Analysis of the inflammatory bowel disease susceptome and resistome using a forward genetics approach

炎症性肠病（IBD），包括溃疡性结肠炎和克罗恩病，在严重程度上变化很大，有很强的遗传成分，但不表现为简单的孟德尔特征。这表明，个体之间的环境差异，包括肠道微生物组的差异，或者，许多基因座遗传差异的累积效应，可能决定疾病表型是否存在。在小鼠中，已知有几种突变有利于IBD或抑制肠道炎症。但是，基于迄今为止从遗传分析中获得的有限信息，还不能对IBD的发病机制进行全面的描述，人类IBD也不能严格地归因于已知对小鼠有影响的突变。在这里，我们建议对IBD采取无偏见、无假设的观点，使用种系诱变来分析小鼠的这种现象。在具体目标1中，我们打算使用IBD小鼠模型（右旋糖酐硫酸钠（DSS）结肠炎模型）筛选在特定遗传背景下导致IBD易感性或耐药的突变，对这些突变进行定位克隆，并形成关于每个验证基因参与疾病发病机制的假设。我们创建的突变将识别可能导致人类IBD疾病的候选基因座，指出潜在的治疗靶点，并产生关于其他基因参与IBD耐药或易感性的可测试假设。此外，在特定的目的2中，我们将研究一种突变小鼠，其编码1位点蛋白酶（S1P）的Mbtps1存在错义错误，该突变小鼠被发现易患IBD。这一提议旨在对IBD的发病机制进行新的发现，最终可能导致新的靶点或治疗方法。

Inflammatory bowel diseases (IBD), including both ulcerative colitis and Crohn’s disease, are extremely variable in severity, and have strong genetic components, but do not behave as simple Mendelian traits. This suggests that environmental differences between individuals including differences in the intestinal microbiome or alternatively, the cumulative effects of genetic differences at numerous loci may determine whether the disease phenotype is present. In mice, several mutations are known to favor IBD or to inhibit intestinal inflammation. But a comprehensive picture of the pathogenesis of IBD cannot be assembled based on the limited information so far available from genetic analyses, nor can human IBD be stringently ascribed to mutations that are known to be influential in mice. Here we propose to take an unbiased, hypothesis-free view of IBD, using germline mutagenesis to analyze the phenomenon in mice. In specific aim 1, we intend to screen for mutations that cause either susceptibility or resistance to IBD on a defined genetic background using the a mouse model of IBD (the Dextran sodium sulfate (DSS) colitis model), positionally clone these mutations, and form hypotheses concerning the participation of each validated gene in the disease pathogenesis. The mutations that we create will identify candidate loci that may cause IBD disease in humans, point to potential targets for therapy and yield testable hypotheses concerning the involvement of other genes in IBD resistance or susceptibility. Furthermore, in specific aim 2, we will investigate one mutant mouse with a missense error in Mbtps1, encoding the site-1 protease (S1P), which was found to be susceptible for IBD. This proposal aims toward new discoveries about the pathogenesis of IBD, which may eventually lead to new targets or therapies.