RICERCA ITALIANA     

Crohn's disease: gene-molecular analysis of the susceptibility genetic variants and genotype/phenotype correlations, particularly regarding the development of strictures and the fibrogenetic mechanisms of the disease.

Università degli Studi di Milano

Abstract

Crohn's Disease (CD) is an inflammatory bowel disease (IBD) of unknown aetiology, showing prevalent fibrostricturing, inflammatory or fistulizing pattern. Multiple mechanisms, including genetic, immunologic and environmental factors appear to be involved in the pathogenesis of CD. NOD2/CARD15 mutations appear to confer susceptibility to develop CD, particularly ileal fibrostricturing CD. Pathogenetic mechanisms leading to stenosis in CD are unknown, including the possible role of other genes in determining the disease pattern. CARD15 gene is mainly expressed in phagocytic cell lines and encodes for a protein inducing NF-kB activation. A defect of NF-kB activation has been shown in CD patients with CARD15 mutation. However, an increased NF-kB activation and release of pro-inflammatory mediators has been shown in CD gut, suggesting a disregulation in the inflammatory pathway. Genetic variations within locus IBD5 (5q31) cytokine gene cluster confers susceptibility to CD with a strong evidence of association of IBD5 to CD and Ulcerative Colitis (UC). The knowledge of genetic factors contributing to specific inflammatory phenotype may add clues regarding the pathogenesis of tissue damage in IBD. Aim of our study is therefore to investigate the role of candidate genes in determining the characteristics of the inflammatory response in CD, particularly fibrostenosis, and in particular to assess: 1) the association between the known CARD15 mutation and CD pattern; 2) the >>>

Principal Investigator

Gabriele BIANCHI PORRO Università degli Studi di MILANO

Research Objectives

To evaluate the prevalence of NOD2/CARD15, MDR1 e MUC3 allelic variants in CD population and to compare it to that of ulcerative colitis and healthy control populations.
To determine the relationship between the inflammatory genes and CD by genotyping specific identified SNPs in the each inflammatory gene in a selected group of patients with a clear-cut definition of CD and matched controls CD-free.
To establish the presence of linkage between IBDs candidate loci and CD families in order to identify possible CD candidate genes, focusing the attention to the structuring form.

To correlate allelic variants of IBD genes or other candidate genes that predispose people to CD with phenotype features of the disease. In particular, the association between NOD2/CARD15, MDR1 and MUC3 allelic variants and specific histological features of the stenosis, such as intestinal fibrosis and muscolarization of the submucosa, in a series of operated CD patients will be established.

The study will evaluate the mechanisms of fibrogenesis that predispose to the abnormal thickening of the intestinal wall and to the formation of stenoses in Crohn's disease in order to ascertain whether genetic mutations or polymorphisms associated with this disease predispose to an abnormal regulation of intestinal fibrogenesis.

First Results

Confirmation of the high prevalence of NOD2/CARD15 allelic variants in CD population, in comparison to ulcerative colitis and healthy control populations.
Existance of IBDs candidate loci in CD families and identification of possible CD candidate genes in patients with structuring CD.
Determination of the relationship between the inflammatory genes and CD by genotyping specific identified SNPs in the each inflammatory gene in a selected group of patients with a clear-cut definition of CD and matched controls CD-free.Existance of genotype/phenoptype correlation between the well-known allelic variants of IBD genes (NOD2/CARD15, MDR1 e MUC3) and possible other SNPs in the each inflammatory gene and specific features of CD patients.
Existance o specific correlations between NOD2/CARD15 allelic variants and fibrostricturing CD
Identification histological features of stenosis in CD patients delle stenosi with NOD2/CARD15 allelic variants.Identifications of specyfic mechanisms of fibrogenesis that predispose to the abnormal thickening of the intestinal wall and to the formation of stenoses in Crohn's disease in in patients with genetic mutations or polymorphisms associated with this disease predispose to an abnormal regulation of intestinal fibrogenesis.

Timescale

24 months

National and international background

The pathogenesis of CD consists in the interaction of three elements: genetic susceptibility factors, environmental precipitants and immune response/inflammatory elements (Shanahan et al 2002). The most compelling data of the importance of genetic factors in the pathogenesis of CD and UC derive from studies of concordance rates in twin pairs. The results of the twin studies have been complemented by the results of studies in familial inflammatory bowel disease (Satsangi et al, 1996). During the last decade, a number of genome-wide searches for IBD susceptibility loci have been published. Consensus has been reached by an International Consortium on IBD genetics that the genome-wide scan approach provides evidence for susceptibility loci for IBD on chromosome 16q12 (IBD1) and on chromosome 12q13 (IBD2) (The IBD International Genetics Consortium., 2001). Further loci of IBD susceptibility have been found on chromosomes: 6p21 (IBD3), 14q, 19p, 5p, 1p, 3q, 4q and 7p (Satsangi et al., 1996; Cho et al., 1998; Taylor et al., 2001). These results suggest the implication of a consistent number of genes in the pathogenesis of IBDs and particularly of CD. In 2001, two independent groups identified that the candidate gene in IBD1 was NOD2/CARD15 (MIM *605956) (Hugot et al 2001; Ogura et al 2001). NOD2/CARD15 is a member of the NOD1/Apaf1 family of apoptosis regulators. NOD2/CARD15 is expressed in monocytes where it is thought to function as a cytosolic receptor for bacterial >>>