Malaria Parasite Sexual Development, Drug Resistance, and Evolution

在过去的一年里，我们继续研究恶性疟原虫基因组多样性，耐药性，基因调控，并使用遗传作图，微阵列，基因敲除，遗传杂交，群体遗传学和其他方法的毒力。最终目标是将遗传多态性与寄生虫生物学和疾病联系起来，并开发控制疟疾的新方法。 我们从185个培养适应的分离株中获得了数千个单核苷酸多态性（SNP），测试了寄生虫对7种抗疟药物的反应，在全基因组关联分析中使用基因型/表型数据，并确定了与寄生虫对甲氟喹（MQ）、双氢青蒿素（DHA）和其他药物的药物反应相关的候选基因。 最近，我们启动了一个项目，系统地表征寄生虫的差异反应，数以千计的化学化合物，并收集了数百个差异化学表型（DCP）。通过基因图谱已经确定了其中一些差异的遗传变异。通过对候选基因的进一步研究，可以推断出基因的功能。这项研究还确定了许多潜在的抗疟化合物，其中一些正在进行体内测试。 为了研究毒力和疾病表型，我们正在开发约氏疟原虫的遗传图谱。疾病表型是寄生虫和宿主相互作用的结果。使用近交系小鼠将大大减少宿主因素对表型测定的影响。我们已经确定了600个微卫星（MS）标记，进行了三个遗传杂交使用不同的寄生虫分离株，并获得了45个后代的杂交。我们正在克隆更多的后代，并评估后代的各种表型。 几项研究表明，同基因寄生虫对之间的基因表达差异，但没有DNA序列的变化可以确定，包括我们以前描述的pfmdv 1。基因表达差异的一种可能性是基因表达的表观遗传调节。核小体定位是表观遗传基因调控机制之一。已经表明，相对于转录起始位点的核小体定相与RNA聚合酶II结合直接相关，并且起始位点下游的第一个核小体在活性和沉默基因中表现出差异定位。我们对寄生虫核小体位置、基因表达和寄生虫不同发育阶段的关系感兴趣，并获得了不同发育阶段的核小体位置。

In the past year, we continued to study P. falciparum genome diversity, drug resistance, gene regulation, and virulence using genetic mapping, microarray, gene knockout, genetic crosses, population genetics, and other approaches. The ultimate goals were to relate genetic polymorphisms to parasite biology and disease and to develop novel approaches to control malaria. We have obtained thousands of single nucleotide polymorphism (SNP) from 185 culture-adapted isolates, tested the parasites responses to 7 antimalarial drugs, used the genotype/phenotype data in genome-wide association analyses, and identified candidate genes associated with parasite drug responses to mefloquine (MQ), dihydroartemisinin (DHA) and other drugs. Recently, we initiated a project to systematically characterize parasite differential response to thousands of chemical compounds and have collected hundreds of differential chemical phenotypes (DCPs). Genetic variations underlying some of these differences have been identified through genetic mapping. Gene functions can be deduced after further studies of the candidate genes. This study also identified many potential antimalarial compounds, some of which are being tested in vivo. To study virulence and disease phenotype, we are developing a genetic map for Plasmodium yoelii. Disease phenotypes are the results of parasite and host interactions. Use of inbred mice will greatly reduce the influence of host factors on phenotype measurement. We have identified 600 microsatellite (MS) markers, performed three genetic crosses using different parasite isolates, and obtained 45 progeny from the crosses. We are in the process of cloning more progeny and evaluating various phenotypes from the progeny. Several studies showed differences in gene expression between pairs of isogenic parasites, but no changes in DNA sequences could be identified, including the pfmdv 1 we described previously. One possibility for the differences in gene expression is epigenetic regulation of gene expression. Nucleosome positioning is one of the epigenetic gene regulation mechanisms. It has been shown that nucleosome phasing relative to transcription start sites is directly correlated to RNA polymerase II binding, and the first nucleosome downstream of a start site exhibits differential positioning in active and silent genes. We are interested in the relationships in parasite nucleosome position, gene expression, and different parasite developmental stages and have obtained nucelosome positions from different developmental stages.