In vitroproduction of cat-restrictedToxoplasmapre-sexual stages by epigenetic reprogramming

Abstract

Summary paragraphSexual reproduction ofToxoplasma gondii, which is restricted to the small intestine of felids, is sparsely documented, due to ethical concerns surrounding the use of cats as model organisms. Chromatin modifiers dictate the developmental fate of the parasite during its multistage life cycle, but their targeting to stage-specific cistromes is poorly described1. In this study, we found that transcription factors AP2XII-1 and AP2XI-2, expressed in tachyzoite stage that causes acute toxoplasmosis, can silence genes necessary for merozoites, a developmental stage critical for sexual commitment and transmission to the next host, including humans. Their conditional and simultaneous depletion leads to a drastic change in the transcriptional program, promoting a complete transition from tachyzoites to merozoites. Pre-gametes producedin vitrounder these conditions are characterized by specific protein markers and undergo typical asexual endopolygenic division cycles. In tachyzoites, AP2XII-1 and AP2XI-2 bind DNA as heterodimers at merozoite promoters and recruit the epigenitors MORC and HDAC31, which in turn restrict the accessibility of chromatin to the transcriptional machinery. Thus, the commitment to merogony stems from a profound epigenetic rewiring orchestrated by AP2XII-1 and AP2XI-2. This effectivein vitroculture of merozoites paves the way to exploreToxoplasmasexual reproduction without the need to infect kittens and has potential for the development of therapeutics to block parasite transmission.

APlasmodium falciparumMORC protein complex modulates epigenetic control of gene expression through interaction with heterochromatin

“…Pf EELM2 was previously predicted as a Pf MORC interactor (Hillier et al 2019) and identified in a quantitative histone peptide pulldown to be consistently recruited to H2B.Z_K13/14/18a (Hoeijmakers et al 2019). Furthermore, we also detected numerous ApiAP2 transcription factors [ Pf AP2-G5, Pf AP2-O5, Pf AP2-I, PF3D7_1107800, PF3D7_0613800, PF3D7_0420300 and PF3D7_1239200] ( Table 1 ), similar to results reported both by Hillier et al and with Toxoplasma Tg MORC complex (Farhat et al 2020, Antunes et al 2023, Srivastava et al 2023). Pf AP2-G5 (PF3D7_1139300) and Pf AP2-O5 (PF3D7_1449500) were enriched 20.5- and 14.99-fold, respectively, suggesting that these factors are likely major components in-complex with Pf MORC.…”

“…Pf MORC association with chromatin remodelers has been shown (Bryant et al 2020), but how Pf MORC regulates gene expression in the asexual stage has not been evaluated. In T. gondii , the Tg MORC: Tg ApiAP2 complex acts as a transcriptional repressor of sexual commitment (Farhat et al 2020, Antunes et al 2023, Srivastava et al 2023). This study found that Pf MORC co-immunoprecipitates with several chromatin remodeling proteins and many ApiAP2 transcription factors.…”

“…Despite the known DNA-binding sites of many ApiAP2 proteins (Flueck et al 2010, Santos et al 2017, Sierra-Miranda et al 2017, Josling et al 2020, Carrington et al 2021, Shang et al 2021, Singh et al 2021, Russell et al 2022, Shang et al 2022, Bonnell et al 2023), limited information is available for other accessory proteins. Recently, Tg MORC was identified in a complex with HDAC1, AP2XII-2, and AP2XII-1:AP2XI-2 in T. gondii and orchestrates epigenetic rewiring of sexual gene transcription (Farhat et al 2020, Antunes et al 2023, Srivastava et al 2023). In P. falciparum , Pf MORC has been copurified with several ApiAP2 proteins, as shown by different independent studies (Hillier et al 2019, Bryant et al 2020, Singh et al 2021).…”

“…Despite increasing evidence detailing ApiAP2 protein regulatory complexes (Santos et al 2017, Harris et al 2019, Hillier et al 2019, Hoeijmakers et al 2019, Farhat et al 2020, Josling et al 2020, Miao et al 2021, Antunes et al 2023, Srivastava et al 2023, Yuda et al 2023), the functional properties and specific interaction partners of many ApiAP2 TFs remain to be elucidated. A quantitative mass spectrometry-based analysis of the parasite protein interaction network has revealed links between ApiAP2 TFs and many chromatin remodelers, such as an extended Egl-27 and MTA1 homology 2 (EELM2) domain-containing proteins (PF3D7_0519800 and PF3D7_1141800), histone deacetylase protein 1 (HDAC1; PF3D7_0925700), and the microrchidia family protein Pf MORC (PF3D7_1468100) (Hillier et al 2019).…”

“…In the related apicomplexan parasite Toxoplasma gondii , Tg MORC functions as a repressor of sex-associated genes by recruiting the histone deacetylase protein Tg HDAC3 and forming heterogenous complexes with eleven ApiAP2 TFs (Farhat et al 2020). To date, only two Tg MORC:HDAC3 complexes have been characterized, including a Tg AP2XII-2:HDAC3 complex and a heterotrimeric Tg AP2XII-1:AP2XI-2:HDAC3 complex (Antunes et al 2023, Srivastava et al 2023).…”