BAIAP3 (BAI1 associated protein 3) is a C2 domain-containing protein that functions primarily in endosome-to-Golgi retrograde transport and regulation of dense-core vesicle (DCV) exocytosis 1. As a member of the Munc13 protein family, BAIAP3 localizes to endosomes and mediates calcium-stimulated interactions with trans-Golgi network (TGN) SNAREs and membrane phospholipids to facilitate endosome fusion with the TGN 1. Unlike other Munc13 proteins that directly regulate exocytosis, BAIAP3 functions indirectly by controlling DCV maturation through recycling of secretory vesicle transmembrane proteins, thereby maintaining DCV protein homeostasis and supporting neurotransmitter and hormone secretion 1. The protein shows brain-specific expression patterns in regions including the amygdala, hypothalamus, and periaqueductal gray 2. Disease relevance includes associations with anxiety disorders and benzodiazepine abuse, with gender-specific effects observed in both mice and humans 2. BAIAP3 has been identified as a significantly mutated gene in cervical adenocarcinomas and serves as a transcriptional target of the oncogenic EWS-WT1 fusion protein in desmoplastic small round cell tumors 34. Recent evidence suggests biallelic loss-of-function variants may cause retinitis pigmentosa through ciliary dysfunction and disrupted Sonic hedgehog signaling 5.