Project description:The proposed use of Foxp3+ T-regulatory (Treg) cells as potential cellular therapy in patients with autoimmune diseases, or post-hemopoietic stem cell or organ transplantation, requires a sound understanding of the transcriptional regulation of Foxp3 expression. Conserved CpG dinucleotides in the Treg-specific demethylated region (TSDR) upstream of Foxp3 are demethylated only in stable, thymic-derived Foxp3+ Tregs. Since methyl-binding domain (Mbd) proteins recruit histone-modifying and chromatin-remodeling complexes to methylated sites, we tested whether targeting of Mbd2 might promote demethylation of Foxp3 and thereby promote Treg numbers or function. Surprisingly, while ChIP analysis showed Mbd2 binding to the Foxp3-associated TSDR site in Tregs, Mbd2 targeting by homologous recombination or siRNA decreased Treg numbers and impaired Treg suppressive function in vitro and in vivo. Moreover, we found complete TSDR demethylation in WT Tregs but >75% methylation in Mbd2-/- Tregs, whereas re-introduction of Mbd2 into Mbd2-null Tregs restored TSDR demethylation, Foxp3 gene expression and Treg suppressive function. Lastly, Mbd2-/- Tregs had markedly binding of the DNA demethylase enzyme, Tet2, in the TSDR region. These data show that Mbd2 has a key role in promoting TSDR demethylation, Foxp3 expression and Treg suppressive function. RNA from three independent samples from magnetically separated CD4+CD25+ Treg of MBD2–/– mice, compared to wild type control (all Balb/c background).
Project description:The proposed use of Foxp3+ T-regulatory (Treg) cells as potential cellular therapy in patients with autoimmune diseases, or post-hemopoietic stem cell or organ transplantation, requires a sound understanding of the transcriptional regulation of Foxp3 expression. Conserved CpG dinucleotides in the Treg-specific demethylated region (TSDR) upstream of Foxp3 are demethylated only in stable, thymic-derived Foxp3+ Tregs. Since methyl-binding domain (Mbd) proteins recruit histone-modifying and chromatin-remodeling complexes to methylated sites, we tested whether targeting of Mbd2 might promote demethylation of Foxp3 and thereby promote Treg numbers or function. Surprisingly, while ChIP analysis showed Mbd2 binding to the Foxp3-associated TSDR site in Tregs, Mbd2 targeting by homologous recombination or siRNA decreased Treg numbers and impaired Treg suppressive function in vitro and in vivo. Moreover, we found complete TSDR demethylation in WT Tregs but >75% methylation in Mbd2-/- Tregs, whereas re-introduction of Mbd2 into Mbd2-null Tregs restored TSDR demethylation, Foxp3 gene expression and Treg suppressive function. Lastly, Mbd2-/- Tregs had markedly binding of the DNA demethylase enzyme, Tet2, in the TSDR region. These data show that Mbd2 has a key role in promoting TSDR demethylation, Foxp3 expression and Treg suppressive function.
Project description:PGCs undergo two distinct stages of demethylation before reaching a hypomethylated ground state at E13.5. Stage 1 occurs between E7.25- E9.5 in which PGCs experience a global loss of cytosine methylation. However, discreet loci escape this global loss of methylation and between E10.5-E13.5, stage 2 of demethylation takes place. In this stage these loci are targeted by Tet1 and Tet2 leading to the loss of the remaining methylation and resulting in the epigenetic ground state. Our data shows that Dnmt1 is responsible for maintaining the methylation of loci that escape stage 1 demethylation, and that it functions in a UHRF1 independent manner. Our data further demonstrates that when these loci lose methylation prior to stage 2 it results in early activation of the meiotic program, which leads to precocious differentiation of the germ line resulting in a decreased pool of PGCs in the embryo and subsequent infertility in adult mice.