Program in Molecular Structure and Function, Hospital for Sick Children, and Department of Biochemistry & Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
mBio. 2012 Nov 13;3(6):e00321-12. doi: 10.1128/mBio.00321-12.
The Toxoplasma gondii SRS gene superfamily is structurally related to SRS29B (formerly SAG1), a surface adhesin that binds host cells and stimulates host immunity. Comparative genomic analyses of three Toxoplasma strains identified 182 SRS genes distributed across 14 chromosomes at 57 genomic loci. Eight distinct SRS subfamilies were resolved. A core 69 functional gene orthologs were identified, and strain-specific expansions and pseudogenization were common. Gene expression profiling demonstrated differential expression of SRS genes in a developmental-stage- and strain-specific fashion and identified nine SRS genes as priority targets for gene deletion among the tissue-encysting coccidia. A Δsag1 sag2A mutant was significantly attenuated in murine acute virulence and showed upregulated SRS29C (formerly SRS2) expression. Transgenic overexpression of SRS29C in the virulent RH parent was similarly attenuated. Together, these findings reveal SRS29C to be an important regulator of acute virulence in mice and demonstrate the power of integrated genomic analysis to guide experimental investigations.
Parasitic species employ large gene families to subvert host immunity to enable pathogen colonization and cause disease. Toxoplasma gondii contains a large surface coat gene superfamily that encodes adhesins and virulence factors that facilitate infection in susceptible hosts. We generated an integrated bioinformatic resource to predict which genes from within this 182-gene superfamily of adhesin-encoding genes play an essential role in the host-pathogen interaction. Targeted gene deletion experiments with predicted candidate surface antigens identified SRS29C as an important negative regulator of acute virulence in murine models of Toxoplasma infection. Our integrated computational and experimental approach provides a comprehensive framework, or road map, for the assembly and discovery of additional key pathogenesis genes contained within other large surface coat gene superfamilies from a broad array of eukaryotic pathogens.
弓形虫 SRS 基因超家族在结构上与 SRS29B（以前称为 SAG1）相关，SRS29B 是一种表面黏附素，可与宿主细胞结合并刺激宿主免疫。对三种弓形虫株的比较基因组分析鉴定出 182 个 SRS 基因，分布在 14 条染色体上的 57 个基因组位点。确定了 8 个不同的 SRS 亚家族。鉴定出了核心的 69 个功能基因直系同源物，并且常见的是株系特异性的扩展和假基因化。基因表达谱分析表明 SRS 基因在发育阶段和株系特异性方面存在差异表达，并确定了 9 个 SRS 基因作为组织包囊球虫中基因缺失的优先靶标。Δsag1sag2A 突变体在小鼠急性毒力中显著减弱，并表现出 SRS29C（以前称为 SRS2）表达上调。在毒力 RH 亲本中过表达 SRS29C 的转基因同样减弱。这些发现共同表明 SRS29C 是小鼠急性毒力的重要调节剂，并证明了综合基因组分析指导实验研究的力量。
寄生虫种系利用大型基因家族来颠覆宿主免疫，以实现病原体定植并引起疾病。弓形虫含有一个大型表面外壳基因超家族，该基因超家族编码黏附素和毒力因子，有助于易感宿主的感染。我们生成了一个综合的生物信息资源，以预测该黏附素编码基因超家族中的哪些基因在宿主-病原体相互作用中发挥重要作用。针对预测的候选表面抗原的靶向基因缺失实验确定 SRS29C 是小鼠弓形虫感染模型中急性毒力的重要负调节剂。我们的综合计算和实验方法为组装和发现来自广泛真核病原体的其他大型表面外壳基因超家族中的其他关键发病机制基因提供了一个全面的框架或路线图。
