rs71625130 — SNX27 1q21.3 T-cell signaling / Th17 locus variant

Intronic SNX27 variant at the 1q21.3 GWAS locus that increases atopic dermatitis risk; the locus also encompasses nearby RORC, the master Th17 transcription factor

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SNX27 rs71625130 — The T-Cell Synapse Variant at the Heart of Atopic Inflammation

Atopic dermatitis (eczema) is the most common chronic inflammatory skin disease, driven by an immune system that responds inappropriately to harmless environmental triggers. One of its key drivers is T-helper cell dysregulation11 T-helper cell dysregulation
T helper cells coordinate immune responses by releasing cytokines; subtypes Th2, Th17, and Th22 all contribute to eczema flares through different inflammatory signals, particularly an imbalance that tips immune activation too far toward inflammation. The rs71625130 variant sits at a genetic locus — chromosome 1q21.3 — that has emerged as one of the most statistically robust atopic dermatitis risk signals ever identified, with an association p-value of 2×10⁻⁸⁹.

The SNP lies within an intron of SNX27 (Sorting Nexin 27), a scaffolding protein that governs how signalling molecules are trafficked within T cells. The 1q21.3 locus also harbours RORC approximately 150 kb downstream — the gene encoding RORγt22 RORγt
RAR-related orphan receptor gamma-t; the master transcription factor that drives Th17 cell differentiation and IL-17 production — making this a biologically coherent stretch of immune regulation DNA.

The Mechanism

SNX27 operates at the immune synapse33 immune synapse
The organised interface formed between a T cell and an antigen-presenting cell; SNX27 localises here in an activation-dependent manner to regulate signalling kinetics — the contact zone where T cells recognise foreign antigens and decide whether to mount an immune response. SNX27's PDZ domain physically escorts diacylglycerol kinase ζ (DGKζ)44 diacylglycerol kinase ζ (DGKζ)
An enzyme that phosphorylates the second messenger diacylglycerol (DAG), reducing its concentration and dampening downstream TCR signalling through PKC and Ras/ERK pathways back to the membrane. This acts as a tuning mechanism: SNX27 limits how strongly a T cell fires.

Beyond DGKζ recycling, SNX27 directly controls the abundance of Lck and CD455 Lck and CD4
Lck is the tyrosine kinase that phosphorylates the T cell receptor complex; CD4 is the co-receptor that stabilises and amplifies the TCR signal. Together they set the threshold for T cell activation at the cell surface. When SNX27 expression is reduced, CD4 and Lck levels fall in resting T cells, yet paradoxically the cells become hyperresponsive: NF-κB activity rises, CXCR4 is upregulated, and lytic enzymes and proinflammatory cytokines pour out. The result is a T cell that activates too easily and produces too much inflammation.

The Evidence

The key evidence comes from the largest atopic dermatitis GWAS conducted to date. Budu-Aggrey et al. 202366 Budu-Aggrey et al. 2023
European and multi-ancestry genome-wide association meta-analysis; discovery cohort 1,086,394 individuals; replication cohort 3,604,027 individuals — by far the largest AD genetic study identified 81 loci in Europeans (29 novel) and 10 additional multi-ancestry loci, with rs71625130-A emerging as one of the strongest signals at OR=1.17 and an extraordinary p-value of 2×10⁻⁸⁹. The A allele frequency of ~4% in Europeans means it is carried heterozygously by roughly 1 in 15 Europeans — a meaningful population burden for such a strong effect.

The biological plausibility rests on independent functional studies. Martinez-Martin et al. 202477 Martinez-Martin et al. 2024
Nat Commun; demonstrated SNX27 regulation of Lck/CD4 at the T cell immune synapse and downstream proinflammatory consequences of SNX27 loss showed that impaired SNX27 expression contributes directly to CD4 T cell dysfunction with inflammatory features consistent with atopic disease. Cosen-Binker et al. 201788 Cosen-Binker et al. 2017
J Immunol; showed SNX27-DGKζ axis controls TCR signalling amplitude and T cell metabolic programming established the mechanistic link between SNX27, signal calibration, and the transcriptional programmes that determine whether a T cell triggers inflammation.

Practical Actions

Carriers of the A allele have increased lifetime susceptibility to atopic dermatitis. The variant's effect is additive, so heterozygous carriers (AG) have one dose of risk and homozygous carriers (AA) — extremely rare, under 0.05% — carry two.

Monitoring atopic disease activity is relevant for carriers.

Genotype Interpretations

What each possible genotype means for this variant.

GG Non-carrier Normal

No increased atopic dermatitis risk from this locus

You carry two copies of the common G allele at rs71625130. About 96% of people globally share this genotype.

AG Single-copy carrier Intermediate

One copy of the atopic dermatitis risk allele — moderately elevated Th17 susceptibility

The SNX27 protein calibrates T cell activation by recycling DGKζ and controlling CD4/Lck abundance at the immune synapse. Reduced SNX27 expression leads to heightened NF-κB activity and proinflammatory cytokine output, consistent with the atopic dermatitis association. The 1q21.3 locus also encompasses RORC ~150 kb downstream — the master transcription factor for Th17 cell differentiation — so regulatory effects on both genes may contribute to the atopic risk signal.

AA Two-copy carrier High Risk

Two copies of the atopic dermatitis risk allele — substantially elevated Th17 inflammatory susceptibility

Additive genetics predicts a risk approximately equivalent to two doses of the OR=1.17 per-allele effect, yielding an estimated OR around 1.37 relative to GG carriers. The extreme rarity of this genotype (predicted ~1 in 2,000 Europeans) means clinical data specifically on AA homozygotes are limited, but the additive model is well-supported by GWAS data for this variant class.