Plasmodium falciparum gametocytogenesis

描述（由申请人提供）：疟疾仍然是一个主要的世界卫生问题，每年造成100万至200万人死亡。引起疟疾的疟原虫有一个多阶段的生命周期，这有助于它们逃避宿主免疫反应的能力。为了传播疟疾，寄生虫必须经过性分化，变成成熟的配子体细胞，当蚊子吸食到这种配子体的血液后，配子体就可以受精并开始孢子发育。在寄生虫的生命周期中，从无性复制到性分化的关键转换的分子基础尚不清楚。我们的假设是，这种转变是由转录因子的激活引发的，这些转录因子调节影响配子细胞发生所需的基因表达。一旦确定了调节因子，就可以设计抑制剂来阻止配子细胞的发生，从而防止疟疾的传播。为了鉴定相关基因，我们从菌株3D7中分离出恶性疟原虫配子体产生（G+）和不产生（G-）的寄生虫系。第一个特定目标将是使用全基因组微阵列分析来比较在无性向有性转变期间从G+和G-克隆中收集的mRNA。这种比较应该能识别出最早的差异表达基因。具体目标2将分析参与调节这些基因的配子细胞特异性表达的因素。将测试基因的5‘和3’侧翼区域驱动特定阶段报告基因表达的能力，并通过启动子定位和基序分析来确定所需的特定调控区域。特异性目标3将通过确定G+和G-寄生虫系之间的遗传差异来确定诱导配子细胞发生所需的基因，以及与特异性目标2中确定的调控区域相互作用的基因。配子体发生与遗传差异的关系将通过对野生型G+寄生虫G系的互补和靶向基因破坏进一步分析。这一信息应提供新的候选基因，可用于未来设计控制疟疾传播的新策略。

DESCRIPTION (provided by applicant): Malaria continues to be a major world health problem, killing1-2 million people annually. The Plasmodium parasites that cause malaria have a multistage life cycle, which contributes to their ability to evade host immune responses. For malaria transmission, the parasite must undergo sexual differentiation into mature gametocytes that, when taken up in a blood meal by a mosquito can fertilize and begin sporogonic development. The molecular basis for the critical switch from asexual replication to sexual differentiation in the parasite's life cycle is unknown. Our hypothesis is that this transition is initiated by the activation of transcription factors that regulate the expression of genes required to effect gametocytogenesis. Once the regulatory factors are identified, inhibitors could be designed to block gametocytogenesis, which would prevent malaria transmission. To identify the genes involved, Plasmodium falciparum gametocyte producing (G+) and non-producing (G-) parasite lines were derived from strain 3D7 parasites. The first Specific Aim will be to use whole genome microarray analysis to compare mRNA harvested from the G+ and G- clones during the asexual to sexual transition. This comparison should identify the earliest differentially expressed genes. Specific Aim 2 will be to analyze the factors involved in regulating the gametocyte-specific expression of these genes. The ability of the 5' and 3' flanking regions of the genes to drive stage-specific reporter gene expression will be tested and the specific regulatory regions required will be identified by promoter mapping supplemented with motif analysis. Specific Aim 3 will be to identify the genes required for the induction of gametocytogenesis by determining the genetic differences between the G+ and G- parasite lines, as well as the genes that interact with the regulatory regions identified in Specific Aim 2. The relationship between gametocytogenesis and the genetic differences found will be further analyzed by complementation of the G- line and targeted gene disruption of wild type G+ parasites. This information should provide new gene candidates that could be used in the future to design new strategies to control malaria transmission.