The present application claims the priority from Japanese Patent Application No. 2003-406750 filed on Dec. 5, 2003, the content of which is hereby incorporated by reference into this application.
The present invention relates to a method of evaluation for assisting in the diagnosis of multiple sclerosis. More particularly, the present invention relates to a method for analyzing the expression of genes associated with multiple sclerosis, a chip for analyzing the expression of multiple sclerosis-associated genes, and a gene group for determining whether or not multiple sclerosis has been developed.
Multiple sclerosis (hereafter abbreviated as “MS”) develops a variety of symptoms, such as visual motor sensory, and cognitive disturbances. This is because the “myelin” that covers the nerve fibers of the brain and the spinal cord become inflamed, and the transmission of neural information becomes insufficient. The cause of MS has not yet been elucidated, and MS is a chronic disease that cannot be completely cured by contemporary medicine. MS is regarded as an “autoimmune disease,” whereby the immune system erroneously attacks itself, although the mechanism of disease development has not yet been elucidated. At present, it is estimated that at least 5,000 patients with MS are present in Japan and that as many as about 1,000,000 MS patients are present in the world.
One feature of MS is that a majority of patients suffer from relapses many times. The severity and duration of relapse varies depending on the patient, and the rate of a patient recovering from MS becomes relatively high during remission after the acute stage. This type of MS is referred to as “relapsing-remitting MS.” Some patients suffer from increased neurological deficits MS as they experience repeated relapse. In contrast, there is another form of MS in which the disease conditions gradually progress after development of MS. This type of MS is referred to as “progressive MS.” The number of patients affected with the latter type is considered to be small in Japan.
MS is roughly classified in two categories in terms of the affected areas: conventional MS (C-MS) that extensively affects the entire central nervous system including the brain, the cerebellum, and the brain stem; and opticospinal MS (OS-MS) that relatively selectively affects the optic nerve and the spinal cord. While a majority of western Caucasians contract C-MS but rarely contract OS-MS, approximately one third of Asian patients with MS, including Japanese patients, contract OS-MS.
Up to the present, magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) examination, and other techniques have been employed as the methods for diagnosis of MS. MRI is very useful in terms of, distinguishing active lesions from inactive lesions by the use of a contrast medium (gadolinium), although not all the lesions can be detected. In the case of OS-MS where there is no substantial development of lesions in the brain or in the cerebellum, MRI testing is particularly difficult. In addition, diagnosis needs to be made by a well-trained neuroradiologist in order to evaluate the development of the disease based on images. In the case of the cerebrospinal fluid (CSF) test, the cerebrospinal fluid that flows around the brain and the spinal cord is collected, and the quantity of lymphocytes, antibodies (the immunoglobulin G; IgG), and myelin basic protein are analyzed, thereby allowing inspection regarding the presence of an inflammatory lesion. Although this technique is useful, it inflicts a great burden on the patients, because of the necessity of sticking a needle into the back of a patient. Accordingly, it has been very difficult to determine whether or not MS has been developed in a simple accurate, and less time-consuming manner by conventional testing techniques, from the viewpoint of detection sensitivity and the burdens on test subjects.
An object of the present invention is to provide a method of evaluation for assisting in the diagnosis of multiple sclerosis that provides useful information, inflicts fewer burdens on a subject, is simple, and is highly reliable.
In order to attain the above object, the present inventors have conducted concentrated studies. As a result, they have found that analysis of the expression level of a specific gene in the peripheral blood lymphocytes of the test subject enables the evaluation of whether or not MS has been developed. This has led to the completion of the present invention.
Hereafter, specific means for attaining the object are described.
The present invention relates to a method for evaluating whether or not a subject has been affected with MS by analyzing the gene expression levels of proteins associated with apoptosis inhibition or activation using messenger RNA isolated from peripheral blood lymphocytes of the subject.
The present invention also relates to a method for evaluating whether or not a subject has contracted MS by analyzing the expression level of a gene selected from among those indicated by the symbols RIPK2, NFKBIE, TNFAIP3, DAXX, TNFSF10, BAG1, TOP1, ADPRT, CREB1, MYC, BAG4, RBBP4, GZMA, BCL2, and E2F5 using messenger RNA derived from peripheral blood lymphocytes of the subject.
Also, the present invention relates to a method for evaluating whether or not a subject has contracted MS by analyzing the expression level of any of the genes, the symbols of which are shown in Table 1, using messenger RNA derived from peripheral blood lymphocytes of the subject.
Also, the present invention relates to a method for evaluating whether or not a subject has contracted MS by analyzing the expression level of any of the genes, the symbols of which are shown in Table 2, using messenger RNA derived from peripheral blood lymphocytes of the subject.
Further, the present invention relates to a method for evaluating whether or not a subject has contracted MS by isolating CD3+ T-cells from the peripheral blood lymphocytes of the subject and analyzing gene expression in the T-cells.
The present invention relates to a method for evaluating whether or not a subject has contracted MS wherein a DNA chip is used as a means for analyzing gene expression.
The present invention further relates to a DNA chip for evaluating whether or not MS has been developed, which has the aforementioned gene mounted thereon.
The present invention has been completed based on the results of studying the method for evaluating whether or not MS has been developed by analyzing the expression levels of a specific gene group in the peripheral blood lymphocytes of the subject via a simple means such as a DNA chip. The use of the method of evaluation according to the present invention enables the diagnosis of MS in a simple and accurate manner.
Multiple sclerosis (MS) is an autoimmune disease, and malfunction of the immune system is deduced to be the cause thereof. The immune system is an extremely complicated system in which an extensive signal transducing network exists among a variety of cells, centering on T-cells and B cells. Accordingly, it is very dangerous to judge abnormality in such immune system or the repaired state thereof simply by observing individual functions of T-cells producing various cytokines such as lymphotoxin, tumor necrosis factor (TNF), interferon γ (INFγ), or transforming growth factor β (TGFβ). Thus, the present inventors have developed a method for studying the conditions of the immune system by observing the functions of a wider range of gene groups.
Recently, a method for analyzing gene expression in a sample cell has drawn attention. In this method, a large number of DNA fragments having different sequences are independently immobilized on different sites on a substrate, the resultant is referred to as a “DNA chip” or “DNA array.” A reverse transcript of messenger RNA (fluorescence-labeled or radioisotope-labeled) that had been isolated from the target cell are sprinkled on the DNA chip or DNA array, hybridization is carried out, and the degree of hybridization of the reverse transcript to the site at which DNA fragments are immobilized relating to each sequence is determined, thereby analyzing the gene expression in the sample cell. The present inventors used this DNA chip technique to extensively determine the differences in the gene expression patterns in the peripheral blood lymphocytes of healthy volunteers and in those of MS patients.
This study was conducted to use lymphocytes responsible for the immune system obtained from peripheral blood as a sample. The use of peripheral blood lymphocytes is important from the viewpoint of the less invasive way on a subject. The 72MS patients who had been diagnosed as having relapsing-remitting MS based on comprehensive evaluation via MRI test, an evoked potential test, a cerebrospinal fluid test, and clinical findings, along with 22 healthy volunteers, were asked for their cooperation. The gene expression patterns in peripheral blood lymphocytes between MS and healthy volunteers were thoroughly compared. A DNA chip (DNA chip for analyzing drug responses, Hitachi Co., Ltd.) having approximately 1,260 types of human genes associated with cytokine, signal transmission, growth factor, oncogene, or apoptosis mounted thereon was used. After approximately 10 ml of blood was taken from the subjects, lymphocytes were separated using a density gradient centrifugation medium (Ficoll-Paque PLUS®, Amersham Biosciences), and the lymphocytes were divided into CD3+ T-cells and CD3− non-T-cells (monocytes, B cells, and NK cells) using the AutoMACS® magnetic cell separation system (Miltenyi). Subsequently, total RNA was extracted from the separated cell fractions using the RNeasy Mini Kit (Qiagen). The yield of total RNA derived from CD3+ T-cells was 3 to 6 μg, and that of total RNA derived from CD3− non-T-cells was 2 to 4 μg, per subject. Blood was sampled from the patients before the initiation of interferon β therapy.
Healthy volunteers (three individuals) were recruited, blood was taken, CD3+ T-cells and CD3− non-T-cells were isolated, RNA was extracted therefrom, equivalent amounts of samples obtained from three volunteers were pooled, the resulting mixture was twice subjected to RNA amplification via in vitro transcription, and the amplified RNA was designated as a reference. This reference was used as a universal reference sample among all healthy volunteers and MS patients.
Total RNA extracted from CD3+ T-cells and CD3− non-T-cells obtained from the healthy volunteer group and the patient group was subjected to RNA amplification via in vitro transcription. Thereafter, Cy5-labeled cDNA was synthesized via reverse transcription utilizing Cy5-dCTP. In contrast, the reference CD3+T-cell and CD3− non-T-cell samples derived from healthy volunteers were independently subjected to reverse transcription using Cy3-dCTP to synthesize Cy3-labeled cDNA. The cDNA of the patients and healthy volunteers was mixed with the same amount of the reference cDNA, the resultant was applied to the DNA chip, and hybridization was carried out at 62° C. for 12 hours. After the washing, the fluorescence intensity at each spot was analyzed using a scanner (ScanArray 5000, GSI-Lumonics), and the ratio of the expression level of each gene between the samples obtained from the healthy volunteer or the patient and the reference was determined. Since the gene expression levels are expressed as a relative value to a common reference sample in this experiment utilizing DNA chips, differences in each gene expression level between the healthy volunteers and the patients can be easily determined.
The method of analysis is as follows. The data of the patient group and the healthy volunteer group were subjected to T-test. The gene group that exhibited statistically significant differences in expression levels between the aforementioned two groups even after considering individual (sample-sample) differences was selected. The T-test was carried out by the Bayes' estimation reported by A. Long et al. in combination with the T-test (Journal of Biochemistry, vol. 276, pp. 19937-19944, 2001), and the acceptable false positive value was determined to be 0.05. The results attained from CD3+ T-cell samples are shown in Table 1, and the results attained from CD3− non-T-cell samples are shown in Table 2. The P values for expression ratio logarithmic values are shown in the tables. As the p value becomes smaller, the sample is determined to belong to a gene group that exhibits more significant differences in the expression level between healthy volunteers and MS patients, i.e., representing a MS-specific peripheral blood marker. All the p values for the groups of genes listed in Table 1 and in Table 2 are smaller than 1E-4, which are statistically significantly different. Thus, the gene group is determined to be reliable MS-specific peripheral blood gene signature.
Among the variable gene group shown in Table 1 or 2, the groups of genes indicated by the symbols RGS14, CHST2, NR4A2, MAPK1, SMARCA3, TPST2, ATP6D, TCF17, ARH1, HSPA1A, AGTRL2, and PTPN6 that have the p values of less than 1E-10 can be selected as the groups of genes exhibiting significant differences in expression levels. These are the most useful MS-specific peripheral blood markers.
The groups of genes indicated by the symbols CHST4, GHSR, COX15, IL18R1, AKAP11, CDC42, HSPA1L, RAB7L1, POLR2H, GRO2, PEMT, RPA1, and NFATC3 that have p values of less than 1E-5 in Table 1 and in Table 2 are also valuable as MS-specific peripheral blood markers.
The groups of genes indicated by the symbols ICAM1, CDC25B, IL1R2, CR2, CD3Z, MAD, CSF1, ARHGEF1, PRKDC, RASSF1, SCYA2, and ABCA1 that have p values of less than 1E-5 in Table 2 are also valuable as MS-specific peripheral blood markers.
Further, Table 1 and Table 2 contain a large number of groups of genes that are associated with apoptosis regulation and activation. The groups of apoptosis-associated genes indicated by the symbols RIPK2, NFKBIE, TNFAIP3, DAXX, TNFSF10, BAG1, TOP1, ADPRT, CREB1, MYC, BAG4, RBBP4, GZMA, BCL2, and E2F5 are identified as MS-specific peripheral blood markers.
According to the test comparing the healthy volunteer group and the MS patient group, the number of marker genes selected using the CD3+ T-cellsamples was approximately two times that selected using the CD3− non-T-cellsamples. This indicates that T-cells are more useful for distinguishing MS from healthy subjects patients than non-T-cells.
Subsequently, cluster analysis was carried out based on the expression level of the selected genes in order to group 66 MS patients and 17 healthy volunteers. The hierarchical clustering method was employed for this analysis. The resulting dendrograms are shown in
Thus, it was found that analysis of gene expression in peripheral blood lymphocytes of the subject with the use of a specific gene group as a marker enabled us to clearly distinguish of the healthy volunteer group from the patient group.
The method for analyzing the gene expression level employed in the present invention is not limited to one involving DNA chip technology. It is evident that quantitative PCR, Northern blotting, and other means can also be employed.
The method for analyzing data is not limited to one involving clustering. Machine learning algorithms, such as the Support Vector Machine, can also be employed.
The embodiments of the present invention are hereafter described in detail with reference to the examples.
The data concerning the gene expression of the group of patients who had been clinically proved to have contracted MS and the group of healthy volunteers were stored in a database. The results of gene expression analysis of the subjects who were to be evaluated concerning the development of MS were analyzed with reference to the aforementioned database. Thus, examples of evaluation of whether or not the subjects had contracted MS were shown.
The database containing data concerning the aforementioned 66 patients and 17 healthy volunteers was employed. A total of five subjects among which three patients had been recognized as having relapsing-remitting MS based on comprehensive evaluation via MRI test, an evoked potential test, a cerebrospinal fluid test, and clinical findings and two healthy volunteers were employed. After 10 ml of peripheral blood had been taken from each subject, the origins of the samples, i.e., whether the sample was obtained from a patient or a healthy volunteer, were kept unknown via management based only on case numbers.
After lymphocytes had been separated from each blood sample using a density gradient centrifugation medium (Ficoll-Paque PLUS®, Amersham Biosciences), the lymphocytes were divided into CD3+ T-cells and CD3− non-T-cells (monocytes, B cells, and NK cells) using the AutoMACS® magnetic cell separation system (Miltenyi). Subsequently, total RNA was extracted from the separated cell fractions using the RNeasy Mini Kit (Qiagen). The yield of total RNA derived from CD3+ T-cells was 3 to 6 μg, and that of total RNA derived from CD3− non-T-cells was 2 to 4 μg, per subject.
At the outset, an oligo (dT) 24 primer comprising a T7 promoter sequence added thereto was annealed to 2 μg of total RNA to synthesize the first strand DNA. Subsequently, this first strand DNA was used as a template to synthesize second strand DNA having a T7 promoter sequence. Finally, the second strand DNA was used as a template to synthesize RNA with the aid of T7 RNA polymerase. A random hexamer was annealed to 4 μg of the amplified RNA to conduct reverse transcription reaction, and Cy5-dCTP was incorporated into the strand to label it with fluorescence.
The control sample was prepared in the following manner. Healthy volunteers (three individuals) were recruited, 15 ml of peripheral blood was taken from each volunteer, and CD3+ T-cell-derived and CD3− non-T-cell-derived total RNAs were extracted, by the utilization of the aforementioned density gradient centrifugation, magnetic cell separation system, and RNA extraction kit. After 3 μg samples of total RNA obtained from each of three volunteers were pooled, Cy3-fluorescence labeled cDNA was synthesized via the aforementioned RNA amplification and reverse transcription, and the resultant was designated as the universal reference.
Cy5-cDNA prepared from each patient's sample was mixed with the same amount (4 μg) of Cy3-cDNA that was a universal reference, the mixture was applied to the aforementioned DNA chip (the DNA chip for analyzing drug responses, Hitachi Co., Ltd.), and hybridization was carried out at 62° C. for 12 hours. After washing, the fluorescence intensity at each spot was analyzed using a scanner (ScanArray® 5000, GSI-Lumonics), and quantification software (QuantArray, GSI-Lumonics) was used to determine the ratios of the gene expression intensity between the control sample and the subject sample.
The data for these five subjects were combined with the database comprising the data concerning the aforementioned 66 patients and 17 healthy volunteers, and hierarchical clustering analysis was carried out concerning the genes shown in Table 1 and Table 2. The results attained from CD3+ T-cell samples utilizing the gene group shown in Table 1 are shown in
These results clearly indicate that analysis of the gene expression data with the utilization of the gene group shown in Table 1 and Table 2 as gene markers enables us to distinguish MS patients from healthy volunteers. This indicates that the effectiveness on diagnosis of MS by the present invention is very high. Based on the comparison of the results attained from CD3+ T-cells and those from CD3− non-T-cells, the distinction of MS patients from healthy subjects was accurately carried out in accordance with the origins of the samples. Since CD3+ T-cell samples provide more accuratedistinction, the use of T-cells as peripheral blood lymphocytes was found to be the most valuable.
Among the groups of variable genes shown in Table 1 and in Table 2, the groups of genes indicated by the symbols RGS14, CHST2, NR4A2, MAPK1, SMARCA3, TPST2, ATP6D, TCF17, ARHI, HSPA1A, AGTRL2, and PTPN6 that have p values of less than 1E-10; the groups of genes indicated by the symbols CHST4, GHSR, COX15, IL18R1, AKAP11, CDC42, HSPA1L, RAB7L1, POLR2H, GRO2, PEMT, RPA1, and NFATC3 that have p values of less than 1E-5 in Table 1 and in Table 2; and the groups of genes indicated by the symbols ICAM1, CDC25B, IL1R2, CR2, CD3Z, MAD, CSF1, ARHGEF1, PRKDC, RASSF1, SCYA2, and ABCA1 that have p values of less than 1E-5 in Table 2 be considered as particularly useful gene markers for evaluating whether or not MS has been developed.
The groups of apoptosis-associated genes indicated by the symbols RIPK2, NFKBIE, TNFAIP3, DAXX, TNFSF10, BAG1, TOP1, ADPRT, CREB1, MYC, BAG4, RBBP4, GZMA, BCL2, and E2F5 are also particularly useful as gene markers for evaluating whether or not MS has been developed.
The groups of genes shown in Table 1 are useful as gene markers for evaluating whether or not MS has been developed in the case of T-cell-derived samples. The groups of genes shown in Table 2 are useful as gene markers for the aforementioned purpose in the case of non-T-cell-derived samples.
The thus selected groups of genes can be employed for diagnosing MS if a chip having a probe that specifically binds to the gene group immobilized on the surface thereof is prepared for at least some of those genes.
Homo sapiens regulator of G protein
Homo sapiens COX15 (yeast) homolog,
Homo sapiens serine/threonine kinase
Homo sapiens HKL1 mRNA, complete cds
Homo sapiens carbohydrate
H. sapiens IL-1R2 mRNA for type II
Homo sapiens putative tumor supressor
Homo sapiens mRNA for
Homo sapiens antagonizer of myc
Homo sapiens mRNA for small
Homo sapiens NF-AT4c mRNA, complete
Homo sapiens HSPA1L mRNA for Heat
Homo sapiens growth hormone
Homo sapiens silencer of death domains
Homo sapiens DNA-dependent protein
Homo sapiens putative tumor suppressor
Homo sapiens mRNA for ATP-binding
Homo sapiens Fas-binding protein Daxx
Homo sapiens death receptor 5 (DR5)
Homo sapiens candidate tumor suppressor
Homo sapiens heat shock 70 kD protein 1
Homo sapiens E2F transcription factor 4,
Homo sapiens mRNA for Rev-ErbAalpha
Homo sapiens GA-binding protein
Homo sapiens CDC2-related protein kinase
Homo sapiens CD3D antigen, delta
Homo sapiens
Homo sapiens angiotensin receptor-like 2
All publications, patents, and patent applications cited herein are incorporated herein by reference in their entirety.
The present invention can be utilized for diagnosis of multiple sclerosis.
Number | Date | Country | Kind |
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2003-406750 | Dec 2003 | JP | national |