DIYgenomics citizen science experiments - MTHFR mutations and Vitamin B12 deficiency

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A. Background

As a proof of concept for DIYgenomics citizen science, this study seeks to replicate and extend existing studies to examine mutations in the MTHFR gene, investigate the potential corresponding phenotype, Vitamin B12 deficiency, and determine if vitamin supplementation or other remedies may improve the deficiency. Coordinating investigators: Melanie Swan, Raymond McCauley 

B. Methodology and Findings

Genotyping values are sought from citizen science participants. Participants that are homozygous and perhaps heterozygous for risk variants will be asked to take a blood test to assess B12 deficiency. Questionnaires are employed to ask participants about Vitamin B12 deficiency. Participants with Vitamin B12 deficiency may begin a vitamin supplementation program or other remedies which are self-tracked with additional blood tests after 3, 6 and 12 months.

1. Gene mutation: MTHFR (Source: Wikipedia: MTHFR)  Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that in humans is encoded by the MTHFR gene.

C677T SNP (Ala²²²Val)

The MTHFR nucleotide at position 677 in the gene has two possibilities: C or T. C at position 677 (leading to an alanine at amino acid 222) is the normal allele. The 677T allele (leading to a valine substitution at amino acid 222) encodes a thermolabile enzyme with reduced activity. Individuals with two copies of 677C (677CC) have the "normal" or "wildtype" genotype. 677TT individuals (homozygous) are said to have mild MTHFR deficiency. 677CT individuals (heterozygotes) are almost the same as normal individuals because the normal MTHFR can make up for the thermolabile MTHFR .

Population prevalence: About ten percent of the North American population are T-homozygous for this polymorphism. There is ethnic variability in the frequency of the T allele - frequency in Mediterranean/Hispanics > Caucasians > Africans/African-Americans). (Source: Wikipedia: MTHFR)

A1298C SNP (Glu⁴²⁹Ala)

At nucleotide 1298 of the MTHFR, there are two possibilities: A or C. 1298A (leading to a Glu at amino acid 429) is the most common while 1298C (leading to an Ala substitution at amino acid 429) is less common. 1298AA is the "normal" homozygous, 1298AC the heterozygous, and 1298CC the homozygous for the "variant". In studies of human recombinant MTHFR, the protein encoded by 1298C cannot be distinguished from 1298A in terms of activity, thermolability, FAD release, or the protective effect of 5-methyl-THF.^[11] The C mutation does not appear to affect the MTHFR protein. It does not result in thermolabile MTHFR and does not appear to affect homocysteine levels.

Reference studies: 

1. Examining B12 Deficiency Associated With C677T Mutation on MTHFR Gene in Terms of Commonness and Endothelial Function (clinical study in progress (July 2008 - July 2010))

2. Hazra., A. et al. Common Variants of FUT2 are Associated with Plasma Vitamin B12 Levels, Nat Genet. 2008 Oct;40(10):1160-2. Epub 2008 Sep 7. (Nature Genetics paper, PubMed citation, Science Daily article)

    

1.a. DATA COLLECTION: participant genotyping data (how to find and add your data)

2. Phenotype: Vitamin B12 deficiency

C. Conclusions and Significance