FUT2

FUT2, also known as fucosyltransferase 2, is a human gene that encodes the enzyme alpha(1,2)-fucosyltransferase 2. This Golgi-resident enzyme catalyzes the transfer of fucose in an alpha-1,2 linkage from GDP-fucose to galactose on precursor chains, forming the H antigen that underlies the secretor form of the histo-blood group antigens in mucosal secretions and body fluids. The FUT2 gene is located on chromosome 19 at the 19q13.3 region.

Secretor status is determined by FUT2 activity. Individuals with at least one functional FUT2 allele (secretors) express ABH antigens in saliva, breast milk, tears, and other secretions. Those who are homozygous for nonfunctional FUT2 alleles (nonsecretors) lack H antigen in secretions, though ABH antigens can still appear on red blood cells via FUT1 activity. The secretion phenotype can influence glycan patterns on mucosal surfaces and fluid interfaces, affecting interactions with microbes and the immune system.

Genetic variation in FUT2 includes a common nonfunctional allele arising from a G to A substitution at nucleotide 428 (G428A), which creates a stop codon and yields the nonsecretor form. The functional allele is typically referred to as Se, while the nonfunctional allele is se. The Se/Se and Se/se genotypes confer secretor status, whereas the se/se genotype confers nonsecretor status. The frequency of secretors versus nonsecretors varies across populations.

Biological and clinical significance includes the influence of FUT2 on susceptibility to certain pathogens and on the composition of the gut microbiota. Nonsecretors show reduced susceptibility to some strains of norovirus that require secretor-type glycans for binding, while other strains can overcome this barrier. Secretor status also contributes to natural variation in mucosal glycan landscapes and related host–microbe interactions.