Project description:The apicomplexan parasite Cryptosporidium is a leading global cause of severe diarrheal disease and an important contributor to early childhood mortality. Currently there are no fully effective treatments or vaccines available. Transmission of the disease occurs through ingestion of oocysts, through direct contact or contaminated water or food. Oocysts are meiotic spores and the product of parasite sex. Cryptosporidium has a single host lifecycle where both asexual and sexual processes unfold in the intestine of infected hosts. Here we use the new-found ability to genetically engineer Cryptosporidium to make life cycle progression and parasite sex tractable. We derive reporter strains to follow parasite development in culture and infected mice and define the genes that orchestrate sex and oocyst formation through mRNA sequencing of sorted cells. After two days, parasites in cell culture show pronounced sexualization, but productive fertilization does not occur and infection falters. In contrast in infected mice, male gametes successfully fertilize females, leading to meiotic division and sporulation. To rigorously test for fertilization, we devised a two-component genetic crossing assay employing a Cre recombinase activated reporter. Our findings suggest obligate developmental progression towards sex in Cryptosporidium, which has important implications for the treatment and prevention of the infection.
Project description:Transcription time course of Plasmodium falciparum parasite asexual blood stage progression in the presence of antimalarial drug CID5750730 (Compound C)
Project description:Kinetochores are multiprotein assemblies that bind chromosomes to the spindle during mitosis. Despite conserved roles, repertoires of kinetochore proteins vary greatly across eukaryotes. In particular, most known components are not clearly detected in a group of parasites known as the Apicomplexa. Furthermore, flexibility in scale of amplification and an apparent incapability to delay cell cycle progression in response to spindle integrity has coined an idea these parasites divide in the absence of spindle checkpoints. In this study, we reunite divergent apicomplexan kinetochore components to a common eukaryotic set and additionally identify 9 kinetochore proteins that share little homology to known proteins. AKiTs are essential for chromosome segregation and show modes of division parallel to eukaryotic metaphase to anaphase transition and spindle assembly checkpoint signaling. These findings suggest conserved spindle assembly checkpoint signaling maintains fidelity during chromosome segregation in apicomplexan parasites.
Project description:Diverse organisms adjust metabolic gene expression during crowding as they encounter nutrient scarcity, oxidative stress, and waste accumulation. Apicomplexan parasites experience these stresses during intracellular growth in host cells, yet lack known regulators of metabolic adaptation. We screened the apicomplexan Toxoplasma gondii to identify genes that support parasite fitness during crowding. NAD(P)+ biosynthesis was required at high parasite density along with several parasite-specific factors, including an RNA-binding protein named T. gondii Parasite Response to Oxidation (TgPRO). TgPRO loss elevated reactive oxygen species under ambient conditions, which was rescued by growth at low oxygen. TgPRO regulates expression of specific transcripts involved in carbon metabolism and iron-sulfur cluster assembly. Regulation of the iron-sulfur cluster assembly protein ISCU relies on TgPRO binding to the transcript’s 3′ UTR. Through convergent evolution, TgPRO performs a role analogous to known metabolic regulators from other species, representing the first dedicated regulator of metabolic gene expression in apicomplexans.
Project description:Apicomplexan parasites cause persistent mortality and morbidity worldwide through diseases including malaria, toxoplasmosis, and cryptosporidiosis. Ca2+ signaling pathways have been repurposed in these eukaryotic pathogens to regulate parasite-specific cellular processes governing the transition between the replicative and lytic phases of the infectious cycle. Despite the presence of conserved Ca2+-responsive proteins, little is known about how specific signaling elements interact to impact pathogenesis. We mapped the Ca2+-responsive proteome of the model apicomplexan T. gondii via time-resolved phosphoproteomics. The waves of phosphoregulation following PKG activation and stimulated Ca2+ release corroborate known physiological changes but identify specific molecular targets in these pathways. We characterized protein phosphatase 1 (PP1) as a Ca2+-responsive enzyme that relocalized to the parasite apex upon Ca2+ store release. Conditional depletion of PP1 revealed that the phosphatase regulates Ca2+ uptake to promote parasite motility. PP1 may thus be partly responsible for Ca2+-regulated serine/threonine phosphatase activity in apicomplexan parasites.
Project description:Apicomplexan parasites cause persistent mortality and morbidity worldwide through diseases including malaria, toxoplasmosis, and cryptosporidiosis. Ca2+ signaling pathways have been repurposed in these eukaryotic pathogens to regulate parasite-specific cellular processes governing the transition between the replicative and lytic phases of the infectious cycle. Despite the presence of conserved Ca2+-responsive proteins, little is known about how specific signaling elements interact to impact pathogenesis. We mapped the Ca2+-responsive proteome of the model apicomplexan T. gondii via time-resolved phosphoproteomics. The waves of phosphoregulation following PKG activation and stimulated Ca2+ release corroborate known physiological changes but identify specific molecular targets in these pathways. We characterized protein phosphatase 1 (PP1) as a Ca2+-responsive enzyme that relocalized to the parasite apex upon Ca2+ store release. Conditional depletion of PP1 revealed that the phosphatase regulates Ca2+ uptake to promote parasite motility. PP1 may thus be partly responsible for Ca2+-regulated serine/threonine phosphatase activity in apicomplexan parasites.
Project description:The experiment investigates bovine gene expression in response to LPS in uninfected and Theileria annulata-infected cell cultures A subset of genes are identified which are activated in response to LPS stimulation with further modulation due to parasite infection. Six experimental conditions with three replicates per condition. Total RNA prepared from cell cultures. BL20 (uninfected bovine lymphosarcoma cell line), BL20 4 hours post-LPS stimulation, BL20 18 hours post-LPS, TBL (T. annulata infected bovine cell line), TBL 4 hours post-LPS, TBL 18 hours post-LPS. Each hydridisation represents bovine and parasite gene expression on a single channel and 2 technical replicates of each probeset are represented on the chip.
Project description:The experiment investigates bovine gene expression in response to LPS in uninfected and Theileria annulata-infected cell cultures A subset of genes are identified which are activated in response to LPS stimulation with further modulation due to parasite infection.