FUT2 encodes a fucosyltransferase that catalyzes α-1,2-fucosylation of terminal galactose residues on O- and N-linked glycans of cell surface glycoproteins and glycolipids 123. This enzymatic activity generates the H antigen, an essential substrate for ABO blood group antigen synthesis 2. FUT2 plays a critical role in host-microbe interactions by modulating intestinal glycan structures that regulate gut microbiota composition 45. FUT2 genotype determines secretor status, influencing which oligosaccharide antigens (particularly GalNAc-terminating structures) are available to commensal bacteria, thereby shaping bacterial community structure and function 45. Functionally, reduced FUT2 expression and α-1,2-fucosylation are associated with inflammatory bowel disease susceptibility, with FUT2 deficiency promoting dysbiosis-induced lysophosphatidylcholine generation that damages intestinal epithelial barriers 6. FUT2 variants also show pleiotropic effects across gastrointestinal and psychiatric disorders through shared genetic pathways 7. Conversely, in colorectal cancer, FUT2-dependent fucosylation of LAMP1 promotes apoptosis by regulating the autophagy-lysosomal pathway, suggesting protective antitumor mechanisms 8. FUT2 genetic variants are associated with peptic ulcer disease susceptibility, likely through effects on Helicobacter pylori infection susceptibility 9.