Study of susceptibility factors, modification and prognosis in the development of Hirschsprung’s disease-associated enterocolitis via omics analysis of data from whole-exome sequencing studies, genome-wide association studies and proteomics.

Hirschsprung’s disease (HSCR) is a congenital gut malformation caused by a lack of innervation. One of the most serious is HSCR associated enterocolitis (HAEC), a potentially lethal condition with 30% of incidence. However, the causes of HAEC are still unknown and the onset is difficult to predict. This thesis work focuses on the study of susceptibility factors, modifications, and prognosis in the development of Hirschsprung’s (HSCR) disease-associated enterocolitis (HAEC) using different omics technologies. Genetic Investigation of HAEC by Whole-Exome Sequencing (WES) on 24 HSCR patients affected (HAEC) or not affected (HSCR-only) by enterocolitis and replication of results on a larger panel of patients allowed the identification of the HAEC susceptibility variant p.H187Q in the Oncostatin-M receptor (OSMR) gene (14.6% in HAEC and 5.1% in HSCR-only,p= 0.0024). Proteomic analysis on the lymphoblastoid cell lines from one HAEC patient homozygote for this variant and one HAEC wild-type patient revealed two well distinct clusters of proteins significantly up or downregulated upon OSM stimulation. I have then carried out a transcriptome analysis on Intraepithelial lymphocytes (IEL) derived from gut biopsies and on Peripheral Blood Monocyte Cells (PBMCs) from HAEC, HSCR-only and pediatric patients affected by neither Hirschsprung, nor inflammatory related diseases. The analysis on the IELs showed a clear clustering between the groups of patients and an enrichment in immune and inflammatory pathways in the HAEC group. The results showed an interesting role for the gene Onco- statin M (OSMR) as a potential modifier from HSCR to HAEC. Additionally, a potential genetic connection between Inflammatory Bowel Disease and HSCR using the UKBioBank was explored. The finding of a shared genetic background with other inflammatory disorders affecting the gut, and the evaluation of gene networks and pathways involved in inflammation provides further knowledge on the mechanisms of gut inflammation.