Discovery of parasite virulence genes reveals a unique regulator of chromosome condensation 1 ortholog critical for efficient nuclear trafficking
Discovery of parasite virulence genes reveals a unique regulator of chromosome condensation 1 ortholog critical for efficient nuclear trafficking
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DOI：
10.1073/pnas.0701893104
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发表时间：
2007-06-12
影响因子：
11.1
通讯作者：
Knoll, Laura J.
中科院分区：
文献类型：
--
作者：
Frankel, Matthew B.;Mordue, Dana G.;Knoll, Laura J.
真核寄生虫是世界范围内发病和死亡的主要原因，但对其毒力的遗传基础知之甚少。在这里，我们提出了一个向前的遗传筛选研究的发病机制，在原生动物寄生虫弓形虫。采用改良的标记突变技术，对6,300株T.在细胞培养和小鼠感染中比较弓形虫插入突变体，以鉴定体内特异性需要的基因。39个无毒突变体之一被破坏的染色体凝聚1（RCC 1），这是至关重要的模型系统中的核贩运的调节器的分歧直系同源物。虽然这种RCC 1突变体在标准组织培养条件下生长类似于野生型，但在营养限制下生长受损。突变体寄生虫与T.弓形虫RCC 1基因完全恢复小鼠的毒力和低营养条件下的生长。进一步的分析表明，在RCC 1突变体的核运输中存在显著缺陷。这些结果表明，核运输速率伊萨影响体内和体外低营养条件下生长的关键因素。此外，我们观察到，虽然RCC 1蛋白在从人类到酵母的生物体中高度保守，但没有原生动物寄生虫编码特征RCC 1。这种蛋白质差异可能代表了核质转运的独特机制。这项研究说明了这种正向遗传学方法的力量，以确定非典型的毒力机制。
Eukaryotic parasites are a leading cause of morbidity and mortality worldwide, yet little is known about the genetic basis of their virulence. Here, we present a forward genetic screen to study pathogenesis in the protozoan parasite Toxoplasma gondii. By using modified signature-tagged mutagenesis, the growth of 6,300 T. gondii insertional mutants was compared in cell culture and murine infection to identify genes required specifically in vivo. One of the 39 avirulent mutants is disrupted in a divergent ortholog of the regulator of chromosome condensation 1 (RCC1), which is critical for nuclear trafficking in model systems. Although this RCC1 mutant grows similar to wild type in standard tissue culture conditions, it is growth-impaired under nutrient limitation. Genetic complementation of mutant parasites with the T. gondii RCC1 gene fully restores both virulence in mice and growth under low-nutrient conditions. Further analysis shows that there is a significant defect in nuclear trafficking in the RCC1 mutant. These findings suggest that the rate of nuclear transport isa critical factor affecting growth in low-nutrient conditions in vivo and in vitro. Additionally, we observed that although RCC1 proteins are highly conserved in organisms from humans to yeast, no protozoan parasite encodes a characteristic RCC1. This protein divergence may represent a unique mechanism of nucleocytoplasmic transport. This study illustrates the power of this forward genetics approach to identify atypical virulence mechanisms.