Link between the EZH2 noncanonical pathway and microtubule organization center polarization during early T lymphopoiesis

EZH2 plays an essential role at the β-selection checkpoint of T lymphopoiesis by regulating histone H3 lysine 27 trimethylation (H3K27me3) via its canonical mode of action. Increasing data suggest that EZH2 could also regulate other cellular functions, such as cytoskeletal reorganization, via its noncanonical pathway. Consequently, we investigated whether the EZH2 noncanonical pathway could be involved in early T-cell maturation, which requires cell polarization. We observed that EZH2 localization is tightly regulated during the early stages of T-cell development and that EZH2 relocalizes in the nucleus of double-negative thymocytes enduring TCRβ recombination and β-selection processes. Furthermore, we observed that EZH2 and EED, but not Suz12, colocalize with the microtubule organization center (MTOC), which might prevent its inappropriate polarization in double negative cells. In accordance with these results, we evidenced the existence of direct or indirect interaction between EED and α-tubulin. Taken together, these results suggest that the EZH2 noncanonical pathway, in association with EED, is involved in the early stages of T-cell maturation.