On the genetic involvement of apoptosis-related genes in Crohn's disease as revealed by an extended association screen using 245 markers: no evidence for new predisposing factors.

Crohn's disease (CD) presents as an inflammatory barrier disease with characteristic destructive processes in the intestinal wall. Although the pathomechanisms of CD are still not exactly understood, there is evidence that, in addition to e.g. bacterial colonisation, genetic predisposition contributes to the development of CD. In order to search for predisposing genetic factors we scrutinised 245 microsatellite markers in a population-based linkage mapping study. These microsatellites cover gene loci the encoded protein of which take part in the regulation of apoptosis and (innate) immune processes. Respective loci contribute to the activation/suppression of apoptosis, are involved in signal transduction and cell cycle regulators or they belong to the tumor necrosis factor superfamily, caspase related genes or the BCL2 family. Furthermore, several cytokines as well as chemokines were included. The approach is based on three steps: analyzing pooled DNAs of patients and controls, verification of significantly differing microsatellite markers by genotyping individual DNA samples and, finally, additional reinvestigation of the respective gene in the region covered by the associated microsatellite by analysing single-nucleotide polymorphisms (SNPs). Using this step-wise process we were unable to demonstrate evidence for genetic predisposition of the chosen apoptosis- and immunity-related genes with respect to susceptibility for CD.

The PTPN22 620W allele is a risk factor for Wegener's granulomatosis.

OBJECTIVE: Analyses of families with multiple autoimmune disorders have revealed a functional polymorphism, 620W, in the intracellular tyrosine phosphatase gene PTPN22 as a predisposing factor for type 1 diabetes, seropositive rheumatoid arthritis, systemic lupus erythematosus, and Hashimoto thyroiditis, and the presence of the PTPN22 protein appears to herald the development of autoantibodies in these disorders. This study therefore examined whether the functionally relevant PTPN22 polymorphism is associated with Wegener's granulomatosis (WG). METHODS: A population-based study was performed for the PTPN22 polymorphism in 199 patients with WG and in 399 healthy individuals. The R620W variation was investigated by simple restriction fragment-length polymorphism analysis. RESULTS: The PTPN22 620W allele frequency was significantly increased in antineutrophil cytoplasmic antibody (ANCA)-positive WG patients compared with healthy controls (P < 0.001). The association was particularly striking in patients with kidney, lung, eye, and peripheral nervous system involvement (i.e., those with generalized WG). CONCLUSION: The PTPN22 620W allele appears to be involved in the pathogenesis of WG, and ANCA positivity seems to be the hallmark.