Project description:Using high through-put RNA sequencing, we assayed the transcriptomes of three different strains of Toxoplasma gondii representing three common genotypes under both in vitro tachyzoite and in vitro bradyzoite-inducing alkaline stress culture conditions. Strikingly, the differences in transcriptional profiles between the strains, RH, PLK, and CTG, is much greater than differences between tachyzoites and alkaline stressed in vitro bradyzoites. With an FDR of 10%, we identify 241 genes differentially expressed between CTG tachyzoites and in vitro bradyzoites, including 5 putative AP2 transcription factors. We also observe close association between cell cycle regulated genes and differentiation. By Gene Set Enrichment Analysis (GSEA), there are a number of KEGG pathways associated with the in vitro bradyzoite transcriptomes of PLK and CTG, including pyrimidine metabolism and DNA replication. These functions are likely associated with cell-cycle arrest. When comparing mRNA levels between strains, we identify 1,526 genes that are differentially expressed regardless of culture-condition as well as 846 differentially expressed only in bradyzoites and 542 differentially expressed only in tachyzoites between at least two strains. Using GSEA, we identify ribosomal proteins as being expressed at significantly higher levels in the CTG strain than in either the RH or PLK strains. This association holds true regardless of life cycle stage. Type I M-bM-^@M-^S RH, Type II M-bM-^@M-^S PLK, and Type III CTG parasites were each grown in either alkaline, bradyzoite conditions or pH neutral, tachyzoites conditions. 6 conditions, 3 replicates each, 18 total samples
Project description:Using high through-put RNA sequencing, we assayed the transcriptomes of three different strains of Toxoplasma gondii representing three common genotypes under both in vitro tachyzoite and in vitro bradyzoite-inducing alkaline stress culture conditions. Strikingly, the differences in transcriptional profiles between the strains, RH, PLK, and CTG, is much greater than differences between tachyzoites and alkaline stressed in vitro bradyzoites. With an FDR of 10%, we identify 241 genes differentially expressed between CTG tachyzoites and in vitro bradyzoites, including 5 putative AP2 transcription factors. We also observe close association between cell cycle regulated genes and differentiation. By Gene Set Enrichment Analysis (GSEA), there are a number of KEGG pathways associated with the in vitro bradyzoite transcriptomes of PLK and CTG, including pyrimidine metabolism and DNA replication. These functions are likely associated with cell-cycle arrest. When comparing mRNA levels between strains, we identify 1,526 genes that are differentially expressed regardless of culture-condition as well as 846 differentially expressed only in bradyzoites and 542 differentially expressed only in tachyzoites between at least two strains. Using GSEA, we identify ribosomal proteins as being expressed at significantly higher levels in the CTG strain than in either the RH or PLK strains. This association holds true regardless of life cycle stage.
Project description:The Toxoplasma gondii G1 RESTRICTION checkpoint operates the switch between parasite growth and differentiation. The Cdk-related G1 kinase TgCrk2 forms alternative complexes with atypical cyclins (TgCycP1, TgCycP2 and TgCyc5) in the rapidly dividing developmentally incompetent RH and slower dividing developmentally competent ME49 tachyzoites and bradyzoites. The TgCycP1 expression interferes with bradyzoite differentiation. The TgCycP2 regulates G1 in the developmentally competent ME49 but not in the developmentally incompetent RH tachyzoites. Examination of TgCycP2 and TgCyc5 in alkaline induced and spontaneous bradyzoite differentiation (rat embryonic brain cells) models confirmed TgCycP2 role in bradyzoite replication and revealed that stress induced TgCyc5 is critical for efficient tissue cyst maturation.
Project description:Toxoplasma gondii is a globally distributed obligate intracellular parasite which can cause zoonotic toxoplasmosis with great harms. The average death time of mice that infected with Toxoplasma gondii RH strain tachyzoites recovered from the liquid nitrogen was shortened after multiple generations. It has been reported that the parasite is in a state of static virulence during cryopreservation and the virulence of the protozoan parasite can be enhanced after continuous passages in hosts under laboratory conditions. However, no research has been conducted to elucidate its biological mechanism. Herein, we sequenced the T. gondii transcriptome using RNA-Seq technology and performed de novo assembly to investigated the virulence factors expression changes by comparing gene expression profiles between incipiently recovered and completely resuscitated tachyzoites. Transcriptome analysis identified 1,951 differentially expressed transcripts in infected liver, of which 1,752 were significantly downregulated and 199 upregulated. We identified many differentially expressed proteins and genes, including serine/threonine kinase, calnexin, myosin and microtubule-associated protein which have previously been reported to be either involved in cell adhesion, parasite gliding or participate in cell invasion. The great majority of the virulence factors including microneme proteins, rhoptry proteins and dense granule proteins were upregulated in fully recovered tachyzoites. The enhanced virulence of recovered Toxoplasma gondii RH strain from the liquid nitrogen is associated with the up-regulated expression of MICs, ROPs and GRAs. Our data will facilitate future genomic research and in-depth annotation of Toxoplasma gondii RH strain genomes. This study provides a profile of the candidate genes that are suspected to be involved with virulence enhancement of recovered Toxoplasma gondii RH strain tachyzoites. Many further studies should be carried out to confirm the function of the candidate genes. Moreover, the preliminary identification of genes and pathways exhibiting differential expression in complete resuscitation stage may further our general understanding of virulence enhancement in this parasite.
Project description:The lack of a comprehensive map of transcription start sites in Toxoplasma gondii has impeded advances in decrypting the molecular mechanisms underlying the regulation of gene expression. Genome-wide approaches for mapping transcription initiation have been instrumental in defining the determinants of transcription initiation in a range of model eukaryotes. We used a protocol for 5′-end RNA sequencing, called RAMPAGE, to sequence the 5′-ends of capped mRNA from ME49 and RH tachyzoites, as well as from ME49 bradyzoites. This allowed us to generate maps of transcription initiation events at single-nucleotide resolution across the asexual stages of the parasite.
Project description:MOB1 is a conserved protein that regulates cellular proliferation versus apoptosis, centrosome duplication and cellular differentiation in multicellular eukaryotes and also cytokinesis and division axis orientation in unicellular and multicellular eukaryotes. Toxoplasma gondii, an obligate intracellular parasite of veterinary and medical importance, presents one MOB1 protein. T. gondii interconverts between several cellular stages during its life cycle, namely between fast replicating tachyzoite and slow replicating bradyzoite stages during its asexual cycle, a key ability for its success as a parasite. Bradyzoites produce tissue cysts, establishing a chronic infection that enables recrudescence. Conversion is dependent on cell cycle regulation and involves cell differentiation and regulation of replication. This led us to select MOB1 as a strong candidate to be involved in the Toxoplasma replication process. To elucidate how MOB1 acts in T. gondii, we employed a proximity biotinylation method and identified the MOB1 interactome. Toxoplasma gondii RH tachyzoites were transfected with BirA containing plasmid vectors for random integration and two strains were isolated. The control strain expresses a FLAG-BirA recombinant protein while the test strain expresses a FLAG-BirA-MOB1 recombinant protein. Biotinylated proteins were purified using streptavidin-agarose beads. The purified proteins were trypsinized and analyzed by nanoLC-MS/MS.
Project description:The in vitro effect of infection with different strains of Toxoplasma gondii was tested 24 hours after infection of Human Foreskin Fibroblasts (HFF) The strains tested include RH, VEG, and transgenic strains of RH overexpressing ROP38 or ROP21 Total RNA of Toxoplasma gondii infected HFF cell was compared to uninfected cells
Project description:The in vitro effect of infection with different strains of Toxoplasma gondii was tested 24 hours after infection of Human Foreskin Fibroblasts (HFF) The strains tested include RH, VEG, and transgenic strains of RH overexpressing ROP38 or ROP21
Project description:Although apicomplexans lack conventional R-point regulators, presence of the quiescent G1 forms of 43 parasites, including mature T. gondii bradyzoites suggests that a functional RESTRICTION checkpoint 44 exists in apicomplexan parasites. We showed that Cdk-related G1 kinase TgCrk2 forms alternative 45 complexes with atypical cyclins (TgCycP1, TgCycP2 and TgCyc5) in the rapidly dividing developmentally 46 incompetent RH and slower dividing developmentally competent ME49 tachyzoites and bradyzoites. 47 Examination of individual cyclins verified the correlation of cyclin expression with growth dependence and 48 development capacity of type I RH and type II ME49 strains. We demonstrated that rapidly dividing RH 49 tachyzoites are dependent on TgCycP1 and expression of TgCycP1 interferes with bradyzoite 50 differentiation. By using an auxin-induced degradation (AID) model, we established that TgCycP2 51 regulates G1 duration in the developmentally competent ME49 tachyzoites but not in the developmentally 52 incompetent RH tachyzoites. We also tested the functions of TgCycP2 and TgCyc5 in alkaline induced in 53 vitro model and in ex vivo model of spontaneous bradyzoite differentiation (rat embryonic brain cells). 54 Based on functional and global gene expression analyses, we determined that TgCycP2 also regulates 55 bradyzoite replication, while stress- or host-induced TgCyc5 was critical for efficient bradyzoite conversion 56 and tissue cyst maturation.
Project description:Recent advances in high throughput sequencing methodologies allow the opportunity to probe in depth the transcriptomes of organisms including N. caninum and Toxoplasma gondii. In this project, we are using Illumina sequencing technology to analyze the transcriptome (RNA-Seq) of experimentally accessible stages (e.g. tachyzoites at different times points) of T. gondii VEG strain. The aim is to make comparative transcriptional landscape maps of Neospora and Toxoplasma at different time points at different life cycle stages and compare levels of expression of orthologous genes in these two organisms.