The methylcytosine oxidase TET proteins play important roles in DNA demethylation and development. In developing embryos, TET2 are upregulated during pre-implantation development, and significantly expressed in the trophectoderm and inner cell mass. In this study, we identified Barx2 as a new target of Tet2. Tet2 bound and demethylated the promoter of Barx2 in mouse embryonic stem cells (mESCs) to maintain the expression of Barx2. During mESC differentiation, Tet2 bound the promoter of Barx2 in day 4 embryonic bodies but not in day 8 EBs. However, Barx2 expression remained unchanged. Thus, Tet2 functioned as a demethylase and maintained the expression of Barx2 in undifferentiated and early differentiated mESCs. (C) 2020 Elsevier Inc. All rights reserved.