Genetics of Methylation
Methylation is a fundamental biochemical process supporting DNA repair, neurotransmitter synthesis, detoxification, and gene expression regulation. MTHFR and related gene variants are among the most commonly discussed genetic variants in chronic illness communities.
This page is for educational and informational purposes only. Not a diagnostic tool. Always consult a qualified healthcare provider.
What is Methylation?
Methylation refers to the transfer of methyl groups in biochemical reactions — a process central to one-carbon metabolism, DNA methylation, and the synthesis of key molecules including SAM (S-adenosylmethionine), glutathione, and neurotransmitters. The folate and methionine cycles are the primary methylation pathways, with MTHFR (methylenetetrahydrofolate reductase) playing a key regulatory role. Variants reducing MTHFR activity — particularly C677T (rs1801133) — are present in approximately 10% of the population as homozygotes and affect homocysteine metabolism, folate availability, and downstream methylation capacity.
Biological pathways commonly discussed in relation to Methylation
Research into Methylation and One-Carbon Metabolism has highlighted several biological pathways that may be relevant. Genetic variants within these pathways may influence individual susceptibility, symptom severity, or the trajectory of the condition.
Folate Cycle
The folate cycle processes dietary folate into 5-MTHF, the active form used by MTHFR to support methionine synthesis. Variants in MTHFR, FOLR1, and DHFR affect folate processing efficiency.
Methionine Cycle
The methionine cycle produces SAM, the universal methyl donor. TCN2, MTR, MTRR, and BHMT variants affect methionine cycle efficiency and SAM availability.
Homocysteine Metabolism
Homocysteine is a metabolic intermediate that must be remethylated or transsulfurated. Elevated homocysteine (from impaired MTHFR or B12/folate deficiency) is associated with cardiovascular and neurological risk.
Dna Methylation
SAM-dependent DNA methylation regulates gene expression epigenetically. Impaired methylation capacity may affect gene expression patterns relevant to immune function, inflammation, and neurotransmitter synthesis.
Key genes studied in relation to Methylation
The following genes have been studied in relation to Methylation and One-Carbon Metabolism. These genes span the biological pathways most commonly discussed in this area of research.
12 genes total studied in relation to Methylation across the ChronicDNA dataset.
Genetic variants commonly discussed
The following genetic variants (SNPs) are found in genes that have been studied in relation to Methylation. Each variant represents a position in the genome where individuals may carry different alleles.
15 variants total across genes studied in relation to Methylation.
How personal DNA data may provide educational insights
Consumer DNA files from 23andMe, AncestryDNA, and MyHeritage contain raw SNP data. When you upload your file to ChronicDNA, the analysis engine checks your genotype against a curated panel of 80+ genes selected for their relevance to Long COVID, ME/CFS, and connected biological pathways - some of which may relate to areas such as Methylation.
This is not a diagnostic service. Genetic variants do not determine whether you have Methylation, nor do they predict your clinical outcomes. The report is educational - it explains which variants you carry, what the research says about them, and how they fit into the biological pathways most relevant to chronic illness. All results should be discussed with a qualified healthcare provider.
Related conditions and pathways
Methylation shares biological pathways and genetic associations with the following related conditions and areas of research.
Frequently asked questions
What is MTHFR and why is it discussed in chronic illness?
MTHFR encodes an enzyme central to folate and methylation metabolism. The C677T variant (rs1801133) reduces enzyme activity by approximately 70% in homozygotes, affecting folate processing, homocysteine levels, and downstream methylation capacity. It is one of the most discussed variants in Long COVID and ME/CFS communities.
Does MTHFR cause ME/CFS or Long COVID?
No. MTHFR variants do not cause ME/CFS or Long COVID. They may influence methylation capacity, homocysteine levels, and certain metabolic pathways that could contribute to symptom expression in the context of chronic illness — but they are common variants found in healthy individuals worldwide.
Which methylation genes are most studied?
Key genes include MTHFR, MTR, MTRR, BHMT, TCN2, FOLR1, DHFR, and COMT. These cover the folate cycle, methionine cycle, and homocysteine metabolism.
What does 'compound heterozygous MTHFR' mean?
Compound heterozygous MTHFR refers to carrying one C677T variant and one A1298C variant (rs1801131) on different chromosomes. This combination partially reduces MTHFR activity and is often discussed in functional medicine contexts, though its clinical significance is debated in mainstream medicine.
Explore DNA insights
If you already have DNA data from 23andMe, AncestryDNA, or MyHeritage, upload your raw file to ChronicDNA and receive a personalised educational report covering genes studied in relation to Methylation and connected biological pathways.
Get Your Personalised DNA ReportInformational and educational only · Not a diagnostic tool · GDPR compliant
12 genes · 15 variants analysed in relation to Methylation