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SNP: rs1801133
Name(s) C677T, Ala222Val, A222V
Chromosome 1
External databases
Ensembl Human SNPView
dbSNP 1801133
HapMap 1801133
SNPedia 1801133
AlzGene Meta-analysis
SzGene Meta-analysis

C677T or rs1801133 is a genetic variation—a single nucleotide polymorphism (SNP)—in the MTHFR gene.

Among Americans the frequency of T-homozygosity ranges from 1% or less among people of sub-Saharan African descent to 20% or more among Italians and Hispanics.[1]

It has been related to

In 2000 association studies on oral clefts, Down syndrome, and fetal anticonvulsant syndrome were either unreplicated or had yielded conflicting results.[1]

Related genetic variants[edit]

A1298C is a SNP in the same gene. Studies have investigated the combined effect of C677T and A1298C.[6]


  1. ^ a b c L. D. Botto & Q. Yang (May 2000). "5,10-Methylenetetrahydrofolate reductase gene variants and congenital anomalies: a HuGE review". American Journal of Epidemiology. 151 (9): 862–867. doi:10.1093/oxfordjournals.aje.a010290. PMID 10791559.
  2. ^ "Meta-Analysis of All Published Schizophrenia-Association Studies (Case-Control Only) for (C677T) polymorphism, MTHFR gene". Schizophrenia Research Forum. Archived from the original on 2012-03-21. Retrieved 2007-03-11.
  3. ^ "Meta-analysis of all published AD association studies (case-control only)". Alzheimer Research Forum. Archived from the original on 2012-03-21. Retrieved 2008-08-02.
  4. ^ S. J. Lewis, D. A. Lawlor, G. Davey Smith, R. Araya, N. Timpson, I. N. M. Day & S. Ebrahim (April 2006). "The thermolabile variant of MTHFR is associated with depression in the British Women's Heart and Health Study and a meta-analysis". Molecular Psychiatry. 11 (4): 352–60. doi:10.1038/ PMID 16402130.
  5. ^ Schmidt, Rebecca J.; Hansen, Robin L.; Hartiala, Jaanad; Allayee, Hoomand; Schmidt, Linda C.; Tancredi, Daniel J.; Tassone, Florab; Hertz-Picciotto, Irvaa. "Prenatal Vitamins, One-carbon Metabolism Gene Variants, and Risk for Autism". Epidemiology. Retrieved 2011-06-20.
  6. ^ Naomi Q. Hanson, Ömer Aras, Feng Yang & Michael Y. Tsai (April 2001). "C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase gene: incidence and effect of combined genotypes on plasma fasting and post-methionine load homocysteine in vascular disease". Clinical Chemistry. 47 (4): 661–666. PMID 11274015.