Analysis of two mutations in the MTHFR gene associated with mild hyperhomocysteinaemia – heterogeneous distribution in the South African population

Objective , The frequencies of mutations 677C→T and 1298A→C in the methylenetetrahydrofolate reductase (MTHFR) gene, previously shown to be associated with decreased enzyme activity that may lead to  hyperhomo cysteinaemia and consequently increased risk of cardiovascular disease (CVD), were determined in the South African population. Methods , Hinfi (677C→T) and MbolI (1298A→C) restriction enzyme analyses were performed on amplified DNA samples of 76 white, 73 coloured and 60 black subjects. Results , The mutant alleles of mutations 677C→T and 1298A..-+C were more common in the white (allele frequencies 0.36 and 0.37, respectively) than in the black population (0.04 and 0.09), while intermediate frequencies were detected in the coloured population (0,18 and 0.30); Homozygosity for mutation 677C → T was not detected in the black cohort, while this genotype was detected in 1 coloured (1.4%) and 8 white (105%) subjects, In the black population, 5% of the 60 subjects analysed were homozygous for mutation 1298A→C, compared with approximately 12% in both the white and coloured populations, Conclusions . Since hyperhomocysteinaemia is a risk factor for premature CVD, the heterogeneous distribution of the 677C→T and 1298A→C mutations across ethnic groups may partly explain ethnic differences in heart disease risk through decreased enzyme activity and hence increased homocysteine levels.