A Human iPSC-Based Model to Investigate FUS-Linked ALS Pathogenesis

Abstract Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive loss of upper and lower motor neurons, typically leading to mortality within 1 to 5 years of onset. Mutations in the Fused in Sarcoma (FUS) gene, particularly the aggressive R495X nonsense mutation, represent a critical driver of familial ALS. While induced pluripotent stem cell (iPSC)-based models have advanced our understanding of the disease, most existing studies rely on fibroblast-derived lines obtained through invasive biopsies. In this study, we established a novel patient-specific and healthy control human iPSC platform derived from minimally invasive keratinocytes. This approach offers a significant advantage over traditional models due to the higher reprogramming efficiency and rapid kinetics associated with keratinocyte to iPSC conversion. Our characterization confirmed hallmark pluripotency and trilineage differentiation potential in both lines. Crucially, we observed that FUS-mutant iPSCs exhibit significantly reduced proliferation and increased apoptotic activity via Cleaved Caspase-3 activation. Furthermore, we report a novel pathological feature, the aberrant nuclear aggregation of HDAC1 in the FUS-mutant line. This finding suggests that epigenetic dysregulation and altered nuclear protein homeostasis occur at the earliest stages of cellular development in FUS-ALS. Our keratinocyte-derived iPSC model provides a robust, high-efficiency tool for investigating early pathogenesis and testing targeted therapeutic strategies.