RAB3GAP1 encodes the catalytic subunit of the RAB3 GTPase-activating protein complex that plays critical roles in membrane trafficking and neurodevelopment. The protein functions as both a GTPase-activating protein (GAP) for RAB3 subfamily members and a guanine nucleotide exchange factor (GEF) for RAB18, regulating vesicular transport at the endoplasmic reticulum and Golgi apparatus 1. RAB3GAP1 is essential for autophagy regulation, modulating both basal and rapamycin-induced autophagosome formation through interactions with ATG proteins and lipid droplet organization 2. The protein promotes phagophore biogenesis by facilitating endosome-ER contact sites and creating localized environments for autophagy initiation 3. In neurons, RAB3GAP1 regulates neurite outgrowth and complexity through interactions with axon elongation factors like DOCK7 and ER-Golgi trafficking modulators like TMF1 4. Loss-of-function mutations in RAB3GAP1 cause Warburg Micro syndrome, characterized by microcephaly, intellectual disability, and ocular abnormalities 56. The protein is also implicated in cholesterol biosynthesis, as RAB3GAP1-deficient cells accumulate cholesterol precursors and show impaired de novo cholesterol synthesis 1. Additionally, RAB3GAP1 dysfunction contributes to congenital disorders of autophagy, representing a novel class of neurodevelopmental conditions 7.