The C677T polymorphism of the methylenetetrahydrofolate reductase gene in Mexican mestizo neural-tube defect parents, control mestizo and native populations

The C677T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene, associated with the thermolabile form of the enzyme, has reportedly been f ound to be increased in neural-tube defects (NTD), though this association is still unclear. A group of 107 mestizo parents of NTD children and five c ontrol populations: 101 mestizo (M), 50 Huichol (H), 38 Tarahumara (T), 21 Purepecha (P) and 20 Caucasian (C) individuals were typed for the MTHFR C67 7T variant by the PCR/RFLP (Hinf1) method. Genotype frequencies were in agr eement with the Hardy-Weinberg expectations in all six populations. Allele frequency (%) of the C677T variant was 45 in NTD, 44 in M, 56 in H, 36 in T , 57 in P, 35 in C. Pairwise inter-population comparisons of allele frequen cy disclosed a very similar distribution between NTD and M groups (exact te st, P = 0.92). Among controls, differences between M and individual native groups were NS (0.06 < P < 0.21), as it was between M and C (P = 0.29). A h igh frequency of the variant was found in H (56 %) and P (57 %). A similar allele frequency in groups M and NTD does not support a causal relationship between NTD and parental MTHFR C677T genotypes. Thus, the C677T valiant ca nnot be regarded as a major genetic risk factor for NTD in Mexican mestizo parents. Otherwise, C677T in Mexico is very frequent, especially in Huichol and Purepecha natives, as compared with other groups world wide. (C) 2000 Editions scientifiques et medicales Elsevier SAS.