Genetic control of malaria parasite proliferation

恶性疟原虫在红细胞（RBC）中的增殖形成了最具破坏性的人类疟疾形式的特征性间日热周期的基础。在生命周期的红细胞期的高无性繁殖率与严重的疾病有关。血液阶段的恶性疟原虫可以在培养的红细胞中维持，因此体外培养是寄生虫生物学研究、侵袭阻断疫苗开发和药物作用的基石。虽然红细胞中寄生虫生长的基本步骤已被很好地表征，但控制这些过程的基因和分子事件却知之甚少。使用现代基因组学工具的经典遗传方法提供了一种找到这些决定因素的独特方法。本研究的目的是利用高分辨率的微卫星连锁图沿着与体外生长相关性状的测量，以找到控制这些表型的基因座。鉴定的基因座可用于以生物学相关的方式靶向新出现的恶性疟原虫序列数据，以鉴定RBC中寄生虫增殖的机制。该提案的假设是，复杂的“生长速率”由可以测量和映射的更简单的离散步骤组成，从而有效地使用基因组数据库来确定生长相关基因。该假设的初步研究是使用放射性标记的次黄嘌呤掺入来量化寄生虫生长，以量化HB3xDd2杂交后代增殖率的遗传差异。该性状的数量性状基因座（QTL）定位已经确定了9号和13号染色体上基因的显着影响。具体目标1是精确测量生长速率的基础性状，包括每一次生殖产生的裂殖子侵入RBC的效率和选择性以及培养同步性。在具体目标2中，这些性状的遗传控制变异将通过QTL定位在基因组中进行表征和定位，以建立嵌套效应和重要基因位置的概况。具体目标3将使用微卫星标记将突出的QTL峰界定为定位QTL峰，以定位挖掘现有的恶性疟原虫基因组序列和候选基因的基因转录数据。这些研究代表了一种将重要的生物过程叠加在全基因组数据上的新方法，其目标是阐明疟疾干预的新途径。

Proliferation of Plasmodium falciparum in red blood cells (RBC) forms the basis for the tertian fever cycles characteristic of the most devastating form of human malaria. High asexual multiplication rate during the erythrocytic phase of the life cycle is associated with severe disease. Blood stage P. falciparum parasites can be maintained in cultured RBC, and thus in vitro cultivation is the cornerstone of research into parasite biology, invasion-blocking vaccine development, and drug effects. Although the basic steps of parasite growth in RBC are well characterized, the genes and molecular events controlling these processes are poorly understood. A classical genetic approach using modern genomics tools offers a unique way to find these determinants. The goal of this research is to exploit a high-resolution microsatellite linkage map along with measurements of in vitro growth-related traits to find loci controlling these phenotypes. Identified loci can be used to target the emerging P. falciparum sequence data in a biologically relevant way to identify mechanisms of parasite multiplication in RBC. The hypothesis of this proposal is that complex 'growth rate' is comprised of simpler discrete steps that can be measured and mapped, leading to efficient use of genome databases to pinpoint growth-related genes. The initial investigation of this hypothesis was to quantify heritable differences in the proliferation rate of progeny rates of the HB3xDd2 cross using the incorporation of radiolabeled hypoxanthine to quantify parasite growth. Quantitative trait loci (QTL) mapping of the trait has identified significant effects from genes on chromosomes 9 and 13. Specific Aim 1 is to precisely measure traits that underlie the growth rate, including efficiency and selectivity of RBC invasion by merozoites produced per schizogony and culture synchronicity. In Specific Aim 2, the genetically controlled variation in these traits will be characterized and localized in the genome by QTL mapping to build a profile of nested effects and positions of important genes. Specific Aim 3 will use microsatellite markers delimiting prominent QTL peaks to positionally QTL peaks to positionally mine existing P. falciparum genome sequence and gene transcription data for candidate genes. These studies represent a novel approach to overlay important biological processes on whole genome data, with the goal of elucidating new avenues for malaria intervention.