ANALYSIS OF THE 677-C-]T MUTATION OF THE METHYLENETETRAHYDROFOLATE REDUCTASE GENE IN DIFFERENT ETHNIC-GROUPS

A recently described mutation in the methylenetetrahydrofolate reducta se (MTHFR) gene (a C to T transition at nucleotide 677) is associated with a thermolabile phenotype and decreased enzyme activity. In homozy gotes, the mutation is also related to hyperhomocysteinemia and increa sed risk for atherosclerotic disease and (apparently) venous thrombosi s. The prevalence of this mutation in different human populations is u nknown. We have investigated the frequency of the 677 C-->T mutation i n the MTHFR gene in 337 individuals (674 chromosomes) belonging to fou r ethnic groups: Whites, African and Brazilian Blacks, Asians and Amer indians. The frequencies of the positive allele among Whites and Asian s were similar to those previously reported for Caucasian populations. The positive allele seems to be slightly rarer among the Amerindians (frequency 24.0%) in comparison to Whites and Asians, with a heterogen eous distribution among the five Indian tribes analysed. In contrast, the mutation has a very low prevalence in Blacks, especially among the African Blacks, for whom the mutation was absent in homozygosity. Our data indicate that the 677 C-->T MTHFR mutation has a significantly h eterogeneous distribution among different ethnic groups, a fact that m ay contribute to explain geographical or racial differences in the ris k for vascular disease.