Functional dissection of Condensin and Cohesin in atypical mitosis and meiosis in Plasmodium

疟原虫是疟疾的病原体，每年造成约58.4万人死亡，其中大部分是5岁以下的儿童。这种寄生虫对现有药物的抗药性日益增强，以及缺乏有效的疫苗，是消除这一负担的主要障碍。因此，迫切需要发展创新疗法。疟原虫具有复杂的生活史，寄主环境多种多样，细胞形态、大小和运动能力发生变化，细胞增殖方式不典型。当疟疾寄生虫入侵宿主红细胞时，这种疾病的症状就会显现出来，其中寄生虫会分裂并多次繁殖(内丝分裂)，最终导致宿主细胞的破坏。一些寄生虫细胞可能停止分裂，成为前驱性细胞(雄配子体和雌配子体)。当雌性蚊子叮咬感染者时，它们会与血液一起摄入寄生虫，这就触发了蚊子肠道内的前体性细胞。雄配子体经历快速的细胞分裂(内复制)，产生8个雄配子，然后使雌配子受精，寄生虫的生命周期在蚊子的肠道中继续。在进一步发展和繁殖后，寄生虫移动到蚊子的唾液腺，并在蚊子进食时再次传递给新的人类宿主。疟原虫在宿主红细胞中的细胞分裂过程与蚊媒中的性发育过程截然不同，但两者都是寄生虫生长和传播的关键。如果这些阶段中的任何一个被阻止，那么扩散和传播都将受到限制。因此，了解寄生虫在这些阶段是如何繁殖和分裂的至关重要，这样我们就可以设计出通过开发适当的药物来干扰它们的方法。在寄生虫中控制这些类型的非典型细胞分裂的分子知之甚少。这里提出的项目是研究两种重要的蛋白质复合体：凝集素和粘附素的作用。尽管已知这些复合体参与了许多模型系统的细胞分裂，但尚不清楚它们在疟疾寄生虫细胞分裂和增殖过程中的作用。我们可以首先利用在模型系统中收集的知识，并将其应用于疟疾寄生虫。例如，我们最近在疟疾寄生虫中发现了一种这样的蛋白质(CDC20)，并表明它在调节雄配子形成方面具有关键作用。在表明我们的方法是可行的初步工作中，我们已经获得了在红血球内繁殖的寄生虫、在雄性性细胞和减数分裂细胞(动细胞)中存在凝聚素和粘附素的证据。最近在分析疟疾基因方面的进展使我们能够研究这些分子的功能。例如，通过去除基因，我们可以看到当蛋白质不再制造时会发生什么，如果我们在实验中用荧光标记器标记它们，我们可以在显微镜下看到它们在寄生虫中的位置。我们还将研究这些分子在染色体分离和胞质分裂等不同过程中如何与其他蛋白质相互作用，仅举两例。我们还可以提纯这些蛋白质复合体，并用基于质谱学的方法研究它们之间的相互作用。因此，我们现在可以探索这些复合体如何控制疟疾的细胞分裂，我们可以研究这些分子如何调节细胞分裂的不同阶段。我们的研究可能会识别宿主红细胞和蚊子媒介内分裂细胞中对寄生虫细胞分裂重要的分子靶标。因此，我们可能会确定药物或疫苗的潜在目标，这些药物或疫苗未来可能被用来阻止寄生虫在血液中的复制，并通过蚊子从一个人传播到另一个人。

Plasmodium is the causative agent of malaria and is responsible for about 584,000 human deaths annually, mostly children under the age of 5. The increasing resistance of the parasite to existing drugs and the lack of an efficient vaccine represent the main obstacles to combat this burden. Therefore, there is an urgent need for the development of innovative therapeutics. Plasmodium has a complex life cycle with diverse host environments, changes in cell shape, size and motility and an atypical mode of cell proliferation. The symptoms of the disease are manifest when malaria parasites invade host red blood cells, wherein the parasite divides and multiplies many times (endomitosis), eventually leading to destruction of the host cell. Some of the parasite cells may cease to divide and they become precursor sex cells (male and female gametocytes). When a female mosquito bites an infected person they ingest parasites along with the blood and this acts as a trigger to activate the precursor sex cells within the mosquito gut. The male gametocytes undergo rapid cell division (endoreduplication) to produce eight male gametes, which then fertilise the female gametes and the parasite life cycle continues in the mosquito gut. After further development and multiplication the parasite moves to the mosquito's salivary glands and is passed again to a new human host when the mosquito feeds.The process of Plasmodium cell division in host red blood cells, and during sexual development in the mosquito vector is very different, but both are essential for parasite growth and transmission. If any of these stages are blocked then both proliferation and transmission are curtailed. Therefore, it is critically important to understand how the parasite multiplies and divides at these stages so that we can devise ways to interfere with them by developing appropriate drugs. The molecules that control these types of atypical cell division in the parasite are very poorly understood. The project proposed here is to study the role of two important protein complexes: condensin and cohesin. Although these complexes are known to be involved in cell division in many model systems, there is no knowledge of how they function during malaria parasite cell division and proliferation. We can start by using the knowledge gathered in model systems and applying this to the malaria parasite. For example, we have recently identified one such protein (CDC20) in the malaria parasite and showed that it has a key role in regulating male gamete formation. In preliminary work showing that our approach is feasible, we have obtained evidence for the presence of condensin and cohesin in the parasite multiplying within the red blood cell, in the male sex cell and in the meiotic cell (an ookinete). Recent advances in analysing genes in malaria allow us to study the function of these molecules. For example, by taking away the gene, we can see what happens when the proteins are no longer made, and if they are tagged experimentally with a fluorescent marker we can see under the microscope where they are located in the parasite. We will also study how these molecules interact with other proteins during various processes such as chromosome segregation and cytokinesis, to name two. We can also purify these protein complexes and study their interactions using mass spectroscopy-based approaches. Therefore, we are now in a position where we can explore how cell division in malaria is controlled by these complexes and we can study how these molecules regulate different stages of cell division.Our study may identify molecular targets important in parasite cell division in host red blood cells and in the cells dividing within the mosquito vector. As a result, we may identify potential targets for drugs or vaccines that could in the future be used to block parasite replication in the blood and transmission from one individual to another through the mosquito.