rs11229030 — PRG2

PRG2 — When Eosinophil Granule Proteins Attack the Gut

Inside your gastrointestinal tract, a normally protective immune cell may be working against you. Eosinophils — immune cells best known for fighting parasites and driving allergic reactions — reside in the gut wall as part of normal tissue defense. When activated, they discharge their granule contents, including major basic protein (MBP)¹¹ major basic protein (MBP)
The predominant crystalline core protein of eosinophil granules, encoded by the PRG2 gene on chromosome 11q12.1. MBP is a cationic protein that disrupts cell membranes through electrostatic interaction, causing cytotoxicity to host epithelial cells when released in excess. rs11229030 sits in the PRG2/PRG3 gene cluster — two closely related eosinophil major basic protein genes — and its C allele was identified as a Crohn's disease susceptibility signal in a large genome-wide association study of Ashkenazi Jewish populations.

The Mechanism

PRG2 encodes eosinophil major basic protein (MBP), the predominant constituent of the crystalline core of the eosinophil granule. When eosinophils degranulate in the gut wall, MBP directly increases epithelial layer permeability²² epithelial layer permeability
MBP disrupts cell membrane integrity through its highly cationic charge, causing direct toxicity to epithelial cells and increasing paracellular permeability — the same "leaky gut" mechanism central to Crohn's disease pathophysiology. Mouse studies confirm the causal link: MBP knockout mice are protected from experimental colitis, and in vitro co-culture of eosinophils with intestinal epithelial cells causes dose-dependent epithelial dysfunction attributable to MBP.

rs11229030 at chr11:57,435,536 (GRCh38) lies approximately 45 kb downstream of PRG2 (chr11:57,386,780–57,390,650) and within the broader PRG2/PRG3 regulatory neighborhood. The SNP's intergenic location suggests it acts as a regulatory tag SNP influencing expression levels in this eosinophil protein cluster rather than altering protein sequence directly. The neighboring PRG3 gene encodes a related eosinophil major basic protein homologue (MBPH), also expressed preferentially in eosinophils, providing two potential effectors at this locus.

The Evidence

The association between rs11229030 and Crohn's disease emerged from a genome-wide scan combining 10 Ashkenazi Jewish cohorts³³ genome-wide scan combining 10 Ashkenazi Jewish cohorts
Ashkenazi Jews have a 2–4× higher prevalence of Crohn's disease than non-Jewish Europeans, making this population particularly informative for discovering CD susceptibility loci: 907 cases and 2,345 controls in discovery, followed by 971 cases and 2,124 controls in replication. rs11229030 reached genome-wide significance (OR 1.15, p=8×10⁻⁹), ranking among five novel loci identified in the study. While an OR of 1.15 represents a modest per-allele effect — typical for common GWAS variants in complex diseases — the biological candidacy of PRG2/PRG3 at this locus provides strong mechanistic plausibility.

Evidence for eosinophil-mediated intestinal damage in Crohn's disease is well established independently. Ultrastructural studies show eosinophil MBP granule release and cytotoxic tissue changes specifically in Crohn's disease biopsy specimens. Eosinophil cationic protein (ECP), a related granule protein, correlates with Crohn's disease activity with remarkable precision⁴⁴ activity with remarkable precision
r=0.89, p<0.0001 in 10 children with Crohn's disease followed prospectively; active disease median ECP 24.5 µg/L vs remission 5.7 µg/L. And in patients with Crohn's disease, elevated eosinophilic infiltration is associated with fibrosis development and poor response to medical therapy.

Practical Actions

For CC genotype carriers, the actionable implications center on gut barrier support and early monitoring. Eosinophil-driven permeability is worsened by food antigens that trigger eosinophil degranulation; eliminating common triggers can reduce intestinal eosinophil activation. Monitoring stool calprotectin and blood eosinophil counts provides early warning of inflammatory flares before clinical symptoms escalate. In established Crohn's disease, serum ECP can be used as a disease-activity index alongside standard markers.

Interactions

The PRG2 locus operates within the broader landscape of Crohn's disease genetic risk. Variants in rs7234029 (PTPN2) reduce T-cell regulatory phosphatase activity, lowering the threshold for immune activation that drives eosinophil recruitment. The rs2631367 variant in SLC22A5 (OCTN2) impairs carnitine transport in intestinal epithelial cells, compounding the barrier dysfunction that eosinophil MBP degranulation initiates. Carriers of multiple Crohn's disease risk alleles — particularly those affecting both eosinophil effector function (PRG2) and immune activation thresholds (PTPN2, IL23R) — face additive susceptibility. Each of these interactions involves independent biological mechanisms that converge on intestinal barrier disruption and aberrant immune activation.