SGSM3 encodes a GTPase-activating protein (GAP) that specifically regulates Rab5 small GTPase by accelerating its intrinsic GTP hydrolysis rate, thereby controlling trafficking through the early endocytic pathway 12. As a member of the RAS superfamily, SGSM3 functions in small G protein signaling modulation and vesicular transport processes. The protein localizes to cytosol, endosomal compartments, Golgi apparatus, and plasma membrane, where it regulates endocytosis and protein trafficking 3. SGSM3 demonstrates significant disease relevance across multiple conditions. Homozygous loss-of-function variants cause an intellectual disability syndrome characterized by mild global developmental delay, moderate intellectual disability, hypotonia, behavioral challenges, and short stature, particularly identified in Ashkenazi Jewish populations 45. The gene also shows tumor suppressor properties in cancer, with decreased expression observed in breast cancer 6 and hepatocellular carcinoma tissues 7. Polymorphisms in SGSM3 are associated with cancer susceptibility and survival outcomes 893. Additionally, SGSM3 variants may predispose to schwannomatosis 10. The protein's role in vesicular transport appears critical for normal neurodevelopment and cellular homeostasis.