Mutations in GFAP Disrupt the Distribution and Function of Organelles in Human Astrocytes

Summary: How mutations in glial fibrillary acidic protein (GFAP) cause Alexander disease (AxD) remains elusive. We generated iPSCs from two AxD patients and corrected the GFAP mutations to examine the effects of mutant GFAP on human astrocytes. AxD astrocytes displayed GFAP aggregates, recapitulating the pathological hallmark of AxD. RNA sequencing implicated the endoplasmic reticulum, vesicle regulation, and cellular metabolism. Corroborating this analysis, we observed enlarged and heterogeneous morphology coupled with perinuclear localization of endoplasmic reticulum and lysosomes in AxD astrocytes. Functionally, AxD astrocytes showed impaired extracellular ATP release, which is responsible for attenuated calcium wave propagation. These results reveal that AxD-causing mutations in GFAP disrupt intracellular vesicle regulation and impair astrocyte secretion, resulting in astrocyte dysfunction and AxD pathogenesis. : Jones et al. study the structure function relationship of GFAP on astrocytes using Alexander disease patient-derived induced pluripotent stem cells. Mutations in GFAP result in mislocalization of organelles and functional consequences such as reduced ATP release and attenuated calcium wave propagation. Genetic correction of mutant GFAP rescues these defects. Keywords: Alexander disease, iPSC, CRISPR, endoplasmic reticulum, lysosome