PROJECT SUMMARY: Age and the ɛ4 allele of apolipoprotein E (apoE) are the two greatest risk factors for developing Late Onset Alzheimer’s Disease (LOAD). As there is no known cure for or cause of LOAD, understanding the mechanism underlying known risk factors is paramount for moving therapeutic research forward. ApoE mediates its physiological effects in the brain by binding to cognate receptors like apoER2, which is found in multiple splice isoforms or variants that are precisely regulated. Recent studies have discovered a novel link between aging, neurodegeneration and alternative splicing. Interestingly, alternative splicing of the apoE receptor apoER2 is altered in Alzheimer’s disease (AD). Therefore, abnormal alternative splicing in aging and neurodegeneration may alter the interactome of the key AD risk factor APOE through apoER2, influencing APOE physiological function and highlighting a new scientific paradigm through which to investigate the role of APOE in LOAD. The overall goal of this proposal is to investigate whether splicing of apoER2 is altered in AD and to uncover modifiers of apoER2 splicing events. The central hypothesis is that apoER2 isoform balance is perturbed in AD due to altered posttranslational regulation of splicing factors, correlating with pathology development across the brain. To investigate this hypothesis, two specific aims are proposed. In Aim 1, the isoform distribution of apoER2 will be determined across AD Braak stage and brain region compared to healthy individuals using single molecule long read sequencing and qPCR. In Aim 2, regulation of a specific apoER2 splicing event by a splicing factor will be probed using a variety of in vitro techniques including RNA- Immunoprecipitations, splicing reporter assays and gel shift assays. Completion of this proposal will be highly significant, providing a novel scientific model through which to view conferred APOE risk in AD: altered splicing regulation of the cognate receptor apoER2. This proposal incorporates bioinformatics, synaptic biology and RNA biology into one integrated training plan providing the applicant a well-rounded and rich fellowship training experience. This is accomplished by an expansive network of supporting sponsors and collaborators who have pledged to guide the applicant through the proposed research and facilitate her development into an independent research neuroscientist.