Garzón-Ospina Diego, Forero-Rodríguez Johanna, Patarroyo Manuel A
Molecular Biology and Immunology Department, Fundación Instituto de Inmunología de Colombia (FIDIC), Carrera 50 No, 26-20, Bogotá, DC, Colombia.
Malar J. 2014 Dec 13;13:495. doi: 10.1186/1475-2875-13-495.
The msp-7 gene has become differentially expanded in the Plasmodium genus; Plasmodium vivax has the highest copy number of this gene, several of which encode antigenic proteins in merozoites.
DNA sequences from thirty-six Colombian clinical isolates from P. vivax (pv) msp-7E, -7F and -7L genes were analysed for characterizing and studying the genetic diversity of these pvmsp-7 members which are expressed during the intra-erythrocyte stage; natural selection signals producing the variation pattern so observed were evaluated.
The pvmsp-7E gene was highly polymorphic compared to pvmsp-7F and pvmsp-7L which were seen to have limited genetic diversity; pvmsp-7E polymorphism was seen to have been maintained by different types of positive selection. Even though these copies seemed to be species-specific duplications, a search in the Plasmodium cynomolgi genome (P. vivax sister taxon) showed that both species shared the whole msp-7 repertoire. This led to exploring the long-term effect of natural selection by comparing the orthologous sequences which led to finding signatures for lineage-specific positive selection.
The results confirmed that the P. vivax msp-7 family has a heterogeneous genetic diversity pattern; some members are highly conserved whilst others are highly diverse. The results suggested that the 3'-end of these genes encode MSP-7 proteins' functional region whilst the central region of pvmsp-7E has evolved rapidly. The lineage-specific positive selection signals found suggested that mutations occurring in msp-7s genes during host switch may have succeeded in adapting the ancestral P. vivax parasite population to humans.
msp-7基因在疟原虫属中呈现出差异扩增；间日疟原虫该基因的拷贝数最高，其中一些编码裂殖子中的抗原蛋白。
分析来自36个哥伦比亚间日疟原虫临床分离株的msp-7E、-7F和-7L基因的DNA序列，以表征和研究这些在红细胞内期表达的间日疟原虫msp-7成员的遗传多样性；评估产生如此观察到的变异模式的自然选择信号。
与遗传多样性有限的间日疟原虫msp-7F和msp-7L相比，间日疟原虫msp-7E基因具有高度多态性；间日疟原虫msp-7E的多态性似乎是由不同类型的正选择维持的。尽管这些拷贝似乎是物种特异性重复，但在食蟹猴疟原虫基因组（间日疟原虫的姐妹分类群）中的搜索表明，这两个物种共享整个msp-7基因库。这导致通过比较直系同源序列来探索自然选择的长期影响，从而发现谱系特异性正选择的特征。
结果证实间日疟原虫msp-7家族具有异质的遗传多样性模式；一些成员高度保守，而另一些则高度多样。结果表明，这些基因的3'端编码MSP-7蛋白的功能区域，而间日疟原虫msp-7E的中央区域进化迅速。发现的谱系特异性正选择信号表明，宿主转换期间msp-7s基因发生的突变可能成功地使间日疟原虫祖先寄生虫群体适应了人类。
