In Vivo and In Vitro Characterization of a Plasmodium Liver Stage-Specific Promoter

Little is known about stage-specific gene regulation in Plasmodium parasites, in particular the liver stage of development. We have previously described in the Plasmodium berghei rodent model, a liver stage-specific (lisp2) gene promoter region, in vitro. Using a dual luminescence system, we now confirm the stage specificity of this promoter region also in vivo. Furthermore, by substitution and deletion analyses we have extended our in vitro characterization of important elements within the promoter region. Importantly, the dual luminescence system allows analyzing promoter constructs avoiding mouse-consuming cloning procedures of transgenic parasites. This makes extensive mutation and deletion studies a reasonable approach also in the malaria mouse model. Stage-specific expression constructs and parasite lines are extremely valuable tools for research on Plasmodium liver stage biology. Such reporter lines offer a promising opportunity for assessment of liver stage drugs, characterization of genetically attenuated parasites and liver stage-specific vaccines both in vivo and in vitro, and may be key for the generation of inducible systems.

目前学界对疟原虫（Plasmodium）各发育阶段的特异性基因调控机制知之甚少，尤其是其肝脏发育阶段的调控过程。本研究团队此前在啮齿类疟疾模型伯氏疟原虫（Plasmodium berghei）中，体外鉴定出一个肝脏阶段特异性的lisp2基因启动子区域。本次研究借助双发光检测系统（dual luminescence system），在体内同样验证了该启动子区域的阶段特异性。此外，通过替换与缺失分析，我们进一步拓展了对该启动子区域内关键调控元件的体外表征工作。尤为重要的是，双发光检测系统可用于分析启动子构建体，无需开展耗费实验动物的转基因寄生虫克隆操作，这使得大规模突变与缺失分析研究在疟疾小鼠模型中也具备了可行性。阶段特异性表达构建体与寄生虫细胞系，是疟原虫肝脏阶段生物学研究的极有价值的工具。此类报告细胞系可为肝脏阶段药物评估、基因减毒寄生虫（genetically attenuated parasites）表征以及肝脏阶段特异性疫苗的体内外鉴定提供极具前景的研究途径，同时也可能成为构建诱导型系统（inducible systems）的关键技术基础。