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三热周期的基础。在生命周期的红细胞阶段，高无性繁殖率与严重的疾病有关。血期恶性疟原虫可以在体外培养的红细胞中维持，因此体外培养是寄生虫生物学、入侵阻断疫苗开发和药物作用研究的基石。虽然寄生虫在红细胞中生长的基本步骤被很好地描述，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为找到这些决定因素提供了一种独特的方法。本研究的目标是利用高分辨率微卫星连锁图谱以及体外生长相关性状的测量来找到控制这些表型的位点。已鉴定的位点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，以确定寄生虫在红细胞中的增殖机制。该提案的假设是，复杂的“生长速度”由可以测量和绘制的更简单的离散步骤组成，从而有效地利用基因组数据库来精确定位与生长相关的基因。对这一假说的初步研究是通过结合放射性标记的次黄嘌呤来量化寄生虫生长，从而量化HB3xDd2杂交后代增殖率的遗传差异。该性状的数量性状位点（QTL）定位鉴定了9号和13号染色体上的基因对该性状的显著影响。具体目标1是精确测量生长速率的基础性状，包括分裂分裂产生的分裂子入侵RBC的效率和选择性和培养同步性。在Specific Aim 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，以建立巢状效应和重要基因位置的概况。Specific Aim 3将利用微卫星标记将突出的QTL峰划分为定位QTL峰，对现有恶性疟原虫基因组序列和候选基因的基因转录数据进行定位挖掘。这些研究代表了一种覆盖全基因组数据的重要生物学过程的新方法，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.