Project description:Global heterochromatin reduction, which is one of the hallmarks of aging cells, is associated with reduced transposable element repression and increased risk of chromatin instability. To ensure genomic integrity, the irreparable cells in a population exit permanently from the cell cycle, and this process is termed “senescence”. However, senescence only blocks the expansion of unwanted cells, and the aberrant chromatin of senescent cells remains unstable. Serendipitously, we found that the transient ectopic expression of a repressive epigenetic modulator, DNA methyltransferase 3-like (DNMT3L) was sufficient to delay the premature senescence progression of late-passage mouse embryonic fibroblasts (MEFs) associated with a tightened global chromatin structure. DNMT3L induces more repressive H3K9 methylation on endogenous retroviruses and downregulates the derepressed transposons in aging MEFs. In addition, we found that a pulse of ectopic DNMT3L resulted in the reestablishment of H3K27me3 on polycomb repressive complex 2 (PRC2)-target genes that were derepressed in old MEFs. We demonstrated that ectopic DNMT3L interacted with PRC2 in MEFs. Our data also suggested that ectopic DNMT3L might guide PRC2 to redress deregulated chromatin regions in aging cells. This study might lead to an epigenetic reinforcement strategy for overcoming aging-associated epimutation and senescence.
Project description:During reprogramming of mouse embryonic fibroblast, pluripotent genes are up-regulated. Once iPSCs are successfully reprogrammed, the global gene profiles of iPSCs are comparable to mouse ESC. We used microarrays to detail the global programme of gene expression in iPSCs, mESCs, MEFs.
Project description:The core purpose of this project is to identify the novel epigenetic factors which play a crucial role on regulating stem cells developed from embryo development to ageing through the longitudinal analysis of their transcriptome, protein interactome, and post- translational modification network. Thus, this study would not only advance our understanding of epigenetic nature of stem cells through whole life, but also provide the novel strategy to develop the next generation stem cell therapeutics. According to our previous reports, we found that DNA methylation, particularly mediated by Dnmt3L could play a common epigenetic signature for modulating the stemness potency of both embryonic and adult stem cells. To investigate the post-translational modifications of Dnmt3L protein, we performed mass spectrometry analysis of Flag-tagged Dnmt3L proteins in murine embryonic stem cells (ESCs) and then identified several acetylated lysine residues. To examine their functional roles, we manufactured the lentivirus containing wild type Dnmt3L or the acetylated lysine mutants and they established the ESC cell lines stably harboring these constructs. To focus on epigenetic mechanism for stem cell biology, we will narrow down the key acetylated lysine sites of Dnmt3L, which can characteristically regulate the epigenetic status or transcription gene ontology. To get mechanistic insights, the transcriptome and DNA methylome features of the established ESC cell lines will be analyzed. The functional significance was examined by a series of experiments for in vitro and in vivo self-renewal and differentiation assays. Finally, we would extend these results to develop the efficient ex vivo expansion protocol for adult stem cells, particularly focusing on human mesenchymal stem cells. We expect that this proposal will not only advance our understating the epigenetic landscape of stem cell population but also contribute to establish the clinically best-suitable stem cell population. In addition, this study can be appliable to get a novel conceptional advances in other biological research such as cancer biology and ageing research.
Project description:Global heterochromatin reduction, which is one of the hallmarks of senescent cells, is associated with reduced transposable element repression and increased risk of chromatin instability. To ensure genomic integrity, the irreparable cells in a population exit permanently from the cell cycle, and this process is termed "senescence." However, senescence only blocks the expansion of unwanted cells, and the aberrant chromatin of senescent cells remains unstable. Serendipitously, we found that the transient ectopic expression of a repressive epigenetic modulator, DNA methyltransferase 3-like (DNMT3L) was sufficient to delay the premature senescence progression of late-passage mouse embryonic fibroblasts (MEFs) associated with a tightened global chromatin structure. DNMT3L induces more repressive H3K9 methylation on endogenous retroviruses and downregulates the derepressed transposons in aging MEFs. In addition, we found that a pulse of ectopic DNMT3L resulted in the reestablishment of H3K27me3 on polycomb repressive complex 2 (PRC2)-target genes that were derepressed in old MEFs. We demonstrated that ectopic DNMT3L interacted with PRC2 in MEFs. Our data also suggested that ectopic DNMT3L might guide PRC2 to redress deregulated chromatin regions in cells undergoing senescence. This study might lead to an epigenetic reinforcement strategy for overcoming aging-associated epimutation and senescence.
Project description:We used RRBS to analyze DNA methylation in mESC lines deficient for maternal Dnmt3L (Dnmt3L mKO), zygotic Dnmt3L (Dnmt3L KO), and both maternal and zygotic Dnmt3L (Dnmt3L mzKO). Compared to wild-type (WT) mESCs, Dnmt3L mKO mESCs exhibit severe loss of methylation at imprinted loci but no changes in global DNA methylation, Dnmt3L KO mESCs exhibit moderate loss of methylation at many Dnmt3a target regions but do not affect methylation at imprinted loci, and Dnmt3L mzKO mESCs exhibit combined changes of mKO and KO cells, with severe loss of methylation at imprinted loci and moderate loss of methylation at Dnmt3a target regions.
Project description:We found that Dnmt3l-KO donor cells display decreased levels of H3K9me3 and H3K27me3 accumulation, higher level of active histone mark H3K27ac and increased cytoplasmic localization of HDAC1, implicating a permissive epigenetic state beneficial for nuclear reprogramming. To investigate the gene expression profiles of MEFs and to find out the potential genes responsible for the improvement of Dnmt3l-KO cloned embryos.