Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
University of Basel, Basel, Switzerland.
mSphere. 2024 Nov 21;9(11):e0054624. doi: 10.1128/msphere.00546-24. Epub 2024 Oct 24.
The malaria parasite employs antigenic variation of the virulence factor erythrocyte membrane protein 1 (PfEMP1) to escape adaptive immune responses during blood infection. Antigenic variation of PfEMP1 occurs through epigenetic switches in the mutually exclusive expression of individual members of the multi-copy gene family. genes are located in perinuclear clusters of transcriptionally inactive heterochromatin. Singular gene activation is linked to locus repositioning into a dedicated zone at the nuclear periphery and deposition of histone 3 lysine 4 di-/trimethylation (H3K4me2/3) and H3K9 acetylation marks in the promoter region. While previous work identified the putative H3K4-specific methyltransferase PfSET10 as an essential enzyme and positive regulator of gene expression, a recent study reported conflicting data. Here, we used iterative genome editing to engineer a conditional PfSET10 knockout line tailored to study the function of PfSET10 in gene regulation. We demonstrate that PfSET10 is not required for mutually exclusive gene expression and switching. We also show that PfSET10 is dispensable not only for asexual parasite proliferation but also for sexual conversion and gametocyte differentiation. Furthermore, comparative RNA-seq experiments revealed that PfSET10 plays no obvious role in regulating gene expression during asexual parasite development and gametocytogenesis. Interestingly, however, PfSET10 shows different subnuclear localization patterns in asexual and sexual stage parasites and female-specific expression in mature gametocytes. In summary, our work confirms in detail that PfSET10 is not involved in regulating gene expression and is not required for blood-stage parasite viability, indicating PfSET10 may be important for life cycle progression in the mosquito vector or during liver stage development.IMPORTANCEThe malaria parasite infects hundreds of millions of people every year. To survive and proliferate in the human bloodstream, the parasites need to escape recognition by the host's immune system. To achieve this, can change the expression of surface antigens a process called antigenic variation. This fascinating survival strategy is based on infrequent switches in the expression of single members of the multigene family. Previous research reported conflicting results on the role of the epigenetic regulator PfSET10 in controlling mutually exclusive gene expression and switching. Here, we unequivocally demonstrate that PfSET10 is neither required for antigenic variation nor the expression of any other proteins during blood-stage infection. This information is critical in directing our attention toward exploring alternative molecular mechanisms underlying the control of antigenic variation and investigating the function of PfSET10 in other life cycle stages.
疟原虫利用毒力因子红细胞膜蛋白 1（PfEMP1）的抗原变异来逃避血液感染期间适应性免疫反应。PfEMP1 的抗原变异通过多拷贝基因家族中个体成员的表观遗传开关发生。基因位于转录失活异染色质的核周簇中。单个基因的激活与基因座重新定位到核周的专用区域以及组蛋白 3 赖氨酸 4 二/三甲基化（H3K4me2/3）和 H3K9 乙酰化标记在启动子区域的沉积有关。虽然之前的工作确定了假定的 H3K4 特异性甲基转移酶 PfSET10 是基因表达的必需酶和正调节剂，但最近的一项研究报告了相互矛盾的数据。在这里，我们使用迭代基因组编辑来设计一种条件性 PfSET10 敲除系，专门用于研究 PfSET10 在基因调控中的功能。我们证明 PfSET10 对于相互排斥的基因表达和转换不是必需的。我们还表明，PfSET10 不仅对无性寄生虫增殖而且对有性转换和配子体分化都是可有可无的。此外，比较 RNA-seq 实验表明，PfSET10 在无性寄生虫发育和配子体发生过程中基因表达的调控中没有明显作用。有趣的是，然而，PfSET10 在无性和有性阶段寄生虫中的亚核定位模式不同，并且在成熟配子体中雌性特异性表达。总之，我们的工作详细证实 PfSET10 不参与调节基因表达，也不需要血液阶段寄生虫的存活，表明 PfSET10 可能对蚊子媒介中的生命周期进展或肝期发育很重要。
重要性
疟原虫每年感染数亿人。为了在人体血液中存活和增殖，寄生虫需要逃避宿主免疫系统的识别。为了实现这一目标，疟原虫可以改变表面抗原的表达，这一过程称为抗原变异。这种迷人的生存策略基于单基因家族中单个成员的罕见表达开关。先前的研究报告了关于表观遗传调节剂 PfSET10 在控制相互排斥的基因表达和转换中的作用的相互矛盾的结果。在这里，我们毫不含糊地证明 PfSET10 既不需要抗原变异，也不需要血液感染期间任何其他蛋白质的表达。这一信息对于指导我们的注意力至关重要，使我们能够探索控制抗原变异的替代分子机制，并研究 PfSET10 在其他生命周期阶段的功能。
