<i>FLVCR1a</i> REGULATES CORTICAL INTERNEURON DEVELOPMENT AND MIGRATION IN THE EMBRYONIC CORTEX

FLVCR1 (feline leukemia virus subgroup C receptor 1) is a solute carrier protein implicated in choline and ethanolamine transport, highly expressed in the developing brain. Biallelic pathogenic variants in FLVCR1 are associated with a broad spectrum of neurological disorders, including congenital hydrocephalus, microcephaly, developmental delay, epileptic encephalopathy, and adultonset neurodegeneration. While Flvcr1a deletion in neural progenitor cells (NPCs) disrupts mitochondrial calcium homeostasis and energy metabolism leading to defective neurogenesis and congenital hydrocephalus, this does not fully account for the cognitive symptoms observed in patients. Here, we explore the contribution of FLVCR1a to cortical interneuron development, as these GABAergic neurons are essential for the formation of neuronal networks. Using a conditional knockout mouse model lacking Flvcr1a in NPCs, we observed altered interneuron migration, characterized by reduced interneuron migration rates, shortened leading processes, and aberrant direction changes, along with altered morphology in vitro. Additionally, explants of medial ganglionic eminence (MGE) from mutant embryos displayed migration deficits compared to wild-type littermates. To dissect the molecular mechanism, we investigated the FLVCR1a protein interactome and identified DOCK7, a Rac1 guanine nucleotide exchange factor, and CRAD, an inhibitor of F-actin capping proteins, as FLVCR1a interactors. Additionally, by using a FRET biosensor, we reported that FLVCR1a modulates Rac1 activity a key regulator of cytoskeletal organization during migration. These findings link FLVCR1a to the regulation of cytoskeletal dynamics and cell polarity in migrating interneurons. These findings suggest that FLVCR1a deficiency disrupts cellular migration and morphology during development, likely through the modulation of cell bioenergetics and cytoskeletal dynamics. This study contributes to a deeper understanding of neurodevelopmental disorders linked to FLVCR1a mutations.