Alzheimer's disease (AD) is the most common form of dementia in the elderly, affecting more than 5 million Americans, as well as their families and caregivers. Unfortunately, aging of the global population is only worsening the AD ?epidemic?, as incidence is projected to triple by 2050. Despite intense research, there is currently no cure for this devastating neurodegenerative disorder. Thus, understanding the intrinsic molecular mechanisms that drive AD pathology and progression is critical to devising effective treatments. Postmortem examination of human brains has revealed that AD-associated neuropathologies, such as neurofibrillary tangles (NFTs) and neurodegeneration, generally arise in a conserved spatio-temporal pattern, affecting transentorhinal regions first, and later extending to limbic and isocortical areas. The molecular and neurochemical bases for such selective neuronal vulnerability (SNV) have long been pursued, as they underlie disease progression and may hold the key to understanding the molecular underpinnings of neurodegeneration, but to date these mechanisms remain elusive. Here, cutting-edge, single-cell technologies will be used to generate a comprehensive, multi-omic atlas of cell types within AD-vulnerable brain regions across different stages of disease. The hypothesis is that specific cell types most dramatically affected by AD pathology within susceptible brain regions are characterized by distinct molecular pathways (transcription factors, signaling cascades, gene networks) that drive SNV. Moreover, that these pathways are executed in a sequential spatio-temporal pattern by changes in chromatin architecture and gene regulatory elements. Tracking the molecular changes exhibited by these neuronal cell populations in the continuum of AD pathology will better define AD onset and progression, and potentially indicate new therapeutic targets. Postmortem brain samples will be obtained from healthy controls, or patients who at death exhibited different stages of AD pathology, namely early (Braak III/IV), or late (Braak V/VI). Changes occurring at different stages of AD progression will be analyzed to identify the cell types and molecular pathways most critical for the initiation and spread of AD-related pathology. Regions analyzed will be hippocampus (CA1/sub), inferior temporal cortex (BA20), frontal cortex (BA9), and visual cortex (an AD- resistant region).
In Aim 1, samples from control subject will be subjected to single cell analyses to characterize the methylome and chromatin architecture jointly (sn-m3C-seq), as well as chromatin accessibility together with transcriptome (Paired-seq), of cell types within AD-vulnerable brain regions. Integration of these datasets will create a multi-omic atlas of relevant cell types that will serve as the foundation for understanding AD onset and progression.
In Aim 2, these analyses will be extended to AD patients. Comparing data sets across brain regions and disease stages will reveal the specific cell types most affected in AD, as well as the molecular pathways (based on changes in methylation patterns, chromatin architecture, etc.) that drive SNV in AD (Aim3).
In Alzheimer's disease, certain brains regions exhibit signs of dysfunction and degeneration before others, but the mechanisms underlying this selective vulnerability remain unclear. Here we will isolate tissue samples from AD-vulnerable brain regions at different stages of disease progression and subject them to a range of cutting- edge, single-cell molecular analyses. These data will provide important insights into which cell types are affected, and which molecular pathways drive neuronal dysfunction or death, thereby creating novel avenues for developing effective therapies against this devastating neurodegenerative disease.
