A positive feedback loop controls Toxoplasma chronic differentiation.

Area of Science:

• Molecular Parasitology
• Host-Pathogen Interactions
• Gene Regulation

Background:

• Toxoplasma gondii, an obligate intracellular parasite, establishes chronic infections by differentiating into immune-evasive cyst stages.
• The transcription factor BFD1 is crucial for this stage conversion, but its regulatory mechanisms remain unclear.

Purpose of the Study:

• To investigate the regulation of BFD1 and identify factors involved in Toxoplasma gondii chronic stage differentiation.
• To elucidate the role of a novel RNA-binding protein, BFD2, in parasite persistence.

Main Methods:

• Analysis of genes transcriptionally activated by BFD1.
• Gene deletion studies of BFD2 in Toxoplasma gondii.
• Investigation of BFD2 interaction with BFD1 transcript under stress conditions.
• Assessment of BFD1 protein and mRNA levels in BFD2-deficient parasites.

Main Results:

• Identified bradyzoite formation deficient 2 (BFD2), a CCCH-type zinc-finger RNA-binding protein, as a BFD1 target.
• BFD2-deficient parasites exhibit impaired BFD1 induction and incomplete differentiation in vitro and in vivo.
• BFD2 deletion reduces BFD1 protein levels without affecting its mRNA abundance, suggesting translational regulation.
• A positive feedback loop between BFD2 transcription and BFD1 translation enforces chronic stage gene expression.

Conclusions:

• BFD2 is essential for initiating and committing Toxoplasma gondii to chronic differentiation.
• The BFD2-BFD1 regulatory axis provides mechanistic insight into parasite persistence.
• This pathway represents a potential target for developing strategies to combat Toxoplasma gondii infections.