rs2244012 — RAD50 RAD50 Intron 2 Variant

RAD50 Intron 2 — The Genome's Top Asthma Signal at the Th2 Cytokine Hub

The RAD50 gene¹¹ RAD50 gene
RAD50 (RAD50 double-strand break repair protein) encodes an ATPase component of the MRN complex involved in DNA damage repair — but at chromosome 5q31.1, its introns house the locus control region that coordinates IL-4, IL-5, and IL-13 expression in Th2 immune cells, making it a key regulatory scaffold for the Th2 cytokine cluster sits at one of the most replicated atopy-susceptibility loci in the human genome. At position chr5:132,565,533, rs2244012 lies within intron 2 of RAD50, 5q31.1 — a chromosomal address that genomicists have been tracking since the first genome-wide scans for IgE and asthma susceptibility. The Li et al. (2010) GWAS²² Li et al. (2010) GWAS
genome-wide association study of 473 patients with severe or difficult-to-treat asthma versus 1,892 general population controls; 292,443 SNPs genotyped; top hit rs2244012 in intron 2 of RAD50 reached P=3.04×10⁻⁷ at the 5q31 locus identified rs2244012 as the top GWAS hit at this locus — the single SNP with the strongest genome-wide association signal for asthma in the 5q31 region. The G allele tags a regulatory haplotype in the Th2 locus control region that amplifies the output of IL-4, IL-5, and IL-13 — the cytokines that collectively orchestrate allergic inflammation.

The Mechanism

The introns of RAD50 are not just splice-junction filler. A landmark study by Lee et al. (2003)³³ Lee et al. (2003)
Lee GR et al. Immunity 2003; BAC transgenic mice carrying IL4-luciferase reporters showed that a 25 kb fragment within the RAD50 gene confers Th2-specific, copy-number-dependent expression of IL-4 and IL-13 — defining this region as a locus control region (LCR) governing the adjacent Th2 cytokine gene cluster identified a 25 kb region within RAD50 as the Th2 locus control region (TH2-LCR)⁴⁴ Th2 locus control region (TH2-LCR)
a cluster of four DNase I hypersensitive sites (RHS4–RHS7) that loop chromosomally to simultaneously activate IL-4, IL-5, and IL-13 transcription when a T cell commits to the Th2 lineage; mechanistically analogous to the beta-globin LCR that governs globin gene switching during red blood cell development — a regulatory element that coordinates simultaneous transcription of IL-4, IL-5, and IL-13 when T cells commit to the Th2 lineage.

Within this control region, the rs2244012 G allele tags a haplotype that includes functional regulatory variants. One such neighbor, rs2240032 in the RHS7 element of the TH2-LCR, shows allele-specific binding of SMAD3 and SP1⁵⁵ allele-specific binding of SMAD3 and SP1
Kretschmer et al. Allergy 2014; differential transcription-factor binding at RHS7 alters methylation of the IL13 promoter and shifts IL4 and RAD50 expression in an allele-specific manner and alters DNA methylation at the IL13 promoter beginning in cord blood and persisting into childhood — a mechanism that links genotype at birth to measurable epigenetic differences in Th2 cytokine regulation years later. When this regulatory hub is in the more active state, Th2-committed T cells produce higher pulses of IL-13 and IL-4 on allergen stimulation. IL-13 then acts directly on airway epithelium and smooth muscle to drive mucus hypersecretion and airway hyperresponsiveness; IL-4 drives B-cell class switching to IgE, sensitizing mast cells to allergens systemically.

The Evidence

rs2244012 rose to the top of the 5q31 GWAS signal in the Li et al. (2010)⁶⁶ Li et al. (2010)
Li X et al. J Allergy Clin Immunol 2010; 292,443 SNPs genotyped; 473 TENOR patients with severe asthma vs 1,892 Illumina general population controls study — the first large-scale GWAS to genotype the RAD50-IL13 region at the density needed to resolve the 5q31 signal. Multiple SNPs in the region reached significance, but rs2244012 carried the strongest p-value at P=3.04×10⁻⁷, implicating intron 2 of RAD50 as the locus index variant for asthma in this cohort.

Fine-mapping by Sharma et al. (2014)⁷⁷ Sharma et al. (2014)
Sharma V et al. Allergy 2014; 64 polymorphisms across three IgE loci (1q23, 5q31, 12q13) in >1,300 German children; 5q31 confirmed as a major IgE determinant; risk alleles at all three loci together elevate IgE risk fourfold in more than 1,300 German children confirmed 5q31 (RAD50-IL13 and IL4) as one of three major determinants of total serum IgE. Associations at this locus are primarily with mild-to-moderate IgE elevation — the 5q31 signal reflects a common population-level Th2 amplifier rather than a rare high-penetrance risk factor.

The atopic spectrum of this locus extends beyond asthma. The 5q31.1 region maps to the IL4/KIF3A locus in a meta-analysis by Marenholz et al. (2015)⁸⁸ meta-analysis by Marenholz et al. (2015)
Nature Commun 2015; 12 populations, 2,428 cases of infantile eczema progressing to childhood asthma, 17,034 controls; seven genome-wide significant loci for the atopic march identified; IL4/KIF3A at 5q31.1 confirmed identifying seven loci for the atopic march — the progression from eczema to food allergy to asthma to allergic rhinitis — confirming that the 5q31 signal drives not just asthma risk but the full sequential atopic phenotype.

Replication has been mixed by population: the Li et al. finding was replicated in Pakistani children (Ghani et al. 2025, PMID 41001556), while a Han Chinese pediatric study (Li et al. 2016, PMID 26365633) found no association — population-specific genetic backgrounds and differing LD structures likely explain the discrepancy. The G allele shows dramatically higher frequency in African ancestry (~61%) compared to European (~22%) and East Asian (~18%) populations, consistent with a common regulatory haplotype that is ancestrally enriched in African populations.

Practical Implications

The G allele at rs2244012 lowers the threshold at which allergen exposure triggers sensitization and sustained allergic inflammation. The mechanism is upstream Th2 cytokine amplification — each G allele shifts the IL-13/IL-4 output capacity of Th2 cells upward, raising baseline IgE and making mast cell sensitization faster and more durable. Children carrying the G allele who develop early eczema face elevated biological risk for the full atopic march; adults who have never developed overt atopy may still carry subclinically elevated IgE that sensitizes them to new occupational or environmental allergens more readily than AA individuals.

Therapeutically, the biology is increasingly tractable: dupilumab (anti-IL-4Rα, blocking both IL-4 and IL-13), tralokinumab (anti-IL-13), and cendakimab (anti-IL-13Rα1) directly counter the cytokine output amplified by this genotype. G allele carriers with refractory atopic disease are biologically well-matched to this drug class.

Interactions

rs2244012 lies within the same 5q31.1 RAD50/TH2-LCR haplotype block as rs2040704 and rs2240032 — these variants are in strong linkage disequilibrium and collectively tag the Th2 locus control region regulatory haplotype. The rs2040704 G allele at the TH2-LCR enhancer hub and rs2244012 G allele in RAD50 intron 2 likely co-segregate on the same risk haplotype, making their combined effect equivalent to carrying a single high-activity TH2-LCR configuration.

Carriers who also carry rs20541-A (IL13 R130Q, increased IL-13 bioavailability) face a double hit: elevated IL-13 production from this locus control region variant, combined with reduced IL-13 decoy receptor clearance from the downstream coding variant. The combination of rs1801275 (IL-4Rα R576Q) with the G allele at this locus creates a production × receptor synergy that is particularly relevant to dupilumab pharmacogenomics.