Identification of a New Plasma α(1,3)Fucosyltransferase (FUT6) Allele Requires an Extended Genotyping Strategy

Abstract

Screening the FUT6 gene of 40 Swedish individuals, originally selected for genotyping of FUT3, revealed an unexpected high frequency of mutations. Four were originally typed as homozygous for the enzyme lethal mutation G739A by Taq alpha I restriction pattern, but only one lacked plasma alpha(1,3)fucosyltransferase activity. Cloning and sequencing of FUT6 from 2 of them revealed a new allele, without the G739A mutation, but with two new point mutations C738T and G977A. Segregation of this allele was confirmed in Swedish and Indonesian families. Since G739A and C738T mutations are only one nucleotide apart and induce the same modification of Taq alpha I cleavage, a new screening strategy for FUT6 was adopted. The homozygous inactivating G739A mutation was for the first time identified in Caucasian and Polynesian individuals, both lacking plasma enzyme activity. The mutation C370T was present in 25 of the 40 Swedish individuals and the inactivating mutation C945A was not found at all. These findings stress the dangers of transferring restriction enzyme genotype strategies from one population to another and of inferring phenotypes from genotypes without phenotyping and/or performing confirmatory cloning and sequencing.

Identification of a Missense Mutation (G329A; Arg110→ Gln) in the Human FUT7 Gene

“…Point mutations inactivating or disrupting Fuc-TIII (␣1,3/1,4-fucosyltransferase, Lewis enzyme) give rise to Lewis negative phenotypes (21)(22)(23)(24). Inactivating mutations have also been found in the FUT6 gene coding for the plasma ␣1,3-fucosyltransferase, Fuc-TVI (25)(26)(27)(28). However, there have been no reports on genetic polymorphism in the genes encoding for the ␣1,3-fucosyltransferases expressed in human leukocytes.…”