rs2546890 — LOC285626 LOC285626 rs2546890

LOC285626 rs2546890 — IL12B Regulatory Variant and Multi-Disease Autoimmune Risk

The rs2546890 variant sits approximately 2,000 base pairs upstream of the IL12B gene¹¹ IL12B gene
located at chromosome 5q33.3, encodes the p40 subunit shared by interleukin-12 and interleukin-23, within a non-coding RNA locus designated LOC285626. IL-12 and IL-23 are cytokines produced by dendritic cells and macrophages that act as master switches for adaptive immune responses: IL-12 drives naive T cells toward the Th1 (IFN-γ-producing) lineage, while IL-23 sustains the Th17 (IL-17-producing) lineage. Both arms are implicated in autoimmune demyelination, psoriatic inflammation, and immune-mediated liver disease. The rs2546890 A allele has been associated in large genome-wide studies with elevated risk of multiple sclerosis, psoriasis, and primary biliary cholangitis — three immunologically distinct diseases unified by shared IL-12/IL-23 pathway dysregulation.

The Mechanism

rs2546890 is annotated as a non-coding transcript variant in the LOC285626 locus. Its position in the IL12B upstream regulatory region places it within a genomic neighborhood that contains multiple independently replicated autoimmune susceptibility signals. The IL12B locus at 5q33.3 harbors several GWAS-identified variants (including rs6887695 in the upstream region and rs3212227 in the 3′ UTR) that form a risk haplotype functionally linked to elevated p40 subunit expression in monocytes and dendritic cells. Carriers of the IL12B risk haplotype show increased IL12B mRNA and protein in antigen-presenting cells, leading to higher serum IL-12 and a Th1-polarized immune milieu²² increased IL12B mRNA and protein in antigen-presenting cells, leading to higher serum IL-12 and a Th1-polarized immune milieu
The p40 subunit is shared by both IL-12 and IL-23 heterodimers, so expression changes affect both cytokine outputs simultaneously. rs2546890 is in linkage disequilibrium with variants in this regulatory haplotype, likely tagging the same functional effect — enhanced transcription factor access to the IL12B promoter region during innate immune activation.

The Evidence

The association of rs2546890 with multiple sclerosis has been established across multiple large GWAS cohorts. The 2011 International MS Genetics Consortium (IMSGC) study³³ 2011 International MS Genetics Consortium (IMSGC) study
Sawcer et al., Nature 2011, PMID 21833088 analysed 9,772 MS cases and 16,849 controls of European ancestry across 23 research groups and identified the IL12B locus region among at least 29 novel susceptibility signals. The 2019 IMSGC genomic map⁴⁴ 2019 IMSGC genomic map
International MS Genetics Consortium, Science 2019, PMID 31604244 expanded this to 47,429 MS cases and 68,374 controls, confirming rs2546890 among 200 autosomal susceptibility variants, with an odds ratio of approximately 1.11 (p = 1×10⁻¹¹). An independent Italian cohort study Leone et al., PLOS ONE 2013, PMID 23785401⁵⁵ Leone et al., PLOS ONE 2013, PMID 23785401 found that rs2546890 near IL12B was the only non-HLA variant significantly associated with cerebrospinal fluid oligoclonal bands — a biomarker of CNS-compartmentalised inflammation — in 1,115 Italian MS patients (OR 1.45, 95% CI 1.09–1.92), validated by in silico replication in Scandinavian and Belgian cohorts.

For psoriasis, the IL12B locus is one of the most robustly replicated susceptibility signals. GWAS Catalog records for rs2546890 show associations at p = 1×10⁻²⁰ (OR 1.54, 95% CI 1.32–1.79) and p = 3×10⁻³⁵ (OR 1.39, 95% CI 1.32–1.47) across separate European cohorts. Pharmacogenomic studies link rs2546890 to biologic treatment response: Ovejero-Benito et al., Pharmacogenomics 2017, PMID 28470127⁶⁶ Ovejero-Benito et al., Pharmacogenomics 2017, PMID 28470127 found association with etanercept response at 6 months (n=68), and the same group Pharmacogenomics 2018, PMID 29192552⁷⁷ Pharmacogenomics 2018, PMID 29192552 found that rs2546890 was among five SNPs associated with PASI75 response to adalimumab or infliximab at 3 months (n=95). For primary biliary cholangitis, an international GWAS meta-analysis Cordell et al., 2015, PMID 26394269⁸⁸ Cordell et al., 2015, PMID 26394269 identified the locus at p = 5×10⁻¹² (beta = 0.133). The convergence of three immunologically distinct conditions on the same variant underscores its role as a broad immune-regulatory signal rather than a disease-specific variant.

Practical Actions

For individuals carrying one or two A alleles, the primary actionable implications are: (1) heightened monitoring for early signs of MS, psoriasis, and autoimmune liver disease; (2) awareness of the pharmacogenomic relevance to IL-12/IL-23 pathway-targeting biologics. Ustekinumab (Stelara) targets the p40 subunit encoded by IL12B — the protein whose expression is amplified by the risk haplotype this variant tags. Pharmacogenomic studies show that IL12B genotype influences ustekinumab response in psoriasis, making this result clinically relevant for biologic selection. Similarly, IL-12/IL-23 pathway-blocking biologics used in MS (natalizumab does not target this pathway directly, but newer agents such as ofatumumab act upstream in the B-cell/innate immune cascade implicated by this locus) are of increasing relevance.

Interactions

rs2546890 acts within the broader IL12B susceptibility haplotype that includes rs6887695 (upstream) and rs3212227 (3′ UTR). Individuals carrying risk alleles at rs2546890 alongside the IL12B 3′ UTR risk haplotype (rs3212227) likely have compounding effects on p40 expression. The IL23R rs11209026 (R381Q) loss-of-function variant provides strong protection against MS, psoriasis, IBD, and ankylosing spondylitis by reducing IL-23 receptor signaling downstream of the p40-containing IL-23 heterodimer. Carrying both the rs2546890 A risk allele (elevated IL12B expression) and the IL23R rs11209026 protective A allele creates a partial antagonistic interaction that would benefit from compound action analysis. The existing IL12B SNP rs12188300 in GeneOps operates on a partially overlapping locus; individuals carrying risk alleles at both rs12188300 and rs2546890 likely have additive effects on IL-12/IL-23 pathway amplification.