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is agene
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Full namemethylenetetrahydrofolate reductase (NAD(P)H)
# SNPs30
  Max Magnitude Chromosome position Summary
Rs12121543 11,854,671
Rs121434294 0 11,860,308
Rs121434295 0 11,861,223
Rs121434296 0 11,854,823
Rs121434297 0 11,855,218
Rs13306560 0 11,866,183
Rs13306561 11,865,804
Rs1476413 11,852,300
Rs1537514 11,848,068
Rs17037390 11,860,843
Rs17037396 0 11,862,047
Rs17367504 0 11,862,778
Rs17375901 0 11,852,516
Rs17421511 11,857,788
Rs1801131 2.1 11,854,476
Rs1801133 2.1 11,856,378 elevated homocysteine levels
Rs2066462 0 11,854,896
Rs2066470 0 11,863,057
Rs2274976 0 11,850,927
Rs267606886 0 11,855,171
Rs267606887 0 11,855,215
Rs3737964 11,867,044
Rs3737965 0 11,866,451
Rs45590836 0 11,851,273
Rs4846048 11,846,252
Rs4846049 11,850,365
Rs4846051 0 11,854,457
Rs59514310 11,856,378
Rs7533315 11,860,683
Rs9651118 11,862,214

The MTHFR gene encodes the vitamin-dependent enzyme, methylenetetrahydrofolate reductase. Several conditions or defects caused by functionally impaired forms of the MTHFR protein can be improved through dietary supplementation by folate.

There are 3 common SNPs giving rise to MTHFR alleles:

gs192 and gs193 look at variation in this gene

It is likely that there are numerous other variations that are much rarer. When the MTHFR genes of 564 individuals of diverse ethnicities were fully sequenced, in addition to the 3 common alleles mentioned above, 11 other nonsynonymous changes were found, each with a frequency under 1%. Four of these 11 rarer alleles affected enzyme function (as did A222V) based on tests in yeast, most of which could be fixed with higher folate supplementation (in yeast; this is not yet tested in humans). Since all five impaired alleles map to the N-terminal catalytic domain of the enzyme, it seems likely that additional SNPs causing nonsynonymous changes in this region could have similar effects.10.1073/pnas.0802813105

SNP rs1801133, A222V, is not thought to be a major risk factor for neural tube defects [PMID 17035141] except in certain populations. For example, Dutch and Irish populations indicate an increased risk for (T;T) carriers [PMID 10090889], but this same genotype (ie carriers of the thermolabile T allele) appears to have a protective effect in an Italian population studied [PMID 12111380].

[PMID 16672082] a SNP in MTHFR which affects Neural-tube defects (Birth defects)