Polymorphisms In The NOTCH4 Gene In Inflammatory Bowel Disease

Background Inflammatory bowel disease (IBD) is a chronic and non-specific inflammatory disease which comprises Crohn's disease(CD),ulcerative colitis(UC) and indeterminate type of colitis. The pathogenesis of IBD is not clear. It is commonly presumed to be a multifactorial disease caused by the effect of enterobacteria and environmental factors on the hereditary susceptibility cohorts, and presented with excessive immunoreaction in intestinal mucosa. Epidemiological evidence shows a strong hereditary susceptibility contribution to IBD including high incidence of IBD in certain ethnic groups, family-cluster phenomenon and the concordance in identical twins. This was validated by the results of holo-genome scanning and predisposing genes.Recently, some important progresses have been made on the predisposing genes of IBD in 1996. For instance, NOD2/CARD15 gene was identified as the first susceptibility locus for CD adjacent to the centromere on chromosome 16. The NOD2/CARD15 gene product is expressed in monocytes, and can activate nuclear transcription factor kappa-B (NF-κB) in inflammatory response together with bacteria lipopolysaccharides and peptidoglycans. Stoll and colleagues confirmed two haplotypes of DLG5 gene as predisposing genes for CD on chromosome 10q23 which were associated with IBD. Simultaneously, a Canadian group reported that functional mutations in OCTN genes on chromosome 5q31 were associated with CD. It is suggested that IBD is a complicated and multigenic disease with hereditary susceptibility. The predisposing genes and the virulence genes could be discovered and identified with the cognition for genetic mechanism of IBD, which plays important roles in the genetic treatment, genetic counseling and reasonable preservation of susceptible population.Previous investigations showed that the polymorphisms of NOD2/CARD15 gene, DLG5 gene and OCTN gene were associated with IBD of European. Reports from Japan and Hong Kong demonstrated a negative correlation between the polymorphism of NOD2/CARD15 gene and IBD in Asians. Studies from our country with small sample size confirmed the absence of polymorphism of NOD2/CARD15 gene in Chinese. But there was no report about the relationship between DLG5 gene, OCTN gene and IBD in Chinese. Therefore, many studies focused on finding the predisposing genes of IBD. Some sites of human leukocyte antigen (HLA) class on chromosome 6p21.3 were associated with IBD. NOTCH4 gene is located on theⅢdomain of HLA class and has abundant polymorphisms, indicating its role of a candidate predisposing gene in IBD.Objective To detect the genetic polymorphism of NOTCH4 gene, DLG5 gene, OCTN gene and NOD2 /CARD15 gene and its relationship with IBD (CD and UC) in a large polulation of independent Chinese Han. Methods The study population comprised 63 patients with CD, 138 patients with UC, and 186 healthy controls from Chinese Han people. The genetic polymorphisms of those genes (NOTCH4 rs915894, rs422951, rs1044506; DLG5 rs1248696 G/A,rs2289310 C/A;OCTN rs1050152 C/T,rs2631367 G/C;NOD2 /CARD15 rs2066844 C/T,rs2066845 G/C) were analyzed by PCR–SSP, PCR-RFLP and DNA sequencing for single nucleotide polymorphisms (SNPs). And immunohistochemical method was used to detect the expression of Notch4 in colonic mucosa from 50 patients with UC and 32 nonneoplastic tissues adjacent colorectal carcinoma as normal controls. Data were analyzed byχ2 test and haplotype analysis by SAS statistic software.Results①Although the NOTCH4 gene (rs915894C/A, rs422951A/G and rs1044506C/A)polymorphisms were not significantly associated with the risk of IBD separately, haplotype analysis revealed that the individuals carrying more variant haplotype genotypes had more higher risk of CD. Consistently, the NOTCH4 haplotype genotypes with 1–4 variant (risk) alleles (rs915894 and rs422951) were associated with an increased risk of CD compared to the genotypes no variant within.②There was no DLG5 gen(ers1248696 G/A),OCTN gene (rs1050152 C/T,rs2631367 G/C)and NOD2 /CARD15 gene(rs2066844 C/T,rs2066845 G/C) polymorphisms in Chinese Han people. There was DLG5 gene (rs2289310 C/A) polymorphisms in Han people, but it was not associated with IBD.③Immunohistochemical results showed that the positive rates of Notch4 were 64.0% in the ulcerative colitis tissues and 59.4% in the normal controls, respectively. Statistical analysis suggested that the positive rates of Notch4 were not significantly different between the ulcerative colitis and normal controls (P >0.05). Conclusion①NOTCH4 gene(rs915894C/A, rs422951A/G)polymorphisms appear to contribute to risk of CD in the Chinese Han people. Simultaneous mutation of the two sites may be occurred in patients with CD.②The polymorphisms of NOTCH4 gene(rs915894C/A, rs422951A/G and rs1044506C/A) were not associated with UC, which is identical to the immunohistochemical results.③DLG5 gene(rs1248696 G/A)and OCTN gene(rs1050152 C/T, rs2631367 G/C) did not show genetic polymorphisms in Chinese Han people. And DLG5 gene (rs2289310 C/A) polymorphisms were not associated with IBD.④NOD2 /CARD15 gene (rs2066844 C/T,rs2066845 G/C) did not show genetic polymorphisms in Chinese Han people, which was similar to the studies on other Orientals.