Gene–environment interaction modulated by allelic heterogeneity in inflammatory diseases

TLDR

CARD15 is a major susceptibility gene for Crohn disease, a common multifactorial inflammatory bowel disorder. NF‑κB activation assays revealed that CARD15 detects bacterial peptidoglycan, but CD‑associated variants impair this response, while Blau’s syndrome alleles trigger PGN‑independent activation, and the quantitative response predicted diverse CD manifestations.

Abstract

CARD15 is a major susceptibility gene for a frequent multifactorial chronic inflammatory bowel disorder, Crohn disease (CD). By using NF-κB activation assays, the cytosolic CARD15 was shown to efficiently detect bacterial peptidoglycan (PGN), reminiscent of the PGN recognition protein surveillance mechanism in Drosophila . The 3 CD-associated variants and 13 additional variants carried by CD patients demonstrated impaired PGN-dependent response revealing null, hypomorphic, or dominant-negative properties. Quantitative parametrization of this response, computed from the patients' CARD15 genotypes, was predictive of several variable CD manifestations. In contrast, CARD15 alleles associated with Blau's syndrome promoted PGN-independent NF-κB activation, an observation that accounts for the minimal microbial input in the etiology of this dominant, monogenic inflammatory disorder affecting solely aseptic sites.