Kelly et al. (1995) found that a nonsense mutation involving codon 143 (numbered from the putative initiator methionine of the short FUT2 protein) is responsible for the nonsecretor phenotype. See also Rouquier et al. (1995). The nonsense mutation was due to a G-to-A transition at nucleotide 428. However, the trp143-to-ter mutation found in ethnic groups other than Japanese was not found in any of 45 Japanese nonsecretors. Instead, 2 novel mutations, a C-to-T transition at nucleotide 357 and an A-to-T transversion at nucleotide 385 were found in Japanese nonsecretors. The 357C-T mutation was silent insofar as amino acid substitution was concerned; the 385A-T missense mutation (182100.0002) resulted in inactivation of the alpha(1,2)fucosyltransferase.
Vitamin B12 Plasma Level Quantitative Trait Locus 1
Hazra et al. (2008) found that 3 single-nucleotide polymorphisms in the FUT2 gene, including rs601338, which encodes the W143X variant, are in strong linkage disequilibrium and are strongly associated with plasma levels of vitamin B12 as a quantitative trait (B12QTL1; 612542). Hazra et al. (2008) considered the W143X polymorphism to be a plausible causal variant for this association.
Norwalk Virus Infection, Resistance to
Lindesmith et al. (2003) found that individuals who are homozygous for the FUT2 428G-A allele in the ABH histo-blood group family do not express the H type-1 oligosaccharide ligand required for Norwalk virus binding. The FUT2 susceptibility allele is fully penetrant against Norwalk virus infection as none of these individuals developed an infection after challenge, regardless of dose. Of the susceptible population that encoded a functional FUT2 gene, a portion was resistant to infection, suggesting that a memory immune response or some other unidentified factor also affords protection from Norwalk virus infection.