MAPPING DRUG RESISTANCE GENES IN PLASMODIUM FALCIPARUM

疟疾寄生虫恶性疟原虫已对目前使用的大多数主要抗疟药物产生耐药性，严重妨碍了我们控制这一疾病的能力。了解耐药性的遗传基础将有助于深入了解抗疟药物的作用方式，并为开发新化合物和重新设计现有药物提供基础。我们建议利用恶性疟原虫密集微卫星图谱和新出现的基因组序列数据，以及统计遗传学的最新进展来定位耐药基因。我们的方法将涉及田间收集的寄生虫的表型和基因型特征。我们将测量从泰缅边境一个地点获得的疟疾寄生虫对四种重要抗疟化合物甲氟喹、奎宁、青蒿素和氯喹的体外敏感性。然后，我们将利用分布在寄生虫基因组中间隔5-10 cM的200个微卫星标记对这些寄生虫进行基因分型。为了定位含有耐药数量性状位点的基因组区域，我们将采用两阶段策略。首先，我们将使用方差成分连锁方法，其中我们使用遗传标记数据来推断寄生虫之间的亲缘关系。然后，我们将通过检查标记位点和潜在耐药性基因之间的连锁不平衡，精细绘制包含耐药性数量性状位点的基因组区域。候选基因将利用疟疾基因组计划中出现的序列数据进行鉴定。

The malaria parasite, Plasmodium falciparum, has developed resistance to most of the major classes of antimalarial drugs currently in use, which severly hampers our ability to control this disease. Knowledge of the genetic basis of resistance would provide insights into mode of action of antimalarial drugs, as well as providing a basis for development of novel compounds and redesign of existing drugs. We propose to exploit the dense microsatellite map and the emerging genome sequence data frm P. falciparum together with recent advances in statistical genetics to locate genes underlying drug resistance. Our approach will involve both phenotypic and genotypic characterization of field collected parasites. We will measure in vitro susceptibility to 4 important antimalarial compounds-mefloquine, quinine, artemisinin and chloroquine in malaria parasites obtained from a site on the Thai-Burmese border. We will then genotype these parasites for 200 microsatellite markers distributed at 5-10 cM intervals across the parasite genome. To locate genomic regions containing quantitative trait loci for drug resistance we will use two-stage strategy. First we will use variance component linkage methods in which we use genetic marker data to infer kinship relationships between parasites. We will then fine-scale map regions of the genome containing quantitative trait loci for drug resistance, by inspecting linkage disequilibrium between marker loci and genes underlying resistance. Candidate genes will be identified using sequence data emerging from the malaria genome project.