Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA.
PLoS Pathog. 2010 Sep 2;6(9):e1001088. doi: 10.1371/journal.ppat.1001088.
Although it has recently been shown that A/J mice are highly susceptible to Staphylococcus aureus sepsis as compared to C57BL/6J, the specific genes responsible for this differential phenotype are unknown. Using chromosome substitution strains (CSS), we found that loci on chromosomes 8, 11, and 18 influence susceptibility to S. aureus sepsis in A/J mice. We then used two candidate gene selection strategies to identify genes on these three chromosomes associated with S. aureus susceptibility, and targeted genes identified by both gene selection strategies. First, we used whole genome transcription profiling to identify 191 (56 on chr. 8, 100 on chr. 11, and 35 on chr. 18) genes on our three chromosomes of interest that are differentially expressed between S. aureus-infected A/J and C57BL/6J. Second, we identified two significant quantitative trait loci (QTL) for survival post-infection on chr. 18 using N(2) backcross mice (F(1) [C18A]xC57BL/6J). Ten genes on chr. 18 (March3, Cep120, Chmp1b, Dcp2, Dtwd2, Isoc1, Lman1, Spire1, Tnfaip8, and Seh1l) mapped to the two significant QTL regions and were also identified by the expression array selection strategy. Using real-time PCR, 6 of these 10 genes (Chmp1b, Dtwd2, Isoc1, Lman1, Tnfaip8, and Seh1l) showed significantly different expression levels between S. aureus-infected A/J and C57BL/6J. For two (Tnfaip8 and Seh1l) of these 6 genes, siRNA-mediated knockdown of gene expression in S. aureus-challenged RAW264.7 macrophages induced significant changes in the cytokine response (IL-1 beta and GM-CSF) compared to negative controls. These cytokine response changes were consistent with those seen in S. aureus-challenged peritoneal macrophages from CSS 18 mice (which contain A/J chromosome 18 but are otherwise C57BL/6J), but not C57BL/6J mice. These findings suggest that two genes, Tnfaip8 and Seh1l, may contribute to susceptibility to S. aureus in A/J mice, and represent promising candidates for human genetic susceptibility studies.
尽管最近的研究表明 A/J 小鼠对金黄色葡萄球菌败血症的易感性高于 C57BL/6J，但导致这种表型差异的具体基因尚不清楚。我们使用染色体替换品系 (CSS) 发现，染色体 8、11 和 18 上的基因座影响 A/J 小鼠对金黄色葡萄球菌败血症的易感性。然后，我们使用两种候选基因选择策略来确定与金黄色葡萄球菌易感性相关的这三个染色体上的基因，并靶向两种基因选择策略都确定的基因。首先，我们使用全基因组转录谱分析鉴定了我们感兴趣的三个染色体上的 191 个（8 号染色体上的 56 个、11 号染色体上的 100 个和 18 号染色体上的 35 个）差异表达的基因，这些基因在金黄色葡萄球菌感染的 A/J 和 C57BL/6J 之间存在差异表达。其次，我们使用 N(2)回交小鼠（F(1)[C18A]xC57BL/6J）鉴定了染色体 18 上两个与存活相关的显著数量性状基因座 (QTL)。染色体 18 上的 10 个基因（March3、Cep120、Chmp1b、Dcp2、Dtwd2、Isoc1、Lman1、Spire1、Tnfaip8 和 Seh1l）映射到两个显著的 QTL 区域，并且也被表达谱选择策略鉴定出来。通过实时 PCR，这 10 个基因中的 6 个（Chmp1b、Dtwd2、Isoc1、Lman1、Tnfaip8 和 Seh1l）在金黄色葡萄球菌感染的 A/J 和 C57BL/6J 之间表现出明显不同的表达水平。对于这 6 个基因中的 2 个（Tnfaip8 和 Seh1l），金黄色葡萄球菌挑战 RAW264.7 巨噬细胞中的基因表达的 siRNA 介导的敲低导致细胞因子反应（IL-1β和 GM-CSF）发生显著变化，与阴性对照相比。这些细胞因子反应变化与 CSS 18 小鼠（含有 A/J 染色体 18，但其他方面为 C57BL/6J）中金黄色葡萄球菌挑战的腹腔巨噬细胞中观察到的变化一致，但与 C57BL/6J 小鼠不一致。这些发现表明，两个基因 Tnfaip8 和 Seh1l 可能导致 A/J 小鼠对金黄色葡萄球菌的易感性，并代表人类遗传易感性研究的有前途的候选基因。
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