Project description:White adipose tissue (WAT) is a key regulator of systemic energy metabolism, and impaired WAT plasticity characterized by enlargement of preexisting adipocytes associates with WAT dysfunction, obesity and metabolic complications. However, the mechanisms that retain proper adipose tissue plasticity required for metabolic fitness are unclear. Here, we comprehensively showed that adipocyte-specific DNA methylation, manifested in enhancers and CTCF sites, directs distal enhancer-mediated transcriptomic features required to conserve metabolic functions of white adipocytes. Particularly, genetic ablation of adipocyte Dnmt1, the major methylation writer, led to increased adiposity characterized by increased adipocyte hypertrophy along with reduced expansion of adipocyte precursors (APs). These effects of Dnmt1 deficiency provoked systemic hyperlipidemia and impaired energy metabolism both in lean and obese mice. Mechanistically, Dnmt1 deficiency abrogated mitochondrial bioenergetics by inhibiting mitochondrial fission and promoted aberrant lipid metabolism in adipocytes, rendering adipocyte hypertrophy and WAT dysfunction. Dnmt1-dependent DNA methylation prevented aberrant CTCF binding and, in turn, sustained the proper chromosome architecture to permit interactions between enhancer and dynamin-related protein gene Drp1 in adipocytes. Also, adipose DNMT1 expression inversely correlated with adiposity and markers of metabolic health, but positively correlated with AP-specific markers in obese human subjects. Thus, these findings support strategies utilizing Dnmt1 action on mitochondrial bioenergetics in adipocytes to combat obesity and related metabolic pathology.
Project description:Ovarian cancer (OC) cells frequently metastasize to the omentum and adipocytes play a significant role in ovarian tumor progression. Therapeutic interventions targeting aberrant DNA methylation in ovarian tumors have shown promise in the clinic but the effects of epigenetic therapy on the tumor microenvironment are understudied. Here, we examined the effect of adipocytes on OC cell behavior in culture and impact of targeting DNA methylation in adipocytes on OC metastasis. The presence of adipocytes increased OC cell migration and invasion and proximal and direct co-culture of adipocytes .increased OC proliferation alone or after treatment with carboplatin. Treatment of adipocytes with hypomethylating agent guadecitabine decreased migration and invasion of OC cells towards adipocytes. Due to this result, we performed RNA-seq of adipocytes treated with DNMT1 inhibitor to analyze differential gene expression changes that occur in the adipocyte that may explain the above observation that hypomethylating agent treatment of adipocytes decrease migration and invasion.
Project description:The epigenome, including DNA methylation, is stably propagated during mitotic division. However, single-cell clonal expansion produces heterogeneous methylomes, raising the question of how the DNA methylome remains stable despite constant epigenetic drift. Here, we report that a clonal population of DNA (cytosine-5)-methyltransferase 1 (DNMT1)-only cells produces a heterogeneous methylome, which is robustly propagated on cell expansion and differentiation. Our data show that DNMT1 has imprecise maintenance activity and likely possesses weak de novo activity, leading to spontaneous ‘epimutations’. However, these epimutations tend to be corrected through a neighbor-guided mechanism, ikely enabled by environment-sensitive de novo activity (‘tuner’) and maintenance activity (‘stabilizer’) of DNMT1. By generating base-resolution maps of de novo and maintenance activities, we find that H3K9me2/3-marked regions show enhanced de novo activity, and CpG islands have both poor maintenance and de novo activities. The imprecise epigenetic machinery coupled with neighbor-guided correction may be a fundamental mechanism underlying robust yet flexible epigenetic inheritance.
Project description:DNA methylation is a key epigenetic modification involved in regulating gene expression and maintaining genomic integrity. Somatic patterns of DNA methylation are largely static, apart from focal dynamics at gene regulatory elements. To further advance our understanding of the role of DNA methylation in human development and disease, we inactivated all three catalytically active DNA methyltransferases in human embryonic stem cells (ESCs) using CRISPR/Cas9 genome editing. Disruption of DNMT3A or DNMT3B individually, as well as of both enzymes in tandem, creates viable, pluripotent cell lines with distinct effects on their DNA methylation landscape as assessed by whole-genome bisulfite sequencing. Surprisingly, in contrast to mouse, deletion of DNMT1 resulted in rapid cell death in human ESCs. To overcome the immediate lethality, we generated a doxycycline (DOX) responsive tTA-DNMT1* rescue line and readily obtained homozygous DNMT1 mutant lines. However, DOX-mediated repression of the exogenous DNMT1* initiates rapid, global loss of DNA methylation, followed by extensive cell death, demonstrating that DNA methylation is essential for human ESCs cultured in standard conditions. In summary, our data provide a comprehensive characterization of DNMT mutant ESCs, including single base genome-wide maps of their targets. RRBS methylation profiling of a time course of DNMT1* withdrawal in human ES cells
Project description:Stable inheritance of DNA methylation is critical for maintaining the differentiated phenotypes in multicellular organisms. However, the molecular basis ensuring high fidelity of maintenance DNA methylation is largely unknown. Here, we demonstrate that two distinct modes of DNMT1 recruitment, one is DNA replication-coupled and the other is uncoupled mechanism, regulate the stable inheritance of DNA methylation. PCNA-associated factor 15 (PAF15) represents a primary target of UHRF1 and undergoes dual mono-ubiquitylation (PAF15Ub2) on chromatin. PAF15Ub2 specifically interacts with DNMT1 and controls the recruitment of DNMT1 in a DNA replication-coupled manner. Thus, loss of PAF15Ub2 results in impaired DNA methylation at sites replicating during early S phase. In contrast, outside of S phase or when PAF15 ubiquitylation is perturbed, UHRF1 ubiquitylates histone H3 to promote DNMT1 recruitment. Together, we identify replication-coupled and uncoupled mechanisms of maintenance DNA methylation, both of which collaboratively ensure the stable DNA methylation.
Project description:Altered DNA methylation and associated destabilization of genome integrity and function is a hallmark of cancer. Replicative senescence imposes a limit on proliferative potential that all cancer cells must bypass. Compared to proliferating cells, senescent cells exhibit marked chromatin re-organization. Here we show by whole-genome single-nucleotide bisulfite sequencing that replicative senescent human cells exhibit widespread alterations in their DNA methylome. These changes are linked to mislocalization of the maintenance DNA methyltransferase (DNMT1) in cells approaching senescence, altered replication-coupled DNA methylation and de-repression of repetitive satellite sequences. Deficiency of DNMT1 triggers chromatin changes characteristic of senescence and expression of satellite sequences. Most importantly, but paradoxically, gains and losses of methylation in replicative senescence are similar to those in cancer, and this M-bM-^@M-^XreprogrammedM-bM-^@M-^Y methylation landscape is largely retained when cells escape or bypass senescence. In sum, altered regulation of DNMT1 in cells approaching replicative senescence contributes to changes in chromatin structure and function. Consequently, if senescent cells escape the proliferative barrier, they already harbor epigenetic changes likely to promote malignancy. Examination of methylation status in IMR90 cells
Project description:Dramatic change in DNA methylation patterns and levels both globally and/or locus-specifically is associated with the process of cell linage specification and somatic reprogramming. We found the expression of DNA methyltransferase 1 (Dnmt1) is tightly regulated by the features of cell cycle, which we referred as cell cycle-directed Dnmt1 expression adjustment. To further investigate how DNA methylation is affected by this mechanism, we applied reduced representation bisulphate sequencing (RRBS) to map genome-wide DNA methylation on mouse embryonic fibroblasts (MEFs). To characterize how this mechanism affects somatic reprogramming, samples of MEFs induced by Yamanaka factors (Sox2, Klf4, Oct4, cMyc) was included. The cell cycle was accelerated by shRNA targeted to p53, and the expression of Dnmt1 was manipulated genetically. We find 5mC level remains constant in regardless of cell proliferation rate, a result from the adjusted expression of Dnmt1. However, repressed expression of Dnmt1 in fast-proliferating cells results in global DNA demethylation. The patterns of DNA methylation and demethylation affected by this mechanism is sensitive to CpG densities. Generally, the results demonstrate cell cycle-directed Dnmt1 expression adjustment as an mechanism for the insurance of the stability of genomic 5mC inheritance.
Project description:DNA methylation is a key epigenetic modification involved in regulating gene expression and maintaining genomic integrity. Somatic patterns of DNA methylation are largely static, apart from focal dynamics at gene regulatory elements. To further advance our understanding of the role of DNA methylation in human development and disease, we inactivated all three catalytically active DNA methyltransferases in human embryonic stem cells (ESCs) using CRISPR/Cas9 genome editing. Disruption of DNMT3A or DNMT3B individually, as well as of both enzymes in tandem, creates viable, pluripotent cell lines with distinct effects on their DNA methylation landscape as assessed by whole-genome bisulfite sequencing. Surprisingly, in contrast to mouse, deletion of DNMT1 resulted in rapid cell death in human ESCs. To overcome the immediate lethality, we generated a doxycycline (DOX) responsive tTA-DNMT1* rescue line and readily obtained homozygous DNMT1 mutant lines. However, DOX-mediated repression of the exogenous DNMT1* initiates rapid, global loss of DNA methylation, followed by extensive cell death, demonstrating that DNA methylation is essential for human ESCs cultured in standard conditions. In summary, our data provide a comprehensive characterization of DNMT mutant ESCs, including single base genome-wide maps of their targets.