GALNT16 encodes polypeptide N-acetylgalactosaminyltransferase 16, a Golgi-localized enzyme that catalyzes the initial step of O-linked oligosaccharide biosynthesis by transferring N-acetyl-D-galactosamine residues to serine or threonine residues on protein receptors. This enzymatic activity initiates mucin-type O-linked glycosylation, a critical post-translational modification affecting protein function. Genetically predicted elevated GALNT16 levels show protective effects against diabetic retinopathy risk (OR = 0.832; P = 0.008), identifying it as a potential therapeutic target 1. In cancer contexts, GALNT16 polymorphisms associate with breast cancer susceptibility in Chinese populations, with specific variants linked to increased risk in younger patients and correlation with tumor progression markers 2. Conversely, circular RNA derived from GALNT16 suppresses colorectal cancer progression by enhancing hnRNPK SUMOylation and hnRNPK-p53 complex formation, which inhibits pro-tumorigenic Serpine1 expression 3. GALNT16 was identified as a tumor-specific antigen in hepatocellular carcinoma relevant for mRNA vaccine development 4. Additionally, GALNT16 variants associate with cardiovascular disease through lipid metabolism pathways 5, and the gene has been implicated in milk composition traits in dairy cattle 6. Recent evidence links GALNT16 variants to familial schizophrenia, suggesting aberrant glycosylation may contribute to neuropsychiatric pathology 7.