rs953413 — ELOVL2

ELOVL2 rs953413 — The Enhancer Switch for DHA Synthesis

The conversion of dietary plant omega-3s into DHA — the brain's dominant structural fat — is governed by a chain of enzymes whose efficiency varies widely between individuals. ELOVL2 (elongase of very long chain fatty acids protein 2) catalyzes the critical elongation step that converts EPA (20:5) into DPA (22:5) and then toward DHA (22:6). The rs953413 variant, sitting in the first intron of ELOVL2, controls how much of this enzyme the liver makes. Unlike many GWAS variants whose functional mechanism remains unknown, rs953413 has a precisely characterized molecular role: it sits inside a cooperative enhancer element¹¹ cooperative enhancer element
A regulatory DNA sequence that increases transcription of a nearby gene when transcription factors bind to it that is bound by the liver transcription factors FOXA1/FOXA2 and HNF4α²² FOXA1/FOXA2 and HNF4α
Hepatocyte nuclear factors — master regulators of liver gene expression that coordinate fatty acid, glucose, and bile acid metabolism.

The Mechanism

Pan and colleagues³³ Pan and colleagues
Pan G et al. rs953413 Regulates Polyunsaturated Fatty Acid Metabolism by Modulating ELOVL2 Expression. iScience, 2020 used luciferase reporter assays, ChIP-qPCR, and CRISPR/Cas9 editing in hepatic cell lines to show that the G allele of rs953413 preferentially recruits FOXA1, FOXA2, and HNF4α to an evolutionarily conserved intronic enhancer. This allele-specific transcription factor binding upregulates ELOVL2 expression. The A allele disrupts this binding, reducing ELOVL2 transcription. FOXA knockdown and direct Cas9 mutation of the enhancer both significantly downregulated ELOVL2 expression (p < 0.01), confirming the causal chain from SNP → transcription factor binding → ELOVL2 expression → LC-PUFA levels.

The downstream consequence is that A-allele carriers produce less ELOVL2 enzyme, slowing the EPA→DPA→DHA elongation cascade in the liver. This creates a phenotype with characteristically lower baseline DHA but paradoxically greater responsiveness to preformed omega-3 supplementation — a pattern seen across multiple independent intervention trials.

The Evidence

rs953413 was the lead variant in the original InCHIANTI GWAS⁴⁴ InCHIANTI GWAS
Tanaka T et al. Genome-wide association study of plasma polyunsaturated fatty acids in the InCHIANTI Study. PLoS Genet, 2009 of 1,075 Italian adults, where it reached p = 1.1×10⁻⁶ for plasma EPA — establishing ELOVL2 as a major genetic determinant of omega-3 fatty acid levels in humans. The signal replicated in 1,076 GOLDN study participants, where ELOVL2 variants were associated with DPA and DHA levels.

The most striking clinical data comes from an exploratory supplementation trial by Metherel and colleagues⁵⁵ Metherel and colleagues
Metherel AH et al. Higher Increase in Plasma DHA in Females Compared to Males Following EPA Supplementation May Be Influenced by a Polymorphism in ELOVL2: An Exploratory Study. Lipids, 2021. Young adults (n = 14–15 per group) received 3 g/day EPA for 12 weeks. Overall, females showed substantially greater plasma DHA increases than males (+23.8 vs. −13.8 nmol/mL; p < 0.01). When stratified by rs953413 genotype, the effect was dramatic: AA-genotype females gained +58.8 ± 11.5 nmol/mL DHA, compared to +4.34 ± 13.5 nmol/mL for GA+GG females and −29.1 ± 17.2 nmol/mL for AA males (p < 0.001). This sex × genotype interaction suggests that estrogen-mediated upregulation of the EPA→DHA elongation pathway partially compensates for the low-ELOVL2 A-allele phenotype in females, while AA-genotype males face the full deficit.

The Alsaleh 2014 fish oil trial⁶⁶ Alsaleh 2014 fish oil trial
Alsaleh A et al. ELOVL2 gene polymorphisms are associated with increases in plasma EPA and DHA proportions after fish oil supplement. Genes Nutr, 2014 of 367 subjects confirmed that ELOVL2 minor-allele carriers — across rs953413, rs2236212, and rs3734398 — showed approximately 30% higher plasma EPA and 9% higher DHA after 1.8 g/day fish oil supplementation (p = 0.002–0.017), reinforcing that preformed omega-3 supply strongly compensates for reduced endogenous elongation.

A notable additional dimension of this locus is its role in epigenetic aging⁷⁷ epigenetic aging
DNA methylation changes that accumulate with age and can be used to predict biological age independently of chronological age. Garagnani and colleagues⁸⁸ Garagnani and colleagues
Garagnani P et al. Methylation of ELOVL2 gene as a new epigenetic marker of age. Aging Cell, 2012 demonstrated that CpG island methylation in the ELOVL2 promoter/enhancer region correlates with chronological age at r = 0.92 across 501 subjects aged 9–99 years. The rs953413 variant sits within precisely this regulatory region. Whether the SNP's effect on transcription factor binding modulates the rate of age-associated methylation accumulation remains an open research question, but the overlap establishes this locus as a convergence point for fatty acid metabolism and biological aging biology.

Practical Implications

For AA-genotype individuals, the key implications are: (1) endogenous DHA synthesis from plant-derived ALA or EPA is constrained by reduced ELOVL2 activity; (2) preformed DHA supplementation bypasses this bottleneck and is well-supported by multiple intervention studies; (3) males with AA are at greater deficit than females because estrogen-mediated elongation partially compensates in women. Fish oil or algae-based DHA at 1–2 g/day is the most direct intervention, with the omega-3 index as the objective measure of adequacy.

Interactions

rs953413 is in partial linkage disequilibrium with rs2236212 in European populations, and both variants affect ELOVL2 activity through different mechanisms: rs2236212 is associated with reduced enzymatic elongation activity (Maguolo et al. 2021), while rs953413 acts upstream by controlling transcription factor binding and ELOVL2 gene expression. Carrying risk alleles at both loci may compound the reduction in DHA synthesis capacity. Upstream in the same pathway, FADS1/FADS2 variants (rs174547, rs174537) affect the desaturation of ALA to EPA — individuals with both FADS low-activity and ELOVL2 low-expression genotypes face impairment at two sequential steps, making plant-based omega-3 strategies essentially ineffective and preformed marine DHA the only reliable route to adequate status.