Project description:Here, we first establish an easy Multi-Stop system to simultaneously inactivate genes involved in DNA methylation and demethylation in zygotes through introduction of the stop codon by hA3A-eBE-Y130F-mediated base editor (BE). While Multi-Stop-derived Dnmt-null embryos display embryonic lethal due to gastrulation failure. Moreover, mutation combinations between Tet and Dnmt families show severe embryonic lethal and Dnmt1 or Dnmt3a/3b is indispensable for mouse gastrulation. Then WGBS and RNA-seq analysis of different mutant embryos reveals genes jointly maintained by Dnmt1 and Dnmt3a/3b that are critical for gastrulation.
Project description:Here, we establish a system to simultaneously inactivate Dnmts in one step through screening for base editors that can efficiently introduce a stop codon endogenously. Dnmt-null embryos display primitive streak elongation failure at E7.5. Interestingly, although DNA methylation is absent, gastrulation-related pathways are down-regulated in Dnmt-null embryos. Moreover, DNMT1 or DNMT3A/3B are indispensable for gastrulation and their functions are independent of TET proteins. Hypermethylation can be sustained by either DNMT1 or DNMT3A/3B at some promoters, which are mainly related to miRNAs. Strikingly, majority of hypermethylated promoter-related miRNAs are overexpressed and located at the Dlk1-Dio3 imprinted region. The predicted targets of these miRNAs tend to be down-regulated and enriched in the gastrulation-related pathways in Dnmt-null embryos. Finally, introduction of a single mutant allele of six miRNAs partially restores primitive streak elongation in Dnmt-null embryos.
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 DNMT3A/3B DKO human ES cells
Project description:Nephron number is a major determinant of long-term renal function. We hypothesized a link between epigenetic regulation and nephron formation. In support of this hypothesis, expression analysis evidenced high levels of DNA methyltransferases Dnmt1 and Dnmt3a in the nephrogenic zone of the developing mouse kidney. Using targeted loss-of-function manipulations in mice, we show that deletion of Dnmt1 in nephron progenitor cells results in a marked hypoplasia and reduction of nephron number at birth. In contrast, deletion of Dnmt3a/3b in nephron progenitor cells or deletion of Dnmt1/3a/3b in differentiated renal cells did not lead to any overt kidney phenotype. Whole mount optical projection tomography and 3D-reconstructions uncovered a significant reduction of stem cell niches and progenitor cells in Dnmt1-deficient mice. Ultimately, RNA sequencing analysis revealed that Dnmt1 controls DNA transcription regulating progenitor renewal, identity and differentiation. In summary, this study establishes DNA methylation as key regulatory event of prenatal renal programming.
Project description:We generated base-resolution DNA methylomes of a series of DNMT knockout (KO) ES cells with improved coverage at highly repetitive elements. We find that DNMT1- and DNMT3a/3b-dependent activities actually work complementarily and simultaneously to establish symmetric CG methylation and CHH (H=A, T or C) methylation, and unexpectedly have “division of labor” to suppress retrotransposon long terminal repeats (LTRs) and long interspersed elements (LINEs), respectively. Our data also reveal CG density number of 30 seems like a 'threshold' to predetermine the level of methylation in wild type cells and the magnitude of methylation reduction in KO cells. Only genes with low CG number are either induced or surprisingly suppressed in hypomethylated genome. Our data unveil the concerted action of DNMT enzymes in the establishment/maintenance of methylation patterns. Genomic DNA from four different cell lines were treated with bisulfite and sequenced with the Illumina HiSeq platform using paired end reads.
Project description:Base editor is also a powerful tool to introduce early stop codons to simultaneously silence multiple genes to study family gene function in embryo development. Here, we identified the highest efficiency base editing system (hA3A-eBE-Y130F) with few sgRNA independent off-target sites among six well-established base editors in mouse embryo. Further, we developed a Multi-Stop system to simultaneously knock-out all Ten-eleven translocation (TET) family of dioxygenase genes (Tet1, Tet2 and Tet3) in zygotic genome leads embryo die before 10.5 days of gestation. Moreover, we showed that inactivation of three DNA methyltransferases genes (Dnmt1, Dnmt3a and Dnmt3b) in zygote leads to gastrulation failure. We also obtained multiple TET and DNMT family genes (6KO: Dnmt1/3a/3b and Tet1/2/3; 5KO: Dnmt3a/3b and Tet1/2/3; 4KO: Dnmt1 and Tet1/2/3) deactivated mouse embryos in one step, which indicated that Dnmt1 or Dnmt3a/b is indispensable for mouse gastrulation.
Project description:We generated base-resolution DNA methylomes of a series of DNMT knockout (KO) ES cells with improved coverage at highly repetitive elements. We find that DNMT1- and DNMT3a/3b-dependent activities actually work complementarily and simultaneously to establish symmetric CG methylation and CHH (H=A, T or C) methylation, and unexpectedly have “division of labor” to suppress retrotransposon long terminal repeats (LTRs) and long interspersed elements (LINEs), respectively. Our data also reveal CG density number of 30 seems like a 'threshold' to predetermine the level of methylation in wild type cells and the magnitude of methylation reduction in KO cells. Only genes with low CG number are either induced or surprisingly suppressed in hypomethylated genome. Our data unveil the concerted action of DNMT enzymes in the establishment/maintenance of methylation patterns.
Project description:DNA methylation is an epigenetic modification associated with transcriptional repression of promoters and is essential for mammalian development. Establishment of DNA methylation is mediated by the de novo DNA methyltransferases DNMT3A and DNMT3B, whereas DNMT1 ensures maintenance of methylation through replication. Absence of these enzymes is lethal, and somatic mutations in these genes have been associated with several human diseases. How genomic DNA methylation patterns are regulated remains poorly understood, as the mechanisms that guide recruitment and activity of DNMTs in vivo are largely unknown. To gain insights into this matter we determined chromosomal binding and site-specific activity of the mammalian de novo DNA methyltransferases DNMT3A and DNMT3B. We show that both enzymes localize to methylated, CpG dense regions in mouse stem cells, yet are excluded from active promoters and enhancers. By specifically measuring sites of de novo methylation, we observe that enzymatic activity reflects chromosomal binding. De novo methylation increases with CpG density, yet is excluded from nucleosomes. Notably, we observed selective binding of DNMT3B to the bodies of transcribed genes, which leads to their preferential methylation. This targeting to transcribed sequences requires SETD2-mediated methylation of lysine 36 on histone H3 and a functional PWWP domain of DNMT3B. Together these findings reveal how sequence and chromatin cues guide de novo methyltransferase activity to ensure methylome integrity. Whole-genome bisulfite sequencing for Dnmt1,3a,3b-triple-KO ES cells expressing DNMT3A2 or DNMT3B1 and for Dnmt1,3a,3b,Setd2-KO ES cells expressing DNMT3B1