EXTENSIVE POLYMORPHISM OF THE FUT2 GENE IN AN AFRICAN (XHOSA) POPULATION OF SOUTH-AFRICA

The human secretor type alpha(1,2)fucosyltransferase gene (FUT2) polym orphism was investigated in Xhosa and Caucasian populations of South A frica by polymerase chain reaction-restriction fragment length polymor phism 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 sub stitutions, A40G (Ile(14)Val), C379T (Arg(127)Cys), and G481A (Asp(161 )Asn), and two synonymous base substitutions, A375G (Glu(125)) and C48 0T (His(160)), were also identified in functional alleles. As a result , seven new alleles, Se-40, Se-481, Cn(40,481), Se-357,Se-480, Se-357, Se-379,Se-480, Se-375, and se(357,480,778) were identified. Population studies revealed that an allele containing a nonsense mutation G428A (Trp(143)stop) (se(428)) was the common null allele in both Xhosa and Caucasian populations, whereas an allele containing a missense A385T ( Ile(129)Phe) mutation (se(357,385)), which is the common null allele i n Orientals, was found to be absent from both populations. The heteroz ygosity rates of FUT2 genotypes were as high as 0.75 in the Xhosa popu lation and 0.65 in the Caucasian population. Therefore, the extensive polymorphism and race specificity of the FUT2 gene make it suitable fo r application as a new tool in genetic studies of modern human evoluti onary history.