Defects in NADPH Oxidase Genes and in Very Early Onset Inflammatory Bowel Disease.

BACKGROUND & AIMS: Defects in intestinal innate defense systems predispose patients to inflammatory bowel disease (IBD). Reactive oxygen species (ROS) generated by nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases in the mucosal barrier maintain gut homeostasis and defend against pathogenic attack. We hypothesized that molecular genetic defects in intestinal NADPH oxidases might be present in children with IBD.

METHODS

After targeted exome sequencing of epithelial NADPH oxidases and on 209 children with very early onset inflammatory bowel disease (VEOIBD), the identified mutations were validated using Sanger Sequencing. A structural analysis of and variants was performed by homology in silico modeling. The functional characterization included ROS generation in model cell lines and in in vivo transduced murine crypts, protein expression, intracellular localization, and cell-based infection studies with the enteric pathogens and enteropathogenic .

RESULTS

We identified missense mutations in (c.988G>A, p.Pro330Ser; c.967G>A, p.Asp360Asn) and (c.4474G>A, p.Arg1211Cys; c.3631C>T, p.Arg1492Cys) in 5 of 209 VEOIBD patients. The p.Asp360Asn variant was replicated in a male Ashkenazi Jewish ulcerative colitis cohort. All and variants showed reduced ROS production compared with wild-type enzymes. Despite appropriate cellular localization and comparable pathogen-stimulated translocation of altered oxidases, cells harboring or variants had defective host resistance to infection with .

CONCLUSIONS

This study identifies the first inactivating missense variants in and associated with VEOIBD. Defective ROS production from intestinal epithelial cells constitutes a risk factor for developing VEOIBD.