CHARACTERIZATION OF THE ROLE OF UIS12 IN PLASMODIUM YOELII MALE GAMETOCYTE ACTIVATION

Open Access
Author:
Vrana, Erin Nicole
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Scott E. Lindner, Thesis Supervisor
  • Sarah Ades, Honors Advisor
Keywords:
  • malaria
  • Plasmodium yoelii
  • UIS12
  • translational repression
  • Biochemistry and Molecular Biology
Abstract:
Malaria is a daunting public health concern worldwide, with over 200 million infections per year and over 438,000 deaths in 2015 alone. A top priority in malaria research is the development of an effective vaccine that can be administered to high-risk populations. Currently, the most promising approaches in vaccine development target gene products that are important to the sporozoite and liver stages of the parasite’s life cycle, as these stages are essential for initiation of the malarial infection. A class of malarial genes known as UIS (Up-regulated in Infectious Sporozoites) has been identified as a target for this type of vaccine development. One of these genes, UIS12, shows promise as being important to parasite transmission: it is an RNA-binding protein and is translationally repressed in salivary gland sporozoites. Transmission of the parasite is regulated by translational repression, and RNA-binding proteins are central to this regulation mechanism. We hypothesized that UIS12 is integral to parasite transmission, and to address this, we produced transgenic Plasmodium yoelii parasites with a genetic disruption of the UIS12 gene (pyuis12-), as well as parasites with the intact UIS12 protein labeled with a Green Fluorescent Protein tag (UIS12::GFP). By visualizing UIS12::GFP throughout the parasite’s life cycle using live fluorescence and immunofluorescence assays (IFAs), we determined that UIS12 protein is present in all stages of the parasite life cycle except for salivary gland sporozoites, where it is known to be translationally repressed. Experiments using the pyuis12- parasites demonstrated that, while asexual blood stage growth kinetics were unaffected compared to wild-type parasites, the pyuis12- parasites showed a roughly 30- to 50-fold decrease in quantifiable male gametocyte exflagellation (projection of flagella to detect female gametocytes) as compared to wild-type parasites on the peak day of exflagellation. Moreover, these parasites could not be transmitted from host to mosquitoes, as no oocysts formed in mosquito midguts when pyuis12- gametocytes were fed to mosquitoes. To further investigate the role of UIS12 in transmission, we intend to characterize the protein composition of the UIS12 complex in the transmitted sexual stage of the malaria parasite, by immunoprecipitating UIS12 and identifying binding partners using nano LC/MS/MS. In conclusion, these studies suggest that UIS12 plays a key role in sexual stage development and may prove to be a valuable target in interrupting the transmission of the malaria parasite.