MBD2 regulates TH17 differentiation and experimental autoimmune encephalomyelitis by controlling the homeostasis of T-bet/Hlx axis

• Loss of Mbd2 completely protects mice from experimental autoimmune encephalomyelitis.
• Mbd2−/− mice reconstituted with wild-type splenocyte regain susceptibility to EAE.
• TH17 has a distinct methylation pattern T-bet/Hlx promoters compared to TH1/TH2/TH0.
• MBD2 interprets methylation in T-bet/Hlx promoter and regulates T cell polarization.

Unlike genetic alterations, epigenetic modifications are reversible and amenable to pharmacological interventions, which make them appealing targets for clinical therapy. However, little is known about epigenetic regulation in experimental autoimmune encephalomyelitis (EAE). Here we demonstrated that methyl-CpG-binding domain protein 2 (MBD2), an epigenetic regulator, controls autoimmunity and EAE through T-bet/Hlx. Tbx21 and Hlx underwent a DNA methylation turnover upon polarizations and a unique methylation pattern was essential for TH17 development. Loss of Mbd2 resulted in a defect for reading the information encoded by this methylation turnover, which disrupted the homeostasis of T-bet/Hlx axis and suppressed TH17 differentiation. DNA demethylation induced similar effect on helper T cell differentiation. Therefore, Mbd2−/− mice were completely protected from EAE. Pathogenic splenocytes isolated from wild-type mice challenged with MOG35-55 could adoptively transfer disease to Mbd2−/− mice. In addition, Mbd2−/− mice reconstituted with unstimulated wild-type splenocytes developed EAE as wild-type mice did. These data would provide novel insights into epigenetic regulation of EAE.