SORL1 and its involvement in Alzheimer's disease pathogenesis and pathophysiology - Core C: Human Induced Pluripotent Stem Cell (hiPSC)

Columbia University Health Sciences, New York NY

Investigators

Abstract

CORE C SUMMARY As discussed in the Overview, the overall goal of this PPG is to understand the pathogenicity and pathophysiology of disease-associated variants in the Alzheimer's disease gene SORL1. AD is a major leading cause of death in the developed world and there are currently no preventative or significantly disease-modifying treatments. SORL1 is emerging as only the 4th gene that is considered causal in Alzheimer's disease, and new insight shows how the SORL1 protein interacts with the retromer trafficking complex in mediating the disease's cardinal pathologies. The overall approach in the PPG is to study a unified set of SORL1 variants that are predicted to be pathogenic based on a recently developed prioritization framework (see Overview). The overall PPG consists of four Cores and four Projects that together will pursue hypothesis-based experiments to test how SORL1 variants affect retromer-dependent endosomal recycling as well as unbiased approaches to explore and expand the mechanistic understanding of how SORL1 drives and/or modulates AD pathogenesis. Core C will support the overall Program Project by generating and characterizing isogenic human induced pluripotent stem cell (hiPSC) lines that harbor 22 selected SORL1 pathogenic variants. We will deliver a comprehensive phenotypic analysis of these variants in hiPSC-derived neurons, astrocytes and microglia. Aim 1 will focus on neuronal phenotypes and include conventional AD read-outs such as A, phospho-Tau and early endosome size. We will also examine novel phenotypes including secretion of Amyloid Precursor-Like Protein 1 (APLP1) secretion, soluble SORL1 (sSORL1) shedding, and cell surface localization of the glutamate receptor subunit, GLUA1. Aim 2 will focus on glial phenotypes. Recent data from our laboratory suggests that SORL1- retromer deficiency may converge on the lysosome in glial cells. We will measure lysosome size and function as well as neuroimmune phenotypes, including phagocytosis and cytokine secretion, and glial functions such as glutamate uptake. Aim 3 will use bulk RNA-sequencing of neuronal and glial cells harboring the different pathogenic variants to identify new mechanistic pathways in an unbiased manner. Core C is well integrated into the overall PPG. We will build upon the biochemical, cell biological, genetic and structural data in Projects 1 and 2 and Cores B and D. The data generated by Core C will inform and complement the mouse models proposed in Project 3 and the biofluidic analyses proposed in Project 4. Together our Core, along with the other Projects and Cores of the PPG, will provide a comprehensive overview of pathogenic SORL1 variants and SORL1-retromer biology in human neurons and glia.