Project Summary/Abstract The long-term objectives of this application are to: (1) determine how each individual cell type-derived laminin changes in the basement membrane (BM) under both physiological and pathological conditions, and (2) correlate these laminin alterations with AD pathology to screen for unique laminin changes that are useful in early AD diagnosis (before the onset of dementia or A?/tau pathology) and prognosis prediction. This proposal aims to generate an innovative laminin knock-in mouse line that enables accurate assessment of laminin expression in a cell-specific and Cre-dependent manner; and determine the temporary and spatial expression profile of each individual cell type-derived laminin in the BM in normal and AD brains. We have successfully generated the Laminin-mCherry/eGFP knock-in mouse line using CRISPR-Cas9 technique and further validated these mice in the presence and absence of Cre recombination. In Aim 1, we will cross these laminin knock-in mice with various Cre lines to generate a series of cell-specific laminin reporter (Lam-Rep) mice. Using these Lam-Rep mice, we will determine the cellular source of laminin in brain BM, estimate their relative abundance, and characterize the temporary and spatial expression profile of each individual cell type-derived laminin during normal aging. In Aim 2, cell-specific Lam-Rep mice will be crossed into the 5xFAD background. The temporary and spatial expression profile of each individual cell-derived laminin in the resulting Lam-Rep-5xFAD mice and their non-AD Lam-Rep littermates will be determined similarly as described in Aim 1. Successful completion of this study will fill the gap of knowledge in the field by elucidating the cellular source of laminin in brain BM and characterizing the temporary/spatial expression profile of each individual cell type-derived laminin under both normal and AD conditions. These findings will enable correlation studies between loss of specific cell type-derived laminin and AD pathology; and may identify unique laminin changes that are useful in early AD diagnosis and prognosis prediction. In addition, this proposal will also address a critical barrier to progress in the field by generated an innovative laminin knock-in mouse line, which allows labeling of laminin in a cell-specific and Cre- dependent manner. This genetic tool is also valuable to researchers in other fields (e.g. in vivo imaging and leukocyte transmigration). These studies will lead to a breakthrough in laminin/BM research and substantially move the field forward.