PROJECT SUMMARY/ABSTRACT LATE-NC (limbic-predominant age-related transactive response DNA-binding protein of 43 kDa [TDP-43] encephalopathy neuropathological change), a recently recognized form of TDP-43 proteinopathy, is the third most impactful cause of dementia following Alzheimer’s disease neuropathologic change (ADNC) and cerebrovascular disease, accounting for 15-20% of all dementia cases in older adults. Genetic association studies by our group and others revealed unique, LATE-NC-specific risk loci as well as those shared with other common dementia-causing proteinopathies. A transcriptomic study from our group implicated endo-lysosomal dysregulation as a crucial pathophysiologic process underlying LATE-NC. However, molecular and cellular underpinnings of LATE-NC remain largely unknown: we do not even have the knowledge to develop in vitro/in vivo disease models or nominate target pathways, and as a result, we cannot diagnose, treat, or prevent LATE-NC in living persons yet. Defining molecular and cellular changes underlying LATE-NC is a prerequisite to developing translatable in vitro/in vivo disease models and identifying biomarker/therapeutic targets. This critical knowledge gap has been acknowledged by the NIH AD-Related Dementias (ADRD) Summit in 2022, which made a high-priority recommendation to investigate molecular changes associated with LATE-NC. Therefore, this proposal aims to define the transcriptomic, proteomic, and cellular underpinnings of LATE-NC in the human amygdala, the brain region where LATE-NC is thought to originate. Our central hypothesis is that, in the amygdala, endo-lysosomal dysregulation, altered RNA metabolism, glial dysfunction, and neuronal loss underlie LATE-NC pathophysiology. To test the central hypothesis, we propose to generate and analyze transcriptomic, proteomic, and single-nucleus multiome (transcriptome and chromatin accessibility) data from the post-mortem amygdala samples from the extensively characterized Religious Orders Study and Rush Memory and Aging Project participants (n=480). We will pursue the following three specific aims: First, we will determine the transcriptomic underpinnings of LATE-NC. Second, we will identify the proteomic signature of LATE-NC. Third, we will define the single-cell landscape of LATE-NC. We will use statistical modeling approaches to infer causal relationships. We will consider sex-specific effects and the confounding effect of comorbid ADNC pathology throughout the study. The expected outcomes of this project will nominate protein biomarker targets and define plausible upstream and downstream events of LATE-NC. These results will guide our future studies to develop in vitro and possibly in vivo LATE-NC models and, eventually, targeted therapeutics. The large-scale amygdala multi-omic data will be broadly shared with the scientific community to support numerous ADRD research projects, ensuring a significant lasting impact in neurodegeneration research far beyond th...