Investigating an African American-specific APOE genetic variant using hiPSC

PROJECT SUMMARY ABSTRACT African Americans are at a significantly elevated risk of Alzheimer’s disease (AD) compared to the non-Hispanic white population. Yet, the underlying mechanisms of this health disparity are significantly understudied. Recently, a variant in Apolipoprotein E (APOE), APOE R145C, was identified as significantly increasing the risk of AD among individuals of African ancestry. Despite this association, the underlying mechanisms of how the presence of this APOE variant exacerbates AD onset and progression in aging adults have yet to be elucidated. As such, we will use our collective experience in stem cell bioengineering, neurodegenerative disease modeling, and genome editing to elucidate the potential mechanisms by which the APOE R145C variant modulates AD risk. To that end, in the first aim, we will use our recently developed highly efficient gene editing approach to introduce the APOE R145C variant into isogenic human induced pluripotent stem cells (hiPSCs) from both non-demented control (NDC) and AD patients including those derived from African American subjects. In turn, in the second aim, biochemical, cellular, and genetic analysis of neuronal, astrocytic, and microglia cultures will be used to determine the effect of the APOE R145C variant on the presence of AD-related phenotypes. In particular, we will determine if APOE R145C exerts its risk modifying effects through (i) modulation of Aβ processing, secretion, or uptake and (ii) alteration in tau hyperphosphorylation and uptake. In addition, whole transcription analysis will be used to identify signaling pathways and transcriptional targets that are modified by the presence of the APOE R145C variant and disease status. Overall, the data obtained as part of this proposal will set the stage for future hypothesis-testing studies to probe the mechanisms by which the African American-associated APOE R145C variant accelerates AD onset. Such investigations will have a significant impact on the design of molecularly targeted therapies to treat AD in the high-risk African American population.