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Primary brain cell infection by Toxoplasma gondii reveals the dynamics of spontaneous bradyzoite differentiation and the extend of modification of neuron biology after infection

ABSTRACT: Toxoplasma gondii is a eukaryotic parasite that form latent cyst in the brain of immunocompetent individuals. The latent parasites infection of the immune privileged central nervous system is linked to most complications. With no drug currently available to eliminate the latent cysts in the brain of infected hosts, the consequences of neurons long-term infection are unknown.. It has long been known that T. gondii specifically differentiate into a latent form (bradyzoite) in neurons, but how the infected neuron is responding to the infection remain to be elucidated. We have established a new in vitro model resulting in the production of fully mature bradyzoites cysts in brain cells. Using dual, host and parasite, RNA-seq we characterized the dynamics of differentiation of the parasite, revealing the involvement of key pathways in this process. Moreover, we identified how the infected brain cells responded to the parasite infection revealing the drastic changes that take place. We showed that neuronal specific pathways are strongly affected, with synapse signaling being particularly affected, especially glutamatergic synapse. The establishment of this new in vitro model allows to investigate both the dynamics of the parasite differentiation and the specific response of neurons to the long term infection by this parasite.

ORGANISM(S): Toxoplasma gondii Rattus norvegicus

PROVIDER: GSE168465 | GEO | 2021/09/23

REPOSITORIES: GEO

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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.

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Primary brain cell infection by Toxoplasma gondii reveals the dynamics of spontaneous bradyzoite differentiation and the extend of modification of neuron biology after infection

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