Severe and mild mutations in cis for the methylenetetrahydrofolate reductase (MTHFR) gene, and description of five novel mutations in MTHFR

Am J Hum Genet. 1996 Dec;59(6):1268-75.


Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate, a methyl donor in the conversion of homocysteine to methionine. Patients with severe MTHFR deficiency have hyperhomocysteinemia, hypomethioninemia, and a range of neurological and vascular findings with a variable age at onset. We have previously described nine mutations in patients with severe MTHFR deficiency. A mild form of MTHFR deficiency, associated with a thermolabile enzyme, has been proposed as a genetic risk factor for cardiovascular disease and for neural tube defects. We have shown that a common missense mutation (an alanine-to-valine substitution) encodes this thermolabile variant. We now report an additional five mutations causing severe MTHFR deficiency and an analysis of genotype (alanine/valine status) and enzyme thermolability in 22 patients with this inborn error of metabolism. Six of these patients have four mutations in the MTHFR gene-two rare mutations causing severe deficiency and two mutations for the common alanine-to-valine mutation that results in thermolability. Even in severe MTHFR deficiency, the thermolabile variant is frequently observed, and there is a strong relationship between the presence of this variant and increased enzyme thermolability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Alanine
  • DNA Mutational Analysis
  • Female
  • Genotype
  • Heterozygote
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Methylenetetrahydrofolate Reductase (NADPH2)
  • Oxidoreductases Acting on CH-NH Group Donors / deficiency*
  • Oxidoreductases Acting on CH-NH Group Donors / genetics*
  • Point Mutation / genetics*
  • Valine


  • Oxidoreductases Acting on CH-NH Group Donors
  • Methylenetetrahydrofolate Reductase (NADPH2)
  • Valine
  • Alanine