Polymorphisms within the vitamin B12 dependent methylmalonyl-coA mutase are not risk factors for neural tube defects

Methionine synthase and methylmalonyl-CoA mutase (mutase) are the only two known vitamin B12 (B12) dependent enzymes in humans. A lower level of B12 has been shown to be an independent maternal risk factor for neural tube defects (NTDs) prompting an investigation of common genetic variants within B12 dependent enzymes. To investigate the role of methylmalonyl-CoA mutase variants we studied 279 complete NTD triads (NTD affected case and both parents) and 256 controls. Based on case-control and family based (transmission disequilibrium test) analyses we did not find an association between the mutase single nucleotide polymorphisms (SNPs) K212K (636A (longrightarrow) G), H532R (1595A (longrightarrow) G) and V671I (2011G (longrightarrow) A) and NTDs. However, there was a significant difference in the frequencies of these polymorphisms between a group of African Americans and American Caucasians (K212K, P=0.002; H532R, P<0.001; V671I, P=0.006). In conclusion, common variants in the mutase gene do not appear to be risk factors for NTDs but their allele frequencies are significantly different between ethnic groups.