Lizbeth Gonzalez-Herrera, Pilar Flores-Machado, Guadalupe Garcia-Escalante, Ileana Castillo-Zapata, Doris Pinto-Escalante
Universidad Autonoma de Yucatan. Centro de Investigaciones Regionales. Laboratorio de Genetica, Calle 59 No. 490 x Av Itzaez. CP 97000 Merida, Yucatan, Mexico
Neural tube defects (NTD) are the most prevalent congenital anomaly in the State of Yucatan, Mexico. The protective effect of folate on the occurrence of NTD suggests that the study of folate metabolism might identify some of the genetics determinants of NTD. Several candidate genes of folate metabolism have been studied, including MTHFR, CBS, MS and MSR. Two common polymorphisms, C677T and A1298C in the MTHFR gene might be associated with NTD in some populations. Homozygosity for the C677T allele in infants is associated with approximately a 70% increased risk for NTD. Compound heterozygosity for the C677T and A1298C alleles accounts for a proportion of folate related NTDs and might be associated with an increased risk for NTD in comparison with the presence of two wild-type alleles. A common allele on CBS gene, 844ins68 bp, has also been described, although their association with NTD is still unclear. The aim of this study was determine the association between NTD and three common folate polymorphisms (C677T and A1298C in MTHFR and 844ins68 in CBS) in the State of Yucatan, Mexico. We genotyped 75 subjects with NTD, 102 of their respective parents to compare with 110 control subjects with healthy offspring. Polymorphisms were determined by PCR-RFLP's. Allelic, genotypic and haplotypic frequencies were obtained in each group. Genotypic frequencies in control group for the three polymorphisms were according to Hardy-Weinberg expectations (p>0.33). Results did not show any statistically significant difference among allelic, genotype or haplotype frequencies for any of three polymorphisms examined (p>0.05). We did not observe any individual homozygous for 844ins68 bp allele, nor any individual with three or four mutated alleles in MTHFR, haplotypes CT-CC and TT-CC. Our data suggest that in this population of Yucatan, Mexico, alleles C677T and A1298C in MTHFR gene and 844ins68bp in CBS gene are not associated risk factors for NTD, either independently or in combination.
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