rs1801131, often called A1298C, is a single‑nucleotide polymorphism in the MTHFR gene that results in an amino‑acid change in the encoded enzyme (commonly noted as Glu429Ala). MTHFR (methylenetetrahydrofolate reductase) is a key enzyme that reduces 5,10‑methylene‑tetrahydrofolate to 5‑methyl‑THF, the primary form of folate used for remethylation of homocysteine to methionine. This variant was identified in population genetic studies and is commonly evaluated alongside the C677T MTHFR variant. Research shows rs1801131 can be associated with modest changes in enzyme activity depending on genotype; its clinical relevance is best assessed together with biochemical markers like folate, B12, and homocysteine rather than in isolation.

Genetic patterns suggestive of relatively higher or typical MTHFR activity (for example, absence of the 1298 variant) are associated with standard conversion of folate to 5‑methyl‑THF, which supports normal methylation capacity in the presence of adequate nutrients. In contrast, genotypes that include one or two copies of the 1298 C allele are often described as linked to reduced MTHFR activity; this pattern may be associated with lower availability of 5‑methyl‑THF and, under certain nutritional contexts, higher homocysteine levels. Interpretation requires the full Foundation Zoomer picture: folate, B12, homocysteine, and related markers determine whether a genotype pattern is clinically meaningful for an individual. Variant presence alone does not specify current folate status or methylation health without those biochemical data.

This marker is included in the Foundation Zoomer methylation genetics panel to clarify how an individual’s MTHFR genotype may influence folate processing, homocysteine handling, and broader methylation patterns. Combined with nutrient and metabolic results, it helps providers interpret system‑level patterns and prioritize targeted follow‑up testing or monitoring.