PROJECT SUMMARY Dementia with Lewy body (DLB) has been historically under-investigated relative to its prevalence as most studies of synucleinopathies focus on PD and PDD. Accumulating evidence indicates, however, DLB is a distinct age-associated neurodegenerative dementia. Like PD, various types of cells including neurons, microglia, astrocytes, oligodendrocytes, endothelial cells, and peripheral lymphocytes might contribute to DLB pathogenesis. To understand complexities of DLB pathogenesis, more comprehensive approaches to investigating different cell types and multiple brain regions over the course of disease progression are necessary. Our lab has put extensive effort into single-nuclei analysis of postmortem brain tissues using a recently released Chromium Single-Cell Multiome ATAC plus Gene Expression platform (10X Genomics) and successfully established all key techniques and a data analysis pipeline. To track the progression of disease using both RNA- and ATAC-seq data in the same cell, we have developed a novel strategy: “correlated pseudo-pathogenesis (cPP)” trajectory analysis. We also established “gene-peak” analysis allowing us to analyze relationships between gene expression and chromatin accessibility in a single cell. Our technical advancements and innovative data analysis skills will satisfy this FOA requesting “projects to identify cellular changes in ADRD post- mortem brain tissue across disease progression.” To achieve the goal set by the current FOA, we will pursue the following aims: Aim 1. Neuropathological staging of DLB and validation of control postmortem samples. Postmortem brain tissues from the HBTRC will be further validated for neuropathological staging by H&E and α- SYN immunohistochemical staining according to Unified Staging System for Lewy Body Disorders (USSLB). To eliminate incidental Lewy body disease (ILBD), control tissues will also be investigated for α-SYN pathology. Aim 2. Isolate nuclei from each sample and perform snRNA-seq and snATAC-seq analysis. 4 brain regions from three groups: 1) control; 2) stage II (limbic or brainstem predominant)/III (both limbic and brainstem); 3) and stage IV (neocortical), will be subject to single-nuclei multiomic analysis. Aim 3. Spatial transcriptomic analysis for topological domain mapping. Differential gene expression in the specific microdomains of each brain region and relationship to α-SYN pathology will be investigated using a spatially barcoded gene expression profiling array.