Institute for Immunology and Infection Research, University of Edinburgh, UK.
BMC Genomics. 2012 Mar 21;13:106. doi: 10.1186/1471-2164-13-106.
Drug resistance in the malaria parasite Plasmodium falciparum severely compromises the treatment and control of malaria. A knowledge of the critical mutations conferring resistance to particular drugs is important in understanding modes of drug action and mechanisms of resistances. They are required to design better therapies and limit drug resistance.A mutation in the gene (pfcrt) encoding a membrane transporter has been identified as a principal determinant of chloroquine resistance in P. falciparum, but we lack a full account of higher level chloroquine resistance. Furthermore, the determinants of resistance in the other major human malaria parasite, P. vivax, are not known. To address these questions, we investigated the genetic basis of chloroquine resistance in an isogenic lineage of rodent malaria parasite P. chabaudi in which high level resistance to chloroquine has been progressively selected under laboratory conditions.
Loci containing the critical genes were mapped by Linkage Group Selection, using a genetic cross between the high-level chloroquine-resistant mutant and a genetically distinct sensitive strain. A novel high-resolution quantitative whole-genome re-sequencing approach was used to reveal three regions of selection on chr11, chr03 and chr02 that appear progressively at increasing drug doses on three chromosomes. Whole-genome sequencing of the chloroquine-resistant parent identified just four point mutations in different genes on these chromosomes. Three mutations are located at the foci of the selection valleys and are therefore predicted to confer different levels of chloroquine resistance. The critical mutation conferring the first level of chloroquine resistance is found in aat1, a putative aminoacid transporter.
Quantitative trait loci conferring selectable phenotypes, such as drug resistance, can be mapped directly using progressive genome-wide linkage group selection. Quantitative genome-wide short-read genome resequencing can be used to reveal these signatures of drug selection at high resolution. The identities of three genes (and mutations within them) conferring different levels of chloroquine resistance generate insights regarding the genetic architecture and mechanisms of resistance to chloroquine and other drugs. Importantly, their orthologues may now be evaluated for critical or accessory roles in chloroquine resistance in human malarias P. vivax and P. falciparum.
疟原虫恶性疟对药物的耐药性严重影响疟疾的治疗和控制。了解导致特定药物耐药的关键突变对于理解药物作用模式和耐药机制非常重要。这些突变对于设计更好的治疗方法和限制耐药性至关重要。
一种编码膜转运蛋白的基因 (pfcrt) 的突变已被确定为恶性疟原虫对氯喹耐药的主要决定因素，但我们缺乏对高水平氯喹耐药的全面了解。此外，其他主要人类疟疾寄生虫间日疟原虫的耐药决定因素尚不清楚。为了解决这些问题，我们研究了在实验室条件下逐步选择的具有高水平氯喹耐药性的啮齿动物疟原虫 P. chabaudi 的同系物中氯喹耐药的遗传基础。
通过使用高氯喹耐药突变体和遗传上不同的敏感株之间的遗传交叉进行连锁群选择，定位了包含关键基因的基因座。使用新型高分辨率定量全基因组重测序方法揭示了三个选择区域，这些区域位于 chr11、chr03 和 chr02 上，随着药物剂量的增加，这三个区域在三个染色体上逐渐出现。氯喹耐药亲本的全基因组测序仅在这些染色体上的不同基因中发现了四个点突变。三个突变位于选择谷的焦点，因此预计会赋予不同水平的氯喹耐药性。第一个水平的氯喹耐药性的关键突变发生在 aat1 中，这是一个假定的氨基酸转运体。
可通过渐进式全基因组连锁群选择直接绘制赋予可选择表型（如耐药性）的数量性状基因座。定量全基因组短读长基因组重测序可用于以高分辨率揭示这些药物选择的特征。三个基因（及其内部突变）赋予不同水平氯喹耐药性的鉴定提供了有关氯喹和其他药物耐药性的遗传结构和机制的深入了解。重要的是，它们的同源物现在可以评估在人类疟疾间日疟原虫和恶性疟原虫中氯喹耐药的关键或辅助作用。
