Extensive polymorphism of the FUT2 gene in an African (Xhosa) population of South Africa

Abstract

The human secretor type α(1,2)fucosyltrans-ferase gene (FUT2) polymorphism was investigated in Xhosa and Caucasian populations of South Africa by polymerase chain reaction–restriction fragment length polymorphism and DNA sequencing. Six new base substitutions were found in the coding region of FUT2. A single base (C) deletion at nucleotide 778, which led to a frame shift and produced a stop codon at codon 275, was responsible for the enzyme inactivation. Three nonsynonymous base substitutions, A40G (Ile¹⁴Val), C379T (Arg¹²⁷Cys), and G481A (Asp¹⁶¹Asn), and two synonymous base substitutions, A375G (Glu¹²⁵) and C480T (His¹⁶⁰), were also identified in functional alleles. As a result, seven new alleles, Se ⁴⁰ , Se ⁴⁸¹ , Se ^40,481 , Se ^357,480 , Se ^357,379,480 , Se ³⁷⁵, and se ^357,480,778 were identified. Population studies revealed that an allele containing a nonsense mutation G428A (Trp¹⁴³stop) (se ⁴²⁸) was the common null allele in both Xhosa and Caucasian populations, whereas an allele containing a missense A385T (Ile¹²⁹Phe) mutation (se ^357,385), which is the common null allele in Orientals, was found to be absent from both populations. The heterozygosity rates of FUT2 genotypes were as high as 0.75 in the Xhosa population and 0.65 in the Caucasian population. Therefore, the extensive polymorphism and race specificity of the FUT2 gene make it suitable for application as a new tool in genetic studies of modern human evolutionary history.