OP33 CGNL1 in very early onset IBD

Abstract Background In a patient with very early onset (VED)-IBD, we identified new pathogenic mutations in CGNL1, which encodes a junctional protein with unknown function in GI disease. Methods Whole exome sequencing (WES) was performed on the patient with VEO-IBD and all first-degree relatives with IBD and other inflammatory disease. Intestinal organoids from the patient and controls were characterized by transepithelial electrical resistance (TEER), FITC-dextran permeability assay, immunofluorescence (IF), RNA-seq, and transmission electron microscopy (TEM). We generated a new Cgnl1-/- mouse model, which was characterized using above assays as well as colitis and infection models, 16S rRNA-seq, etc. Evans blue assay and TEM were also performed to evaluate intestinal vascular integrity in mice. Organoids and mice were treated by chemical chaperones TUDCA and 4-PBA to reduce endoplasmic reticulum (ER) stress, a pathogenic pathway in IBD. Results In the affected patient with VEO-IBD who required early total colectomy and pouch formation with coexistent primary sclerosing cholangitis (PSC) and celiac disease, WES identified two rare, pathogenic variants in CGNL1. Both variants are also present in the patient’s sister with a similar history of early onset IBD and hepatobiliary disease. CGNL1 protein diminished in patient’s intestinal epithelium and is associated with spontaneous ER stress. Patient organoids form smaller 3D spheroids with altered cell composition, skewed microvilli, impaired junctional complexes, and reduced barrier function which was rescued by chemical chaperone (Fig 1). Similarly, we observed shortened microvilli, disrupted junctional complexes, enhanced epithelial ER stress, and increased gut permeability in Cgnl1-/- mice. At steady state, Cgnl1-/- mice show a new Paneth-like IEC in the colon, elevated fecal marker of inflammation, and altered gut microbiome (not shown). Cgnl1-/- mice exhibit substantial vulnerability to DSS-induced colitis and C. difficile infection. Chemical chaperone was sufficient to alleviate ER stress and restore epithelial barrier integrity in Cgnl1-/- mice at steady state and with colitis or infection (Fig 2). Similar to the epithelium, intestinal vasculature of Cgnl1-/- mice exhibit disrupted junctional complexes and augmented permeability (not shown). Conclusion Loss-of-function CGNL1 variants contribute to VEO-IBD by disrupting gut barrier integrity and activating epithelial ER stress in patient organoids and mouse models. This study expands our understanding of epithelial barrier impairment in VEO-IBD and highlights intestinal epithelium as a therapeutic target. Chemical chaperones as novel therapies for IBD caused by primary intestinal barrier defects warrant further investigations. Conflict of interest: Ma, Kaiming: No conflict of interest Zhu, Echo: No conflict of interest Yao, Xin: No conflict of interest Deepak, Parakkal: Grant: Johnson and Johnson, AbbVie, Takeda Pharmaceuticals, Prometheus Biosciences, Teva Pharmaceuticals, Sanofi, Merck, ExeGI Pharmaceuticals, Agomab, Tr1X, Direct Biologics, Astra Zeneca and Eli Lilly. Personal Fees: Johnson and Johnson, CorEvitas LLC, Eli Lilly, Sobi Ciorba, Matthew: No conflict of interest Cao, Siyan: No conflict of interest