Investigating mechanisms of chromosome segregation during the exit of male Plasmodium gametes.

疟原虫是疟疾的病原体，它有一个复杂的、主要在细胞内的生命周期，在脊椎动物和蚊子宿主之间交替。为了从一个阶段进入下一个阶段，这些寄生虫制定了不同的离开宿主细胞的策略。最复杂和最快速的策略之一发生在蚊子感染的早期，当时性配子细胞离开宿主细胞形成配子。在雄配子发生过程中，宿主细胞的裂解与从单个配子体快速形成8个有鞭毛的雄配子的过程同时发生，这是一个高度有序但鲜为人知的过程。在短时间内，激活的雄配子体复制其DNA三次，而不进行核分裂。只有当八个鞭毛开始活动，配子离开残余体时，它们才会拉出一个核，其中包括与它们一起设置的染色体。作为SPP-2225退出的一部分，我们想要阐明雄配子确保他们在退出时携带一套完整的染色体的分子机制。到目前为止，我们已经确定ARC40蛋白是形成有功能的雄配子所必需的。当ARC40在啮齿动物寄生虫伯氏疟原虫中被敲除时，雄配子的DNA含量减少，寄生虫不再能成功感染蚊子。因此，ARC40对于将完整的染色体组分离到现存的雄配子中是重要的。然而，ARC40的作用模式和这一过程的机制细节仍不清楚。由于WD40蛋白质经常介导蛋白质-蛋白质相互作用，我们假设ARC40作为一个更大的蛋白质复合体的支架，在染色体退出时将染色体连接到配子。我们的目标是通过识别与ARC40相互作用的蛋白质来表征这种蛋白质复合体。此外，我们想要研究染色体分离的机制在人类感染物种恶性疟原虫中是否保守。ARC40已被注释为肌动蛋白调节蛋白，几项已发表的研究表明，核肌动蛋白在多种生物的染色体分离中发挥作用。因此，在我们的最终目标中，我们的目标是研究核肌动蛋白在疟原虫配子染色体分裂中的作用。在这里，我们特别关注一种特定于疟原虫的肌动蛋白亚型，这种同型蛋白专门存在于雄配子细胞中。实现这三个目标将揭示疟原虫在雄配子退出过程中如何协调DNA分离与细胞分裂的新机制。如果ARC40对恶性疟原虫的感染也是必不可少的，这些机制可能成为一个有希望的新药靶点。

Plasmodium parasites, the causative agents of malaria, have a complex, mostly intracellular life cycle that alternates between a vertebrate and a mosquito host. To move from one stage to the next, these parasites have developed different strategies to leave their host cell. One of the most complex and rapid strategies occurs during early mosquito infection when sexual gametocytes leave their host cell and form gametes. During male gametogenesis, host cell lysis occurs in parallel with the rapid formation of eight flagellated male gametes from a single gametocyte in a highly ordered but poorly understood process. Within a short period of time, the activated male gametocyte replicates its DNA three times without the nucleus dividing. Only when the eight flagella become mobile and the gametes leave the residual body, do they pull a nucleus including the chromosome set with them. As part of the SPP-2225 Exit, we want to elucidate the molecular mechanisms by which the male gametes ensure that they take a complete set of chromosomes with them when they exit. So far, we have identified the protein ARC40 as essential for the formation of functional male gametes. When ARC40 is knocked out in the rodent parasite Plasmodium berghei, male gametes have a reduced DNA content and parasites can no longer successfully infect mosquitoes. ARC40 is thus important to segregate complete chromosome sets into the exiting male gametes. However, the mode of action of ARC40 and the mechanistic details of this process remain unclear. Since WD40 proteins often mediate protein-protein interactions, we hypothesise that ARC40 acts as a scaffold for a larger protein complex that connects chromosomes to gametes during their exit. Our goal is to characterise this protein complex by identifying the proteins that interact with ARC40. Furthermore, we want to investigate whether the mechanisms of chromosome segregation are conserved in the human-infecting species Plasmodium falciparum. ARC40 has been annotated as an actin-regulatory protein, and several published studies indicate a role for nuclear actin in chromosome segregation in a variety of organisms. In our final objective, we therefore aim to investigate the role of nuclear actin in Plasmodium gamete chromosome division. Here we focus in particular on a Plasmodium-specific actin isotype that is specifically present in male gametocytes. Fulfilling these three objectives will reveal new mechanisms for how Plasmodium coordinates DNA segregation with cell division during male gamete exit. If ARC40 is also essential for P. falciparum infection, these mechanisms could be a promising new drug target.