone loss and risk of osteoporotic fracture incidence.
A second study using a cohort of 2529 (1,240 cases and 1,289 controls) subjects participating in the Study of Osteoporotic Fractures of the University of California at San Francisco Association was genotyped for genotypic markers in the IL-1 gene cluster, using techniques, which are known in the art. Case subjects were selected from the study population on the basis of having radiographic evidence of a prevalent vertebral fracture at baseline examination or the radiographic evidence of developing a fracture, for the first time, during the course of the study.
Additionally, an age matched control sample from the study population is drawn. Control subjects are selected on the basis of the absence of any radiographic evidence of vertebral fractures and the absence of any recorded bone fractures including appendicular and rib fractures during the course of the study.
The use of vertebral fracture as an endpoint for studying genetic predisposition to osteoporosis has certain advantages over the studies described above. Hip and wrist fractures generally require both the development of osteoporosis and the presence of a traumatic event, such as a physical fall. Vertebral fractures occur as a result of osteoporosis without the need for any traumatic event, since the constant weight of the body on the spine will cause individual vertebra to collapse as the bone weakens due to osteoporosis. Vertebral fractures are not obvious to the individual until she notices a loss of height, develops a hunched back appearance, or vertebral collapse impinges a nerve and causes pain. For this reason, studies of vertebral fracture must include precise assessments of radiographs of the spine that are taken on a regular time course that is independent of an individual's awareness of problems, such as the monitoring protocols that were used in the Study of Osteoporotic Fractures.
Patients with known metabolic bone disease
Patients without fracture at baseline who died during the course of the 3.7 years follow up examination.
The DNA was obtained from whole blood that was collected from study subjects in 1988-1989. 5 ml of blood was blotted on a 3×3 inch filter paper, allowed to dry and stored frozen at −20° C.
Genotyping was performed as described by Kornman et al. (1997) (8) and Cox et al. (1998) (9). SNPs in the IL-1A, IL-1B, IL-1RN, VDR, COL1A1, ER, and PTHR genes were genotyped.
Data Analysis: Power Calculations
Power calculations have been conducted assuming 900 cases, 900 controls, an alpha level of 0.01, and a true odds ratio of either 1.5 or 2.0. Statistical significance is readily achieved when the true OR is 2.0 or when the true OR is 1.5 and minor allele frequency in controls is at least 5%. At lower control frequency, an OR of 1.5 requires only a small increase in frequency among cases (e.g., 5% control frequency and 7.3% case frequency).
In addition to assessing statistical significance, an important goal of this study is to characterize the clinical significance of any genetic effect. For this purpose, “clinically significant” means risk is increased by 50% and “highly clinically significant” means we can draw this conclusion assuming a 1% type 1 error rate.
Clinical significance is achieved 50% of the time for a true OR of 1.5, except at low control allele frequency when power is reduced in order to preserve the size of the test. Highly clinically significant results are likely to occur when the true OR is at least 2.0 and more so when minor allele frequencies are not small. Power will be greater for even higher true ORs. For example, at an OR of 2.5, highly clinically significant results would occur with at least 96% power for minor allele frequencies≧15% and with 57% power for a minor allele frequency of exactly 5%.
Clinical data was used for statistical analysis with and without exclusion of individuals who have the following criteria: thyroid hormones, prior use of thiazides, prior use of HRT where data is available, prior use of anabolic steroids, bisphosphonates, SERMs or calcitonin where data is available, and concurrent use of therapy to treat/prevent osteoporosis.
Associations between polymorphisms and osteoporosis were tested by assessing whether allele frequencies at any of the gene SNPs differ in cases and controls. To account for multiple testing, the size of each test is set at 0.01 (Bonferroni correction). Thus, a marker is deemed “statistically significant” if the 99% confidence interval does not contain the null hypothesis. For each marker, the maximum likelihood estimate of the odds ratio (OR) is also obtained and compared to the pre-determined clinically significant value of 1.5. A marker is deemed “clinically significant” if the point estimate of the OR is at least 1.5 and “highly clinically significant” if the lower confidence bound of the OR exceeds the same threshold. In the former case, statistical significance is also required. (The latter, by definition, achieves statistical significance).
Associations between polymorphisms and osteoporosis were further evaluated by testing combinations of polymorphisms. Some specific combinations to be analyzed include alleles at gene SNPs, IL-1A−889, IL-1A+4845, IL-1B−3737, IL-1B−511, IL1B−31, IL-1RN+2018, IL-1RN VNTR, as well as other IL genes and VDR genes, COL1A1 genes, ER genes, and PTHR genes. Additional combinations of alleles were also evaluated. Such further evaluation includes intramarker (genotype analysis) and intermarker (composite genotype or haplotype analysis) comparisons.
Analyses are further refined by adjusting for the following covariates: age, smoking history, BMI, Age of onset of menopause, levels of serum estrogen, levels of osteocalcin, vertebral fracture data, and changes in BMD
The same analytic strategy is used to address any combination of gene polymorphisms, both for known and novel polymorphisms. Synergy among genes was assessed by adding interaction terms to a logistic regression model.
For the purpose of identifying a group with potentially elevated risk of vertebral fracture, IL-1+ was defined to consist of individuals meeting one of three conditions: 1) genotype 2.2 at IL-1A (+4845), genotype 1.1 at IL-1B (−511) and 1.1 genotype at IL-1RN (+2018), 2) genotype 2.2 at IL-1B (−511) and 2.2 genotype at IL-1RN (+2018), or 3) genotype 2.2 at IL-1B (−511) and 1.2 genotype at IL-1RN (+2018). Thirteen percent of the study population was scored as IL-1+, and those classified as IL-1+ had a higher rate of vertebral fracture (p-value<0.05). In women who had never used estrogen replacement therapy, the frequency of IL-1+ was 11% among those without vertebral fracture and 18% among those with vertebral fracture (p-value=0.0001).
Adjusting for age and bone mineral density (BMD) assessed in the neck, the odds ratio (OR) of vertebral fracture for IL-1+ among never estrogen users (i.e., non-estrogen users) was 1.9 (p-value=6×10−5). Given the inclusion of BMD in the statistical model, it was concluded that the effect of an IL-1+ genotype is an independent risk factor for vertebral fracture that provides information above and beyond that of bone mineral density.
Each of the three components comprising the IL-1+ genotype also confers statistically significant risk of vertebral fracture in women who never used estrogen replacement therapy. Adjusting for age and BMD, those with genotype 2.2 at IL-1A (+4845), genotype 1.1 at IL-1B (−511) and 1.1 genotype at IL-1RN (+2018) have an OR=2.0 (p-value=0.004), those with genotype 2.2 at IL-1B (−511) and 2.2 genotype at IL-1RN (+2018) have an OR=2.2 (p-value=0.01), and those with genotype 2.2 at IL-1B (−511) and 1.2 genotype at IL-1RN (+2018) have an OR=1.7 (p-value=0.01).
Vertebral deformities, due to fractures, are a common clinical manifestation of osteoporosis and which often leads to back pain, disabilities, kyphosis and subsequent fractures. Although the lifetime risk of developing a vertebral fracture varies among women, relatively little is known about the genetic basis of this variability. We conducted a case-control association study to test whether association of increased vertebral fractures correlated with certain alleles of the Interleukin1A (IL1A), Interleukin1B (IL1B), or Interleukin1RN (IL1RN) genes. 2527 Caucasian women (>65 years) from the SOF epidemiologic collection were selected. Cases were defined by the presence of either prevalent vertebral fracture assessed at baseline or an incident fracture after an average of 3.7 years of follow-up. Controls were randomly selected by the absence of either prevalent or incident vertebral fracture. The associations between SNP genotype and vertebral fracture in women who never used estrogen were determined using chi-square test. The logistic regression models were used to adjust for other non-genetic risk factors, such as age and BMI. Polymorphisms within the IL1B (rs16944), IL1A (rs17561), and IL1RN (rs419598) genes were strongly associated [OR ranging from 1.39 to 4.64] for incidence and/or prevalence of vertebral fracture, adjusting for age and BMI. Incidence of vertebral fracture with and without baseline fractures showed association with different sets of polymorphisms. These genetic biomarkers would have clinical utility in identifying individuals at high risk so that preventative therapies can be administered before the occurrence of vertebral fracture. A summary of the findings from the study is presented in the tables below.
Identifying risk factors for predisposition of osteoporosis (OP) is important for predicting, managing, and also in the development of therapeutics for the disease. OP is characterized by bone loss, disruption of bone micro-architecture, and increased risk for fracture. Inflammation is thought to be a key regulator of OP, since in mouse models blocking the interleukin-1 (IL1) inflammatory pathway abolishes ovariectomy-induced bone loss. Functional SNPs can alter the level and/or activity of the gene product and the biological processes that the gene product controls; this has been demonstrated for IL1 gene family. To identify genetic risk factors for OP, association between OP and polymorphisms of IL1 and other inflammatory mediators genes were examined in 2 cross-sectional studies in Asian women. These studies included one that measured bone biomarkers levels in 400 Japanese women within 36 months post menopause (see example 5 below) and another case-control study that analyzed vertebral fracture and bone biomarkers in 838 Korean women between the ages of 60-84 (current example). Variants of the IL1A, IL1B, IL1RN, or IL10 genes were associated with clinical phenotypes of OP, such as low bone mineral density (T allele/IL1RN rs315952; p=0.01), biomarkers for high bone turn over and vertebral fracture. High serum CTX and NTX levels were associated with the IL1A (T allele/IL1A rs17561; p=0.046) and the IL1B (T allele/IL1B rs4848306; p value 0.002-0.035) genes. Increased risk of vertebral fracture was associated with the IL-10 gene (C allele/IL10 rs1800872, OR=1.8, p=0.013). Interestingly, the genetic markers for OP identified between Asian and Caucasian women are in different inflammatory genes. A variant of IL1B gene (T allele of IL1B rs16944) was associated with increased risk for vertebral fracture in a previous study of 1473 Caucasian women (OR=1.56, p=0.013), whereas in this study of Asian women polymorphisms within the IL10 gene were associated. In summary, we have identified genetic risk factors for OP in Asian women and demonstrated that there are differences in the markers for OP between Caucasians and Asians.
The objective of the study set forth in this example was to test the hypothesis that in postmenopausal Korean women, age 60-84 years, not on hormone replacement therapy (HRT), common variations in interleukin-1 (IL1) genes, either individually or in composite genotype patterns: 1) are associated with risk for vertebral fracture; 2) are associated with low bone mineral density (BMD) and/or elevated markers of bone metabolism; and 3) combined with lipid factors interact in predicting the occurrence risk for vertebral fracture, low BMD and/or elevated markers of bone metabolism.
Our results show an association between the IL10 −592 CC genotype and increased risk of vertebral fracture in postmenopausal women not on HRT. Moreover, carriage of the combined CC/GT genotype of IL10 −592A>C and IL1A 4845G>T SNPs or the combined CC/AG+GG of IL10 −592A>C and IL1B 3877A>G SNPs is associated with an increased risk of vertebral fracture and a tendency to be increased concentration of plasma lipoprotein (a) [Lp (a)] in postmenopausal women without vertebral fracture.
419 postmenopausal women with vertebral fracture (cases) and 419 age-matched postmenopausal women without vertebral fracture (controls) were genotyped for polymorphisms in IL6 (−572C>G), IL1A (+4845G>T), IL1B (+3954C>T, +3877A>G, −31C>T, −511T>C, −1464G>C, −3737C>T), IL1RN (+2018T>C, +130C>T, +1444G>A), ESR1 (rs2234693T>C) and IL10 (−592A>C, −819T>C). We calculated odds ratio (OR) for vertebral fracture risk and measured bone mineral density (BMD), bone metabolism markers [carboxy-terminal propeptide of human type I procollagen (PICP), carboxy-terminal C-telopeptide of type I collagen (CTX)], serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and lipoprotein (a) [Lp (a)].
This study included 419 cases with vertebral fracture and 419 age-matched controls without vertebral fracture, who were postmenopausal Korean women, age 60-84 years, not on hormone replacement therapy. Study population was recruited from National Health Insurance Corporation Ilsan Hospital, Goyang, Korea and two sites (Gangseo and Gangnam) of Mizmedi Women's Hospital, Seoul, Korea between August 2006 and December 2007.
Inclusion criteria was generally healthy women aged 60-84 with ambulatory and community living. Vertebral fracture was determined by Lateral radiographs of the thoracic and lumbar spine as interpreted by radiographic morphometry using Genant's semiquantitative method.9 Exclusion criteria included: 1) history of comorbidities known to affect bone metabolism such as cancer, inflammatory bowel disease, pituitary diseases, hyperthyroidism, primary hyperparathyroidism, renal failure, rheumatic disease or adrenal disease; 2) use of glucocorticoids over the last 5 years; 3) A history of HRT, bisphosphonates or selective estrogen receptor modulator (SERM) use for greater than three months, or any use within the previous twelve months; 4) in cases, known accidental trauma associated with diagnosis of vertebral fracture. Study procedures were carefully followed as indicated in the Interleukin Genetics Protocol ILI06-102-OPKG.
Before participation, the purpose of the study was carefully explained to all participants and their informed consent was obtained. The study protocol complied with the Guidelines for Genome/Genetic Research issued by the Korean government and was approved by the Institute of Review Board of Yonsei University, Seoul, Korea.
All subjects completed a standardized questionnaire with a specially trained interviewer to provide information on lifestyle factors, current medication use, and medical history. Briefly, subjects were categorized into current, ex-smokers, and never smokers, and current, ex-drinkers or non-drinkers. Data on the frequency of medication use was collected for the categories of antihypertensive, hypoglycemic, antidyslipidemic, antiplatelet, and others. Also, the information of family history of osteoporosis and non-traumatic fractures was collected.
Body weight and height were measured unclothed and without shoes in the morning. Body mass index (BMI) was calculated as body weight in kilograms divided by height in square meters (kg/m2). Blood pressure was obtained from the left arm of seated patients with an automatic blood pressure monitor (TM-2654, A&D, Tokyo, Japan) after 20 min of rest. Venous blood specimens were collected in EDTA-treated and plain tubes after an overnight fast and were stored at −70° C. until analysis.
Using the TaqMan fluorogenic 5′ nuclease assay (Applied Biosystems, Foster City, Calif., USA), we genotyped ten IL1 SNPs: one IL1A SNP (+4845G>T), six IL1B SNPs (+3954C>T, +3877A>G, −31C>T, −511T>C, −1464G>C, −3737C>T), and three IL1RN SNPs (+2018T>C, +130C>T, +1444G>A), one IL6 SNP (−572C>G), one ESR1 SNP (rs2234693T>C), and two IL10 SNPs (−592A>C, −819T>C). The information of examined SNPs was shown in Table 4-1. The final volume of the polymerase chain reaction (PCR) was 5 ul, containing 10 ng genomic DNA and 2.5 ul TaqMan Universal PCR Master Mix, with 0.13 ul 40× Assay Mix. Thermal cycle conditions were as follows: 50° C. for 2 min to activate uracil N-glycosylase and to prevent carry-over contamination and 95° C. for 10 min to activate the DNA polymerase, followed by 45 cycles of 95° C. for 15 s and 60° C. for 1 min. All reactions were performed using 384-well plates and a Dual 384-Well GeneAmp PCR System 9700 (ABI, Foster City, Calif., USA) and the endpoint fluorescent readings were obtained on an ABI PRISM 7900 HT Sequence Detection System (ABI, Foster City, Calif., USA). Duplicate samples and negative controls were included to ensure accuracy of genotyping.
Bone mineral density determined at lumbar spine (L2-L4) will be assessed using Dual Energy X-ray Absortiometry (DEXA). The scanners used in study hospitals are Lunar (Madison, Wis., USA) and Norland (Trumbulll, Conn., USA). The results recorded are Z score, T score and g/cm2.
Blood fasting serum concentrations of total cholesterol and triglycerides were measured using an enzymatic method and commercially available kits on a Hitachi 7150 Autoanalyzer (Hitachi Ltd. Tokyo, Japan). After precipitation of serum chylomicron, low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) using dextran sulfate magnesium, the remaining high-density lipoprotein (HDL) cholesterol from the supernatant was measured by an enzymatic method. LDL cholesterol was indirectly estimated in subjects with serum triglyceride concentrations <400 mg/dl using the Friedewald formula.
Serum collagen type I cross-linked C-telopeptide (CTx) concentration was measured using an Electrochemiluninescence immunoassay (β-CrossLaps/serum, Roche, Germany). This assay was measured by Modular Analytics (E-170) (Roche, Germany). The intra- and inter-assay coefficients of variance were 1.57% and 2.29%, respectively.
Serum procollagen type I C-terminal peptide (PICP) concentration was measured using an enzyme immunoassay (Procollagen Type I C-Peptide EIA kit Manual, TaKaRa, Japan). The amount of PICP could be quantitated by measuring the absorbance at 450 nm using a Molecular Devices V-MAX 220 VAC ELISA reader (Molecular Devices, U.S.A). The intra- and inter-assay coefficients of variance were 6.37% and 5.13%, respectively.
Plasma lipoprotein(a) concentration was analyzed using an immunoturbidimetric assay (Tina-quant Lipoprotein (a) (Latex), Roche-BM, Switzerland). Plasma lipoprotein(a) was agglutinated with latex particles coated with anti-lipoprotein(a) antibodies. The precipitate was determined turbidimetrically at 552 nm using a Cobas Integra 800 (Roche-BM, Switzerland). The intra- and inter-assay coefficients of variance were 1.50% and 3.10%, respectively.
Hardy Weinberg Equilibrium (HWE), linkage Disequilibrium (LD), and haplotype frequencies were determined by Haploview version 3.32 (http://www.broad.mit.edu/mpg/haploview/), and subject-specific haplotypes were estimated using the HapAnalyzer program (http://hap.ngri.go.kr/index_new_.html#005) based on the EM algorithm. The χ2 test was used to determine whether individual variants were in HWE at each locus.
Statistical analyses were performed with SPSS version 12.0 for Windows (Statistical Package for the Social Science, SPSS Ins., Chicago, Ill., USA). Differences in general characteristics between controls and cases were tested by independent t-test (continuous variables) or χ2 test (categorical variables). Genotype distributions and allele frequencies were compared between controls and cases by χ2 test or Fisher's exact test. The association between vertebral fracture and genotype or haplotype was calculated using the odds ratio (OR) [95% confidence intervals (CIs)] of a χ2 test and a logistic regression analysis with adjustment for age, age at menopause, BMI, alcohol consumption, and log-BMD. To compare the differences in biomarkers according to genotype or haplotype either in control subjects or cases, we performed an independent t-test, Mann-Whitney non-parameteric test, one-way ANOVA or general linear model test followed by Bonferroni method with adjustment of covariates. We initially determined whether each variable presented a normal distribution before statistical testing, and then performed logarithmic transformation on the skewed variables (triglycerides, BMD, PICP, CTx, Lipoprotein(a)). For descriptive purposes, mean values are presented using untransformed values. Results are expressed as mean±S.E. A two-tailed value of P<0.05 was considered statistically significant.
Compared with controls, postmenopausal women with vertebral fractures had significantly lower BMD (0.84±0.01 vs. 0.80±0.01; P<0.001), higher triglyceride (125±3 mg/dL vs. 134±3; P=0.025), total-cholesterol (187±2 vs. 195±2; P<0.001) and LDL-cholesterol (107±2 mg/dL vs. 115±2; P<0.001). Crude analyses indicated that the presence of the CC genotype at the IL10 −592A>C SNP was significantly associated with an increased risk of vertebral fracture [OR 1.70 (95% CI 1.06-2.72), P=0.026]. This association remained significant after adjusting for age, age at menopause, BMI, alcohol consumption and BMD [OR 1.81 (95% CI 1.12-2.91), P=0.015]. In addition, the presence of the minor allele of the IL1RN 130C>T SNP was associated with a lower risk of vertebral fracture [OR 0.67 (95% CI 0.45-0.99), P=0.042], after adjusting for age, age at menopause, BMI, alcohol consumption and BMD [OR: 0.63, (95% CI 0.42-0.93), P=0.022]. Since only IL10 −592A>C showed an association with the increase of vertebral fracture, to determine whether the IL10 −592A>C and other SNPs exert an additive or synergistic effect on vertebral fracture, we examined the association between the combined genotype and vertebral fracture. The presence of the combined CC/GT genotype of IL10 −592A>C and IL1A 4845G>T SNPs showed an association with an increased risk of vertebral fracture [OR 3.83 (95% CI 1.07-13.7), P=0.040] after adjusting for age, age at menopause, BMI, alcohol consumption and BMD. The presence of the combined CC/AG+GG of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G) also showed an association with an increased risk of vertebral fracture [OR 1.86 (95% CI 1.06-3.27), P=0.030] adjusting for age, age at menopause, BMI, alcohol consumption and BMD. Controls with variant allele of the IL1A 4845G>T (n=65) showed significantly lower BMD (0.84±0.01 vs. 0.81±0.02; P=0.038) than those with GG (n=354). Controls with variant allele of the IL1B 3954C>T (n=30) also showed significantly lower BMD (0.84±0.01 vs. 0.79±0.03; P=0.020) and higher LDL cholesterol (106±2 mg/dL vs. 118±5; P=0.046) than those with CC (n=389). Cases of variant allele of the IL1B 3954C>T (n=24) showed significantly higher total cholesterol (194±2 mg/dL vs. 211±8; P=0.028) and LDL cholesterol (114±2 mg/dL vs. 129±7; P=0.022) levels that those with CC (n=394). In controls, the IL1B 3877A>G polymorphism showed significant associations with triglyceride (AA: 130±6 mg/dL, AG: 129±5, GG: 153±9; P=0.007) and HDL cholesterol (AA: 53±1 mg/dL, AG: 55±1, GG: 51±1; P=0.037). Controls with the combined CC/GT genotype of the IL10 −592A>C and IL1A 4845G>T SNPs (n=3) tended to have higher Lp(a) concentration than in those with the other seven genotypes (n=415) [45.7±17.3 mg/dL (CC/GT) vs. 23.5±1.09 (other genotypes), P=0.084]. Cases with the combined CC/GT genotype of the IL10 −592A>C and IL1A 4845G>T SNPs (n=12) tended to have lower HDL cholesterol concentration than in those with the other seven genotypes (n=404) [47±2 mg/dL (CC/GT) vs. 54±1 (other genotypes), P=0.084]. In addition, controls with the combined CC/AG+GG genotype of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G, n=21) tended to have higher Lp(a) concentration than in those with the other eight genotypes (n=397) [35.9±6.85 mg/dL (CC/AG+GG) vs. 23.0±1.09 (other genotypes), P=0.083]. Cases with the combined CC/AG+GG genotype of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G, n=36) have significantly lower HDL cholesterol concentration than in those with the other eight genotypes (n=379) [50±1 mg/dL (CC/AG+GG) vs. 54±1 (other genotypes), P=0.030].
General characteristics of the 419 postmenopausal women with vertebral fracture (cases) and 419 age-matched postmenopausal women without vertebral fracture (controls) are listed in Table 4-2. Compared with controls, the fracture cases consumed less alcohol (P=0.042). There was no significant difference between two groups in cigarette smoking, blood pressure, family history of osteoporosis/non-traumatic fracture, and frequency of treatment with antihypertensive, antidyslipidemic, hypoglycemic and antiplatelet drugs.
BMD, markers of bone metabolism, serum lipid profiles and Lp(a) in postmenopausal Korean women not on hormone replacement therapy are listed in Table 4-3. Compared with controls, postmenopausal women with vertebral fractures had significantly lower BMD (0.84±0.01 vs. 0.80±0.01; P<0.001) and tended to have lower carboxy-terminal propeptide of human type I procollagen (PICP) (341±5 ng/mL vs 330±6; P=0.062). With regard to serum lipid profiles, compared with controls, postmenopausal women with vertebral fractures showed significantly higher triglyceride (125±3 mg/dL vs 134±3; P=0.025), total cholesterol (187±2 vs 195±2; P<0.001) and LDL-cholesterol (107±2 mg/dL vs 115±2; P<0.001). There was no significant difference between two groups in carboxy-terminal C-telopeptide of type I collagen (CTX), HDL-cholesterol and Lp(a).
Genotype Distribution in Postmenopausal Women with or without Vertebral Fractures
All fourteen investigated polymorphisms were in Hardy-Weinberg equilibrium in the population as a whole and in the subgroups of cases and controls (Table 4-4). The distribution of the genotypes and allelic frequencies of fourteen SNPs in controls and cases are shown in Table 4-5. The allele frequencies of the SNPs were similar to those previously reported in Korean men. Out of the fourteen SNPs tested, there was a tendency of difference in genotype frequency for IL1RN 130C>T (P=0.063), IL10 −592A>C (P=0.078) and −819T>C (P=0.083). With regards to the examined two polymorphisms of IL10 gene, IL10 −592A>C and −819T>C were found to be in almost complete linkage disequilibrium (LD) in our population (D′=1.0, R2=0.989, P<0.0001). The A allele of −592A>C and the T allele of −819T>C are linked. Thus, in the following, only the results of the −592A>C are presented. There were no significant differences in genotype and allele frequencies of IL6 −572C>G, IL1A 4845G>T, IL1B 3954C>T, 3877A>G, −31C>T, −511T>C, −1464G>C, −3737C>T, IL1RN 2018T>C, 1444G>A, and ESR1 rs2234693T>C SNPs between controls and cases.
All four promoter SNPs of the IL1B gene (−31C>T, −511T>C, −1464G>C, and −3737C>T) were significantly (P<0.005) associated with each other with respect to positive LD coefficients (D′) (R2=0.59-0.99) (
Strong positive LD was also observed for IL1RN 130C>T and IL1RN 1444G>A (D′=0.993, R2=0.688, P<0.0001). When we applied an EM algorithm to the two IL1RN SNPs at positions 130 and 1444, three haplotypes were estimated to be present with appreciable frequencies in our population with estimated frequencies of 60.9% for CG, 30.7% for TA, and 8.3% for TG (Table 4-5; nucleotides refer to alleles at 130 and 1444, respectively). The estimated frequencies for the most common haplotype IL1RN 130C/1444G showed no significant difference between patients and controls (61.6% vs. 60.2%, P=0.540). Similarly, there was no significant difference between patients and controls for the estimated frequencies for the haplotype IL1RN 130T/1444A (Table 4-7).
Association of SNPs with Vertebral Fracture
Crude analyses indicated that the presence of the CC genotype at the IL10 −592A>C SNP was significantly associated with an increased risk of vertebral fracture [OR 1.70 (95% CI 1.06-2.72), P=0.026] (Table 4-6). This association remained significant after adjusting for age, age at menopause, BMI, alcohol consumption and BMD [OR 1.81 (95% CI 1.12-2.91), P=0.015]. In addition, the presence of the minor allele of the IL1RN 130C>T SNP was associated with a lower risk of vertebral fracture [Odds Ratio (OR): 0.67, (95% CI 0.45-0.99), P=0.042], after an adjustment for age at menopause, BMI, alcohol consumption and BMD [OR: 0.63, (95% CI 0.42-0.93), P=0.022] (Table 4-5). However, no significant associations were found in other polymorphisms and haplotypes of the IL6, IL1A, IL1B, IL1RN, and ESR1 genes (Table 4-6).
Since only IL10 −592A>C showed an association with the increase of vertebral fracture, to determine whether the IL10 −592A>C and other SNPs exert an additive or synergistic effect on vertebral fracture, we examined the association between the combined genotype and vertebral fracture. With regard to the IL10 −592A>C and IL1A 4845G>T SNPs, for controls the distribution of combined genotypes of the IL10 −592A>C and IL1A 4845G>T SNPs was as follows: AA/GG 41.6%, AA/GT 6.2%, AA/TT 0.2%, AC/GG 36.4%, AC/GT 7.7%, AC/TT 0.5%, CC/GG 6.7%, and CC/GT 0.7%. For cases the distribution of combined genotypes was as follows: AA/GG 37.3%, AA/GT 7.0%, AA/TT 0.2%, AC/GG 37.3%, AC/GT 6.0%, AC/TT 0.2%, CC/GG 9.1%, and CC/GT 2.9%. The presence of the combined CC/GT genotype of IL10 −592A>C and IL1A 4845G>T SNPs showed an association with an increased risk of vertebral fracture [OR 4.11 (95% CI 1.15-14.67), P=0.019] (Table 4-8). This association remained significant after adjusting for age, age at menopause, BMI, alcohol consumption, and BMD [OR 3.83 (95% CI 1.07-13.7), P=0.040].
With regard to the IL10 −592A>C and IL1B 3877A>G SNPs, for controls the distribution of combined genotypes was as follows: AA/AA 17.5%, AA/AG 20.8%, AA/GG 9.8%, AC/AA 16.0%, AC/AG 21.8%, AC/GG 6.7%, CC/AA 2.4%, CC/AG 4.1%, and CC/GG 1.0%. For cases the distribution of combined genotypes was as follows: AA/GG 14.2%, AC/GG 20.0%, AA/GG 10.1%, AC/AA 15.2%, AC/AG 21.4%, AC/GG 7.0%, CC/AA 3.4%, CC/AG 7.7%, and CC/GG 1.0%. The presence of the combined CC/AG+GG of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G) showed an association with an increased risk of vertebral fracture [OR 1.80 (95% CI 1.03-3.13), P=0.037] (Table 4-8). This association remained significant after adjusting for age, age at menopause, BMI, alcohol consumption, and BMD [OR 1.86 (95% CI 1.06-3.27), P=0.030].
Genotypic Association with BMD, Bone Markers, Serum Lipid Profiles and Lp(a)
With respect to the IL6 −572G>C polymorphism, no significant differences in the mean age at menopause, BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp (a) were observed among genotypes in either controls (postmenopausal women without vertebral fracture) or cases (postmenopausal women with vertebral fracture) (Table 4-9).
With respect to the IL1A 4845G>T polymorphism, controls of variant allele (GT or TT at IL1A 4845G>T; n=65) showed significantly lower BMD (0.84±0.01 vs. 0.81±0.02; P=0.038) and a tendency to have younger age at menopause (50.1±0.24 yr vs. 49.1±0.61; P=0.092), higher CTx (0.44±0.01 ng/mL vs. 0.49±0.03; P=0.086) and triglyceride (122±3 mg/dL vs 143±11; P=0.075) levels than those with GG (n=354). Cases of variant allele (n=68) showed younger age at menopause (49.9±0.24 yr vs. 49.0±0.62; P=0.169) and higher Lp (a) (25.1±1.34 mg/dL vs 29.0±3.19; P=0.179) than those with GG (n=349) but they did not reach the statistical significance (Table 4-10).
With respect to the IL1B 3954C>T polymorphism, controls of variant allele (CT or TT at IL1B 3954C>T; n=30) showed significantly lower BMD (0.84±0.01 vs. 0.79±0.03; P=0.020) and higher LDL cholesterol (106±2 mg/dL vs. 118±5; P=0.046) and a tendency to be higher CTx (0.44±0.01 ng/mL vs. 0.53±0.04; P=0.055) than those with CC (n=389). Cases of variant allele (n=24) showed significantly higher total cholesterol (194±2 mg/dL vs 211±8; P=0.028) and LDL cholesterol (114±2 mg/dL vs. 129±7; P=0.022) levels that those with CC (n=394) (Table 4-11).
With respect to the IL1B 3877A>G polymorphism, cases of homozygous variant allele (GG at IL1B 3877A>G) showed significantly higher triglyceride (AA: 130±6 mg/dL, AG: 129±5, GG: 153±9; P=0.007) and lower HDL cholesterol (AA: 53±1 mg/dL, AG: 55±1, GG: 51±1; P=0.037) than those with wild-type allele (AA or AG). Cases of GG genotype showed higher total cholesterol (AA: 191±3 mg/dL, AG: 195±3, GG: 201±4; P=0.162) and LDL cholesterol (AA: 112±3 mg/dL, AG: 114±2, GG: 121±4; P=0.125) but they did not reach the statistical significance (Table 4-12).
In either controls (postmenopausal women without vertebral fracture) or cases (postmenopausal women with vertebral fracture), four IL1B promoter polymorphisms (IL1B −31C>T, −511T>C, −1464G>C, and −3737C>G) showed no significant associations with the mean age at menopause, BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp (a) (−31C>T: Table 4-13, −511T>C: Table 4-14, −1464G>C: Table 4-15, and −3737C>G: Table 4-16).
In either controls (postmenopausal women without vertebral fracture) or cases (postmenopausal women with vertebral fracture), three IL1RN polymorphisms (IL1RN 2018C>T, 130C>T, and 1444G>A) showed no significant associations with the mean age at menopause, BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp (a) (2018C>T: Table 4-17, 130C>T: Table 4-18, and 1444G>A: Table 4-19).
With respect to the ESR1 intron1 T>C polymorphism, no significant differences in the mean age at menopause, BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp (a) were observed among genotypes in either controls (postmenopausal women without vertebral fracture) or cases (postmenopausal women with vertebral fracture) (Table 4-20).
In control subjects, IL10 −592A>C SNP showed a significant association with age at menopause (AA: 49.6±0.34 yr, AC: 50.0±0.32, CC: 51.7±0.60; P=0.049). However, there were no significant differences in BMD, bone metabolism markers (PICP, CTX), serum lipid profiles before and after adjustment for age at menopause. In cases, IL10 −592A>C SNP showed a tendency of association with lower HDL-cholesterol (AA: 55±1 mg/dL, AC: 54±1, CC: 50±2; P=0.092) and cases with CC genotype showed lower mean concentration of HDL-cholesterol compared to carriers with −592A variant (AA+AC: 54.3±0.7 mg/dL, CC: 50.2±1.6, P=0.041) (Table 4-21).
Combined Genotypic Association with BMD, Bone Markers, Serum Lipid Profiles and Lp(a)
To determine whether the IL10 −592A>C and IL1A 4845G>T SNPs exert an additive or synergistic effect on BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp(a), we examined the association between the combined genotype and BMD, bone markers, serum lipid profiles and Lp(a) (Table 4-22). Controls with the combined CC/GT genotype of the IL10 −592A>C and IL1A 4845G>T SNPs (n=3) tended to have higher Lp(a) concentration than in those with the other seven genotypes (n=415) [45.7±17.3 mg/dL (CC/GT) vs. 23.5±1.09 (other genotypes), P=0.084]. Cases with the combined CC/GT genotype of the IL10 −592A>C and IL1A 4845G>T SNPs (n=12) tended to have lower HDL cholesterol concentration than in those with the other seven genotypes (n=404) [47±2 mg/dL (CC/GT) vs. 54±1 (other genotypes), P=0.084] (Table 4-22).
To determine whether the IL10 −592A>C and IL1B 3877A>G SNPs exert an additive or synergistic effect on BMD, bone metabolism markers (PICP, CTX), serum lipid profiles (triglyceride, total-, HDL- and LDL-cholesterol) and Lp (a), we examined the association between the combined genotype and BMD, bone markers, serum lipid profiles and Lp(a) (Table 4-23). Controls with the combined CC/AG+GG genotype of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G, n=21) tended to have higher Lp(a) concentration than in those with the other eight genotypes (n=397) [35.9±6.85 mg/dL (CC/AG+GG) vs 23.0±1.09 (other genotypes), P=0.083]. Cases with the combined CC/AG+GG genotype of IL10 −592A>C and IL1B 3877A>G SNPs (CC at IL10 −592A>C, or AG or GG at IL1B 3877A>G, n=36) have significantly lower HDL cholesterol concentration than in those with the other eight genotypes (n=379) [50±1 mg/dL (CC/AG+GG) vs. 54±1 (other genotypes), P=0.030] (Table 4-23).
The table below shows the frequencies of risk or protective alleles in Korean OP study.
Our results show an association between the IL10 −592CC genotype and increased risk of vertebral fracture in postmenopausal women not an HRT. Moreover, carriage of the combined CC/GT genotype of IL10 −592A>C and IL1A 4845G>T SNPs or the combined CC/AG+GG of IL10 −592A>C and IL1B 3877A>G SNPs is associated with an increased risk of vertebral fracture and a tendency to be increased concentration of Lp (a) in postmenopausal women without vertebral fracture.
1FH of osteoporosis, n (%)
1FH of non-traumatic
log-transformed.
1 Family history Tested by independent t-test
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
log-transformed.
1Bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
†Confidence interval
aAdjusted for age, age at menopause, BMI, drinking status, and log-BMD
†confidence interval
aAdjusted for age, age at menopause, BMI, drinking status, and log-BMD
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
Tested by log-transformed.
1Bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide.
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
Tested by log-transformed.
1Bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide.
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
Tested by log-transformed.
1Bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide.
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP
3CTx
1BMD
2PICP
3CTx
Tested by log-transformed.
1Bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP
3CTx
1BMD
2PICP
3CTx
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
aP = 0.100 and
bP = 0.082 after adjustments for age at menopause in cotrols
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide
1BMD
2PICP (ng/mL)
3CTx (ng/mL)
tested by log-transformed.
1bone mineral density,
2Progollagen Type I C-Terminal Peptide,
3Collagen type I cross-linked C-telopeptide.
Genetic variations in the inflammation regulating genes (IL-1, IL-6 and IL-10) have been associated previously with altered baseline and stimulated expression of the inflammation cytokines, potent molecules that play a key role in osteoclast activation and hence the development of osteoporosis. The linkage of inflammation biology to osteoporosis is strengthened both by over-expression and receptor knockout animal models that result in increased bone loss or decreased bone loss respectively.1,2 Inflammation gene association studies involving cohorts from sites in the U.S., Europe and Asia have produced variable results linking individual inflammation gene polymorphisms single nucleotide polymorphisms (SNPs) with clinical outcomes relevant to osteoporosis including bone mineral density, rate of bone loss and risk of vertebral fracture.3-6 For example, Interleukin Genetics, Inc. (ILI) has data from preliminary studies (unpublished data from ILI and the Study of Osteoporotic Fractures) that indicate common SNPs in genes of the inflammation-related IL-1 cluster are associated with increased risk of vertebral fractures but not bone mineral density in postmenopausal Caucasian women free of hormone replacement therapy.
Increased bone turnover and degradation is linked to the risk for osteoporosis in postmenopausal women. Determining the mechanism by which inflammation variation may predispose to osteoporosis and vertebral fracture remains a priority for ILI. Estrogen suppresses inflammation activity, and hence the estrogen withdrawal seen in menopause should be associated with an increase in inflammatory activity. It has been established that the rate of bone turnover and bone loss is most significant during the early years after menopause. We hypothesize that it is during this period that postmenopausal Japanese women carrying inflammation genotypes will demonstrate a significant increase in bone turnover and degradation that, if untreated, may add to their risk for osteoporosis and vertebral fracture.
Study objective. This study was performed to test the hypothesis that specific inflammation genetic patterns of inflammation and bone metabolism genes are associated with an increase both in bone turnover and in the amount of bone degradation in Japanese women in early menopause, as measured by serum levels of bone biomarkers Osteocalcin (OC), Collagen Type I Cross-linked C-telopeptide (CTx), and Collagen Type I Cross-linked N-telopeptide (NTx). A further objective was to test if increases in serum bone biomarkers OC, CTx, and NTx associated with inflammation genetic patterns in early menopause are inversely related to MSM. Regression lines for bone biomarkers levels plotted against MSM were plotted and compared for genotype positive and genotype negative individuals. A cross-sectional study design with a quantitative BMD/BMI/biomarker component was used. Non-parametric analysis (Mann-Whitney test) was used to determine differences between levels of bone turnover markers according to inflammation genotype. Regression analysis adjusted for bone mineral density (BMD), months since menopause (MSM), age and body mass index (BMI).
A cohort of Japanese women, ≦60 years of age, who were generally in good health and had reached early post-menopause (at least 6 months and no more than three and one-half (3.5) years since their last menstrual period), not on hormone replacement therapy nor any medication for osteoporosis, were considered for this study. Four hundred (400) Japanese women were entered into this study. In order to be included in the study, the Japanese women 60 years of age gave written informed consent of their own free will; they were at least ≦6 months from their last menstrual period and no more than 3.5 years postmenopausal. They were generally healthy, ambulatory and community living. After at least an eight (8) hour fast, demographic information and anthropometric parameters were collected; there was a singe blood draw for biomarker analysis, a cheek swab for DNA genetic testing and a DEXA scan for BMD. All procedures were completed in one or two visits and subjects were then dismissed from the study. Females with a history of comorbidities known to affect bone metabolism such as cancer, inflammatory bowel disease, pituitary diseases, hyperthyroidism, primary hyperparathyroidism, renal failure, rheumatic disease, adrenal disease or Paget's disease were excluded form the study. Also, females with a history of hormone replacement therapy (HRT) or selective estrogen receptor modulator (SERM) use, or other medications or supplements, i.e., bisphosphonates, calcitonin, PTH, Vitamin K2 (menatetrenone), Active Vitamin D, oral steroids or metheltrexate, or a history of fracture within the previous 2 years were excluded from enrollment in this study. All subjects entered into the study were analyzed.
Data collection requirements are as follows.
Demographics: Current age, age at menopause, smoking status, height, weight, current medications; Family history of osteoporosis? (Y/N); and Family history of non-traumatic fractures? (Y/N).
Clinical Endpoints: Bone mineral density (BMD) determined at lumbar spine (L2-L4) was assessed using Dual Energy X-ray Absortiometry (DEXA). The results recorded are Z score, T score and g/cm2. Weight and height were recorded to determine Body Mass Index (BMI) which is calculated as weight in kilograms/height2 in meters.
Biochemical Markers Nine mL of blood was collected by venipuncture according to the standard procedure for blood sampling, for the following biochemical markers: Serum OC, Serum CTx, and Serum NTx.
Source of DNA: The DNA was obtained from cell samples from the inside of the subject's mouth. Following the instructions in the Protocol, Appendix B, a sterile swab was used to collect cells from the inside of the cheek. The swab packets were sent to Interleukin Genetics, Inc, Waltham Mass. genotyping laboratory. Samples will be provided to ILI coded and blinded in such a way that they cannot be linked to the subject's personal information.
Genotyping: Genotyping was carried out by a genetics genotyping facility, Interleukin Genetics, Inc, Waltham Mass. The swab packets were stored until there were 100 sets, or they had been stored one month, they were shipped to Interleukin Genetics, Inc. for processing. Approximately 5% of the cohort had blind duplicate swabs sent for quality control. DNA samples were evaluated for a number of polymorphisms and may include the following:
To test the hypothesis that specific inflammation genetic patterns are associated with an increase both in bone turnover and in the amount of bone degradation in Japanese women in early menopause, as measured by serum levels of bone biomarkers OC, CTx, and NTx, ANOVA analysis was used to determine differences between levels of bone turnover markers according to inflammation genotype. Regression analysis adjusted for BMD, MSM, age and BMI. To test if the increase in serum bone biomarkers OC, CTx, and NTx associated with inflammation genetic patterns in early menopause are inversely related to months post menopause, regression lines for bone biomarkers levels plotted against MSM were plotted and compared for genotype positive and genotype negative individuals. This study was powered based on the results from analysis of the Caucasian biomarker study adjusted for the frequency of the predicted inflammation risk genotype.
Baseline demographic and background characteristics—Descriptive statistics. Test for collinearity: model with outcome=current age, months since menopause, BMI, Z-score and T-score. Severe collinearity between age, Z-score and tscore (variance inflation factors>>10; correlation coefficients>0.95). Removed T-score from the model (T-score was missing on n=37 subjects; no subjects were missing age or Z-score). Final model with T-score removed showed no further evidence of collinearity.
Genotype Quality Control. Data on 15 polymorphisms was received. Ten subjects had repeat measures of all SNPs. There was complete concordance between each replicate (the exception was one SNP where the genotype was indeterminant in one replicate). Duplicates were removed. In addition, subjects numbered from 501-507 were removed as they weren't in the phenotype dataset (assume these were additional QC subjects?).
Genotype data were recoded and run in HAPLOVIEW software to obtain minor allele frequencies, percent missing and Hardy-Weinberg Equilibrium (HWE) (summarized below). One SNP, ESR(PvuII), failed HWE (p<0.002) and also had the lowest call rate of any of the SNPs (96%). This SNP should be evaluated more closely to rule out genotyping errors. All other SNPs passed QC. Minor allele frequencies ranged from 0.04 to 0.49.
The table below shows the frequencies of risk or protective alleles in Japanese OP study.
Linkage disequilibrium (LD) plot. Linkage disequilibrium (LD) plot were generated in Haploview software (r2 shown) for all SNPs. Only modest LD was detected between the two ESR1 SNPs; strong LD between the two SNPs in IL10; moderate to strong LD across the IL1B 5′ region and moderate LD between two of three IL1RN SNPs. See
Phenotype Quality Control. Diagnostics for linear regression of three continuous outcomes of serum Collagen Type 1 Cross-linked N-telopeptide (NTX), Collagen Type 1 Cross-linked C-telopeptide (CTX) and Osteocalcin (OC) were performed.
1. Test for outliers and normality of each trait:
a. NTX—non-normal (Shapiro Wilks p<0.0001). Log transform. Test NTX in model with covariates (non-genetic). Plot residuals. Two values were considered outliers (residuals>+2) and removed. Final log-transformed NTX in remaining n=398 was normally distributed, as were the residuals. No heteroscedasticity.
b. CTX—non-normal (Shapiro Wilks p<0.0001). Log transform. Test CTX in model with covariates (non-genetic). Plot residuals. Non-normal. Remove lowest two (residuals<−1.4) measures of CTX (both of these CTX levels were originally coded as <1.0, but had been left as 1.0 for analysis). Final log-transformed CTX in remaining n=398 was normally distributed, as were the residuals. No heteroscedasticity.
c. OC—non-normal (Shapiro Wilks p<0.0001). Log transform. Test OC in model with covariates (non-genetic). Plot residuals. Normal. No heteroscedasticity. No exclusions. Final n=400.
2. Test for collinearity: model with outcome=current age, months since menopause, BMI, Zscore and Tscore. Severe collinearity between age, zscore and tscore (variance inflation factors>>10; correlation coefficients>0.95). Removed Tscore from the model (Tscore was missing on n=37 subjects anyway; no subjects missing age or Zscore). Final model with Tscore removed showed no further evidence of collinearity.
Association analysis. Each SNP was run in three different linear regression models for each outcome (NTX, CTX, OC). Prior to analysis, all three outcome variables were log-transformed and outliers eliminated as described above. The three models that we ran for each outcome included: 1) SNP in additive model, unadjusted—SNP alone; 2) SNP in additive model, adjusted for current age, months since menopause (MSM), body mass index (BMI) and Z-score; 3) SNP in additive model, adjusted for everything in second model plus an interaction term between genotype and MSM. P values for these associations are shown in the table below and the accompanying graphs. Highlighted SNPs are for p<0.05 for first two models and p<0.10 for third model (threshold for detecting interaction is typically set to this level for epidemiological studies).
Conclusions/Observations. There was consistent interaction between MSM and SNPs IL1A (+4845) and IL1B (+3877) across all three traits; ESR1(PvuII) interaction across two traits (note: this SNP was not in HWE); and consistent associations with all three traits across the 5′ region of the IL1B gene. In all cases, controlling for covariates results in a modest improvement in association. See
Analysis of IL1B promoter haplotypes (diplotypes). The table below shows haplotype frequencies of four SNPs in the 5′ region of IL1B (positions −3737, −1464, −511, −31), which all showed associations with bone traits, were determined using Chaplin software.
To test whether haplotypes may be better determinants of bone outcomes than individual SNPs, we looked at pairwise interaction between SNPs in a regression model. P values for interaction between SNPs in the full regression model are shown below:
There was modest evidence of interaction for most SNP pairs, indicating that haplotypes are important. LD between −511 and −31 was very strong, making the analysis of both redundant. Therefore, diplotypes were determined from combinations of genotypes of IL1B −511, −3737 and −1468. Only common diplotypes (freq>1%) were included (above line). There was a significant association between 7-level (first 7 listed) IL1B diplotype and CTX (p=0.05).
There were no subjects with group B significant association with BHAP variable (p=0.03)
Each haplotype (BP1, BP2, BP3, BP4) was recoded into a separate variable with levels of 0, 1 or 2, corresponding to the number of variant (minor) alleles present. When analyzed this way for log CTX, the BP1 haplotype was significantly associated with CTX (p=0.003), as was the BP2 haplotype (p=0.04), but not BP3 (p=0.64) or BP4 (p=0.20). The graph of association between number of BP1 haplotypes and log CTX is shown in
Next, we asked whether the BP1 haplotype was in LD with any other SNPs in our study. BP1 haplotype was in LD with other ILB SNPs. When individual SNPs were added to a model with BP1 haplotype. IL1A +4845 became a significant independent predictor of CTX (p=0.04). This is similar to our finding when we conditioned on the 8-level IL1B promoter diplotype variable or just on IL1B −3737 (See
Model building. We next sought to determine if any other associations would be uncovered if we conditioned on the IL1B promoter region. We conditioned on either diplotype (8 level variable), IL1B−3737, IL1B−1468 or IL1B−511.
Including other SNPs into the model one at a time with one of these variables, we uncovered a significant association with one other SNP, IL1A+4845. In a model conditioning on diplotype, both diplotype and IL1A+4845 associations become more pronounced. Similarly, in a model conditioning on either BP1 or IL1B−3737, both of these SNP and IL1A+4845 were significantly independently associated with log CTX.
Next, we created a variable that simply counted the number of risk alleles at these two loci (0, 1, 2 or 3) and found a significant association with CTX (p=0.0003) that explained 3.3% of the variance. See
Genotype interactions with months since menopause (MSM). Two SNPs showed consistent significant interactions with MSM for the different bone traits: IL1A (+4845) and IL1B (+3877). See
Additivity Model Assumptions. The model used in all analyses was an additive one. Additional models (general, dominant, recessive) were tested, but in most cases, the additive model gave the best (most significant) results. Indeed, for IL1B, the graph in
The p values shown for model 3 are specifically testing whether there is interaction between the SNP and MSM. For the IL1B SNPs, there is no evidence of interaction, which is interpreted to mean that the association between the SNP and bone marker is constant across levels of MSM. In this case, you would remove the interaction term from the model and just go with the p value for model 2. For the IL-1A SNP, there is no association in model 2 because the interaction between the SNP and MSM is obscuring an association. In other words, the effect of the SNP on bone markers is very different for women with fewer MSM versus those with more MSM. The IL1A (+4845) graph for OC (
Independent Association of IL1 gene cluster SNPs or haplotypes and bone turnover makers:
The BP1 and BP2 haplotype were significantly associated with increased level of CTX;
In a model conditioning on diplotype, IL1B promoter diplotype and IL1A+4845 associations become more pronounced;
Similarly, in a model conditioning on either BP1 or IL1B−3737, both of these markers and IL1A+4845 were significantly independently associated with log CTX. There was no evidence of interaction between these loci;
When the carriage of both risk alleles (IL1B −3737 T and IL1A +4845 T) were considered, i.e., when we counted the number of risk alleles at these two loci (0, 1, 2 or 3) a significant association with CTX (p=0.0003) was found that explained 3.3% of the variance; and
With increasing numbers of risk alleles at these 2 loci, there was an increasing gradient of the CTX level (
Association of IL1A4845+ (Allele T) and Increased Level of Bone Biomarkers and Interaction with Time Since Menopause.
The data indicate a clear association of the IL-1A4845+ (allele T) with increased levels of 2 biomarkers of bone turnover—CTx and Osteocalcin, in early months after menopause. In addition, the copy number of the T-allele is associated with increased level of these biomarkers. With 2 copies of the T-allele, the highest levels of bone turnover is observed, with 1 copy an intermediate level of bone turnover, and with 0 copies the lowest level of bone turnover occurs in the early months after menopause. With increasing time (months) since menopause, these higher biomarker levels decline in IL-1A 4845+ T/T sharply, the decline in bone turnover markers is also apparent, but more modest in individuals who are IL-1A 4845+ G/T. In contrast, IL-1A 4845+ G/G individuals, who have low levels of bone turnover in earlier months after menopause, have increasing levels of bone turnover in later months since menopause (MSM).
The same pattern of elevated bone biomarkers in early MSM and then a gradual decline over time is seen with carriers of the minor allele of the IL-1B 3877+ (G) allele. However, the slope of the decline over time is more gradual for Osteocalcin than for CTx for carriers of the minor alleles of the IL-1A 4845+ (T) SNP and the IL-1B 3877+ (G) allele. This could be related to the differences in biochemical and physiologic kinetics of these two different biomarkers of bone turnover.
It is possible that in women who have high bone turnover in the early months since menopause, there is a greater risk of fracture at an earlier age. Bone mineral density can decline during the perimenopausal stage, several years before the onset of menopause, since estrogen levels are also declining High bone resorption, as indicated by higher levels of bone resorption serum biomarkers, in the absence of adequate levels of estrogens during perimenopausal and early menopausal years could tilt the finely tuned balance of bone resorption and bone formation necessary for optimal bone strength and lead to fragile bones. Therefore, carriers of the minor alleles of IL1A+4845 and IL1B+3877 may be at greater risk for bone fracture at an earlier age.
From the foregoing detailed description of the specific embodiments of the invention, it should be apparent that unique methods have been described. Although particular embodiments have been disclosed herein in detail, this has been done by way of example for purposes of illustration only, and is not intended to be limiting with respect to the scope of the appended claims which follow. In particular, it is contemplated by the inventor that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.
While the invention has been described with reference to particularly preferred embodiments and examples, those skilled in the art recognize that various modifications may be made to the invention without departing from the spirit and scope thereof.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety.
CVD Panel Definitions:
IL-1B Promoter Haplotype Definitions:
IL-1B Haplotype Pairs:
IL-1B Haplotype Pairs:
This application claims the benefit of U.S. Ser. No. 61/145,403, filed Jan. 16, 2009 and is continuation-in-part of U.S. Ser. No. 12/142,476, filed Jun. 19, 2008, which is a continuation-in-part of U.S. Ser. No. 10/914,396, filed Aug. 9, 2004, which is a continuation-in-part of U.S. Ser. No. 10/428,333, filed May 2, 2003 which is a divisional of U.S. Ser. No. 09/650,785, filed Aug. 30, 2000 (now U.S. Pat. No. 6,558,905), which claims the benefit of priority from Provisional Application 60/151,460, filed Aug. 30, 1999. The above related applications are incorporated by reference herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 61145403 | Jan 2009 | US | |
| 60151460 | Aug 1999 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09650785 | Aug 2000 | US |
| Child | 10428333 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12142476 | Jun 2008 | US |
| Child | 12687657 | US | |
| Parent | 10914396 | Aug 2004 | US |
| Child | 12142476 | US | |
| Parent | 10428333 | May 2003 | US |
| Child | 10914396 | US |
