Toxoplasma gondii infection leads to epigenetic reprogramming in mouse neuroblasts cells

Toxoplasmosis is a highly prevalent disease caused by the protozoan Toxoplasma gondii. Vertical transmission during pregnancy can lead to severe malformations and our group has demonstrated that infection of neural progenitor cells impairs neurogenesis. The neurogenic program is coordinated by epigenetic marks that dictate cell fate. Interestingly, T. gondii secretes effector proteins that reprogram the host cell’s epigenetic machinery  to modulate the innate inflammatory response. Specifically, some proteins, including TEEGR (Toxoplasma E2F4-associated EZH2-inducing gene regulator), are capable of modulating the profile of Histone 3 (H3) methylation and promote parasite persistence. In this work, we investigated the effect of T. gondii infection on histone H3 methylation in murine neuroblasts, specifically tri-methylation of lysines 4 (K4) and 27 (K27), responsible for chromatin accessibility or repression, respectively. Neuro2a cells were infected with three different T. gondii strains, representative of the main genotypes: type I (RH), type II (ME49) and type III (VEG). After 24 and 96 hours of infection (hpi), the levels of H3K4me3 and H3K27me3 were assessed by western blotting. Moreover, we analyzed the expression of Ezh1 and Ezh2, responsible for the triple methylation of H3K27. Our results demonstrated that at 24hpi, the RH and VEG strains promoted an increase in H3K4me3 levels (RH: 1,40 ± 0,11 fold-change, VEG: 1,39 ± 0,27 fold-change), whereas the ME49 strain increased the levels of H3K27me3 (ME: 1,87 ± 0,48 fold-change). The expressions of Ezh1 and Ezh2 were not altered by infection. Taken together, these results show that each strain promotes a different profile of epigenetic reprogramming, reinforcing that different T. gondii effector proteins play a major role in neurodevelopmental abnormalities.