Department of Radiation Biology, Beckman Research Institute of City of Hope, Duarte, California, United States of America.
PLoS One. 2012;7(9):e44262. doi: 10.1371/journal.pone.0044262. Epub 2012 Sep 6.
Mice that are deficient for glutathione peroxidases 1 and 2 (GPX) show large variations in the penetrance and severity of colitis in C57BL/6J and 129S1/SvImJ backgrounds. We mapped a locus contributing to this difference to distal chromosome 2 (∼119-133 mbp) and named it glutathione peroxidase-deficiency-associated colitis 1 (Gdac1). The aim of this study was to identify the best gene candidates within the Gdac1 locus contributing to the murine colitis phenotype.
METHOD/PRINCIPAL FINDINGS: We refined the boundaries of Gdac1 to 118-125 mbp (95% confidence interval) by increasing sample size and marker density across the interval. The narrowed region contains 128 well-annotated protein coding genes but it excludes Fermt1, a human inflammatory bowel disease candidate that was within the original boundaries of Gdac1. The locus we identified may be the Cdcs3 locus mapped by others studying IL10-knockout mice. Using in silico analysis of the 128 genes, based on published colon expression data, the relevance of pathways to colitis, gene mutations, presence of non-synonymous-single-nucleotide polymorphisms (nsSNPs) and whether the nsSNPs are predicted to have an impact on protein function or expression, we excluded 42 genes. Based on a similar analysis, twenty-five genes from the remaining 86 genes were analyzed for expression-quantitative-trait loci, and another 15 genes were excluded.
CONCLUSION/SIGNIFICANCE: Among the remaining 10 genes, we identified Pla2g4f and Duox2 as the most likely colitis gene candidates, because GPX metabolizes PLA2G4F and DUOX2 products. Pla2g4f is a phospholipase A2 that has three potentially significant nsSNP variants and showed expression differences across mouse strains. PLA2G4F produces arachidonic acid, which is a substrate for lipoxygenases and, in turn, for GPXs. DUOX2 produces H(2)O(2) and may control microbial populations. DUOX-1 and -2 control microbial populations in mammalian lung and in the gut of several insects and zebrafish. Dysbiosis is a phenotype that differentiates 129S1/SvImJ from C57BL/6J and may be due to strain differences in DUOX2 activity.
谷胱甘肽过氧化物酶 1 和 2（GPX）缺乏的小鼠在 C57BL/6J 和 129S1/SvImJ 背景下表现出结肠炎的穿透率和严重程度的巨大差异。我们将导致这种差异的一个基因座映射到远端染色体 2（约 119-133mbp）上，并将其命名为谷胱甘肽过氧化物酶缺乏相关结肠炎 1（Gdac1）。本研究的目的是鉴定 Gdac1 基因座内对小鼠结肠炎表型有贡献的最佳候选基因。
方法/主要发现：我们通过增加间隔内的样本量和标记密度，将 Gdac1 的边界缩小到 118-125mbp（95%置信区间）。缩小的区域包含 128 个注释良好的蛋白质编码基因，但不包括 Fermt1，Fermt1 是人类炎症性肠病候选基因，位于 Gdac1 的原始边界内。我们确定的基因座可能是其他研究 IL10 敲除小鼠的人研究的 Cdcs3 基因座。基于对 128 个基因的计算机分析，根据已发表的结肠表达数据，对结肠炎相关途径、基因突变、非同义单核苷酸多态性（nsSNP）的存在以及 nsSNP 是否预测对蛋白质功能或表达有影响进行分析，我们排除了 42 个基因。基于类似的分析，对其余 86 个基因中的 25 个基因进行了定量表达数量性状基因座分析，并排除了另外 15 个基因。
结论/意义：在剩下的 10 个基因中，我们确定 Pla2g4f 和 Duox2 是最有可能的结肠炎候选基因，因为 GPX 代谢 PLA2G4F 和 DUOX2 产物。Pla2g4f 是一种磷脂酶 A2，有三个潜在的重要 nsSNP 变体，在不同的小鼠品系中表现出表达差异。PLA2G4F 产生花生四烯酸，花生四烯酸是脂氧合酶的底物，反过来又是 GPXs 的底物。DUOX2 产生 H2O2，可能控制微生物种群。DUOX-1 和 -2 控制哺乳动物肺部和几种昆虫和斑马鱼肠道中的微生物种群。肠道微生物紊乱是区分 129S1/SvImJ 和 C57BL/6J 的表型，可能是由于 DUOX2 活性的菌株差异所致。
