Project description:Developmental regulation of the intracellular parasite Toxoplasma gondii is an understudied topic despite being central for a bid to control its dissemination around the globe. Of particular neglect are the factors that contribute to its sexual development. While it has previously been shown that generalized transcriptional repression machinery plays an important role in silencing spurious gene expression of sexually-committed parasites, the specific factors that target the generalized machinery to genetic loci remains unexplored. Here, we uncover that a member of the AP2 transcription factor family, AP2XII-2, is targeted to genomic loci that are associated with sexually-committed parasites along with the generalized regulators of transcriptional silencing, HDAC3 and MORC. Despite widespread association with gene promoters, AP2XII-2 is required for silencing of relatively few genes. We place two genes associated with sexual development downstream of AP2XII-2 control, transcription factor AP2X-10 and the amino acid hydroxylase AAH1. Dissecting gene regulatory pathways of Toxoplasma sexual development will likely be essential for controlling Toxoplasma dissemination in the future.
Project description:Developmental regulation of the intracellular parasite Toxoplasma gondii is an understudied topic despite being central for a bid to control its dissemination around the globe. Of particular neglect are the factors that contribute to its sexual development. While it has previously been shown that generalized transcriptional repression machinery plays an important role in silencing spurious gene expression of sexually-committed parasites, the specific factors that target the generalized machinery to genetic loci remains unexplored. Here, we uncover that a member of the AP2 transcription factor family, AP2XII-2, is targeted to genomic loci that are associated with sexually-committed parasites along with the generalized regulators of transcriptional silencing, HDAC3 and MORC. Despite widespread association with gene promoters, AP2XII-2 is required for silencing of relatively few genes. We place two genes associated with sexual development downstream of AP2XII-2 control, transcription factor AP2X-10 and the amino acid hydroxylase AAH1. Dissecting gene regulatory pathways of Toxoplasma sexual development will likely be essential for controlling Toxoplasma dissemination in the future.
Project description:Toxoplasma strains have been shown to modulate host cell transcription. We have found a type II Toxoplasma gene, GRA15, which activates the nuclear translocation of the NF-kappaB p65 transcription factor. We used microarrays to determine how GRA15II modulates host cell transcription.
Project description:Toxoplasma strains have been shown to modulate host cell transcription. We have found a type II Toxoplasma gene, GRA15, which activates the nuclear translocation of the NF-kappaB p65 transcription factor. We used microarrays to determine how GRA15II modulates host cell transcription, and whether this transcription is dependent on the p65 transcription factor.
Project description:Toxoplasma gondii is an intracellular parasite with a significant impact on human health, especially in cases where individuals are immunocompromised (e.g., due to HIV/AIDS). In Europe and North America only a few clonal genotypes appear to be responsible for the vast majority of Toxoplasma infections, and these clonotypes have been intensely studied to identify strain-specific phenotypes that may play a role in the manifestation of more severe disease. To identify and genetically map strain-specific differences in gene expression, we have carried out expression quantitative trait locus (eQTL) analysis on Toxoplasma gene expression phenotypes using spotted cDNA microarrays. This led to the identification of 16 Toxoplasma genes that had significant and mappable strain-specific variation in hybridization intensity. While the analysis should identify both cis and trans-mapping hybridization profiles, we only identified loci with strain-specific hybridization differences that are most likely due to differences in the locus itself (i.e., cis-mapping). Interestingly, a larger number of these cis-mapping genes than would be expected by chance encode either confirmed or predicted secreted proteins, many of which are known to localize to the specialized secretory organelles characteristic of members of the phylum Apicomplexa. For 6 of the cis-mapping loci we determined if the strain-specific hybridization differences were due to true transcriptional differences or rather strain-specific differences in hybridization efficiency because of extreme polymorphism and/or deletion, and we found examples of both scenarios. Keywords: eQTL mapping; virulence; Toxoplasma gondii 17 F1 progeny from a cross between a type II parent (PDS) and a type III parent (CTG) were used in RNA hybridizations to identify cis and trans-mapping loci regulating gene expression
Project description:Toxoplasma gondii is an intracellular parasite with a significant impact on human health, especially in cases where individuals are immunocompromised (e.g., due to HIV/AIDS). In Europe and North America only a few clonal genotypes appear to be responsible for the vast majority of Toxoplasma infections, and these clonotypes have been intensely studied to identify strain-specific phenotypes that may play a role in the manifestation of more severe disease. To identify and genetically map strain-specific differences in gene expression, we have carried out expression quantitative trait locus (eQTL) analysis on Toxoplasma gene expression phenotypes using spotted cDNA microarrays. This led to the identification of 16 Toxoplasma genes that had significant and mappable strain-specific variation in hybridization intensity. While the analysis should identify both cis and trans-mapping hybridization profiles, we only identified loci with strain-specific hybridization differences that are most likely due to differences in the locus itself (i.e., cis-mapping). Interestingly, a larger number of these cis-mapping genes than would be expected by chance encode either confirmed or predicted secreted proteins, many of which are known to localize to the specialized secretory organelles characteristic of members of the phylum Apicomplexa. For 6 of the cis-mapping loci we determined if the strain-specific hybridization differences were due to true transcriptional differences or rather strain-specific differences in hybridization efficiency because of extreme polymorphism and/or deletion, and we found examples of both scenarios. Keywords: eQTL mapping; virulence; Toxoplasma gondii 19 F1 progeny from a cross between a type II parent (PDS) and a type III parent (CTG) were used in RNA hybridizations to identify cis and trans-mapping loci regulating gene expression
Project description:Toxoplasma gondii is an obligate intracellular parasite that can cause serious opportunistic disease in the immunocompromised or through congenital infection. To progress through its life cycle, Toxoplasma relies on multiple layers of gene regulation that includes an array of transcription and epigenetic factors. Over the last decade, the modification of mRNA has emerged as another important layer of gene regulation called epitranscriptomics. Here, we report that epitranscriptomics machinery exists in Toxoplasma, namely the methylation of adenosines (m6A) in mRNA transcripts. We identified novel components of the m6A methyltransferase complex and determined the distribution of m6A marks within the parasite transcriptome. m6A mapping revealed the modification to be preferentially located near transcription termination sites within the consensus sequence, YGCAUGCR. Knockdown of the m6A writer enzyme METTL3 resulted in diminished m6A marks, loss of a target transcript, and a complete arrest of parasite replication. Furthermore, we examined the two proteins in Toxoplasma that possess YTH domains, which bind m6A marks, finding them to be integral members of the cleavage and polyadenylation machinery that catalyzes the 3’-end processing of pre-mRNAs. Together, these findings establish that the m6A epitranscriptome is essential for parasite viability by contributing to the processing of mRNA 3’-ends.