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: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.
Project description:This SuperSeries is composed of the following subset Series: GSE11437: Expression QTL mapping of Toxoplasma gondii genes, Bradyzoite array GSE11514: Expression QTL mapping of Toxoplasma gondii genes, Tachyzoite array Keywords: SuperSeries Refer to individual Series
Project description:Cyst formation is a key feature of the T. gondii life cycle but the genetic networks that drive this process are not yet fully characterized. To identify new components of this network, we compared T. gondii to its nearest extant relative Hammondia hammondi given the critical differences between these species in the timing and efficiency of cyst formation. Using transcriptional data from critical developmental and pH exposure time points from both species, we identified the gene TGVEG_311100, which we named Regulator of Cystogenesis 1 (ROCY1), as being both necessary and sufficient for cyst formation in T. gondii. Compared to WT parasites, TGVEG?ROCY1 parasites formed significantly fewer tissue cysts in response to alkaline pH stress in vitro and cysts were nearly undetectable in mouse brains for up to 9 weeks post-infection. Overexpression of tagged ROCY1 in WT parasites was sufficient to induce cyst formation in vitro in both WT and ROCY1-deficient parasites, demonstrating that ROCY1 is both necessary and sufficient for cyst formation. Moreover this induction of cyst formation required at least 1 of 3 predicted CCCH Zinc finger domains. Mice chronically infected with ?ROCY1 parasites had detectable tachyzoites in the brain for up to 37 days post-infection (while mice infected with WT parasites did not), and CNS transcriptional analyses at day 30 post-infection throughout the chronic phase of infection revealed inflammatory signatures consistent with acute infection in ?ROCY1 parasites compared to WT. Despite our inability to detect brain cysts in infected mice, both WT and ?ROCY1 knockout parasites reactivated after dexamethasone treatment with similar timing and magnitude for up to 5 months post infection, challenging the paradigm that long term parasite persistence in the CNS requires cyst formation. These data identify a new regulator of cyst formation in T. gondii that is both necessary and sufficient for cyst formation, and whose function relies on its conserved nucleic acid binding motif.