STAGE SPECIFIC GENE EXPRESSION IN TOXOPLASMA GONDII

原生动物病原体弓形虫是导致疾病的重要原因。 在人类和家畜身上。弓形虫可引起急性和经常 免疫抑制患者的致死性机会性感染 心理治疗。以前有潜伏感染的艾滋病患者可能会发展为 弓形虫脑炎是发病和死亡的重要原因 死亡率。在中间宿主中，弓形虫以两种形式存在，即 速殖子和缓殖子。在感染的急性期， 侵袭性速殖子形式占主导地位，并对组织负责 毁灭。速殖子转变为封闭的缓殖子形式 在潜伏感染期间持续存在的组织囊肿，即使在健康的 目前正在接受抗弓形虫药物治疗的个人和患者。 因囊肿破裂而引起的先前潜伏感染的重新激活 在大脑或其他组织中导致速殖子重新出现 被认为是艾滋病活动性弓形虫病的主要原因 病人。由于组织囊肿参与了潜伏期的维持 感染和寄生虫的来源都在重新激活，这是重要的 研究速殖子和速殖子之间的相互转化机制 缓殖子阶段。为了研究阶段特异性基因的调控 在转化过程中，克隆了几个阶段特异的基因 包括两个与乳酸脱氢酶(LDH)同源性很高的基因 其他物种。一个LDH基因是缓殖子特异的，另一个是 速殖子特有的。研究阶段特异性的作用机制 为了调控这些LDH基因，将采取以下方法：(1) 乳酸脱氢酶多肽的表达谱将在 慢速殖子和速殖子相互转化的体外模型 分化，(2)LDH2基因的转录活性 阶段转化过程中的研究，(3)启动子和DNA序列结构域 负责发育转录的激活和调节 将通过缺失和突变分析来鉴定LDH2基因， 以及(4)缓殖子的功能意义--特别是 表达的LDH亚型将通过基因产生零突变来检测 替补。缓殖子LDH基因的基因置换研究 以确定其对包囊发育的重要性。 乳酸脱氢酶启动子中DNA调节域的鉴定 参与了他们的发展。DNA调控基因的特征 LDH启动子中参与其发育表达的结构域 可能导致将这些领域结合在一起的因素的隔离。这些 对阶段特异性基因表达的研究可能会导致对 抗弓形虫包囊药物设计的潜在靶点 发展或重新激活。

The protozoan pathogen Toxoplasma gondii is a significant cause of disease in humans and in domestic animals. T. gondii can cause acute and often fatal opportunistic infection in patients undergoing immunosuppressive therapy. AIDS patients with a previously latent infection may develop toxoplasmic encephalitis which is a significant cause of morbidity and mortality. IN intermediate host, T. gondii exists in two forms, the tachyzoite and the bradyzoite. During the acute phase of infection, the invasive tachyzoite form predominates and is responsible for tissue destruction. Tachyzoites switch to the bradyzoite form enclosed within tissue cysts which persist during the latent infection even in healthy individuals and patients undergoing current anti-T gondii drug therapies. Reactivation of a previously latent infection resulting from cyst rupture in the brain or other tissue leads to the reemergence of the tachyzoite form and is thought to be the major cause of active toxoplasmosis in AIDS patients. Since tissue cysts are involved in the maintenance of the latent infection and are the source of parasites in reactivation, it is important to study the mechanisms of interconversion between the tachyzoite and bradyzoite stages. In order to study the regulation of stage specific gene expression during conversion, several stage-specific genes were cloned including two with strong homology to lactate dehydrogenase (LDH) from other species. One LDH gene is bradyzoite specific and the other is tachzoite specific. TO study the mechanisms of the stage-specific regulation of these LDH genes, the following approaches will be taken : (1) The profiles of expression of LDH polypeptide will be studied during interconversion of bradyzoites and tachyzoites using in vitro models of differentiation, (2) the transcriptional activity of the LDH2 gene will be studied during stage conversion, (3) the promoter and DNA sequence domains responsible for the developmental transcriptional activation and regulation of the LDH2 gene will be identified by deletional and mutational analysis, and (4) the functional significance of the bradyzoite-specifically expressed LDH isoform will be examined by generating null mutants by gene replacement. Gene replacement studies of the bradyzoite LDH gene will performed to determine its importance to cyst development. Characterization of the DNA regulatory domains in the LDH promoters involved in their development. Characterization of the DNA regulatory domains in the LDH promoters involved in their developmental expression might lead to the isolation of the factors that bind these domains. These studies of stage-specific gene expression might lead to the identification of potential target for anti-T gondii drug design aimed at blocking cyst development or reactivation.