Project description:Dysregulation of imprinted gene loci also referred to as loss of imprinting (LOI) can result in severe developmental defects and other diseases, but the molecular mechanisms that ensure imprint stability remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) and the mechanism by which they ensure imprinting maintenance. Using pluripotent stem cells carrying an allele-specific reporter system, we demonstrate that the IG-DMR consists of two antagonistic regulatory elements: a paternally methylated CpG-island that prevents the activity of Tet dioxygenases and a maternally unmethylated regulatory element, which serves as a non-canonical enhancer and maintains expression of the maternal Gtl2 lncRNA by precluding de novo DNA methyltransferase function. Targeted genetic or epigenetic editing of these elements leads to LOI with either bi-paternal or bi-maternal expression patterns and respective allelic changes in DNA methylation and 3D chromatin topology of the entire Dlk1-Dio3 locus. Although the targeted repression of either IG-DMR or Gtl2 promoter is sufficient to cause LOI, the stability of LOI phenotype depends on the IG-DMR status, suggesting a functional hierarchy. These findings establish the IG-DMR as a novel type of bipartite control element and provide mechanistic insights into the control of Dlk1-Dio3 imprinting by allele-specific restriction of the active DNA (de)methylation machinery.
Project description:Imprinting at the Dlk1-Dio3 cluster is controlled by the IG-DMR, an imprinting control region differentially methylated between maternal and paternal chromosomes. The maternal IG-DMR is essential for imprinting control, functioning as a cis enhancer element. Meanwhile, DNA methylation at the paternal IG-DMR is thought to prevent enhancer activity. To explore whether suppression of enhancer activity at the methylated IG-DMR requires the transcriptional repressor TRIM28, we analyzed Trim28chatwo embryos and performed epistatic experiments with IG-DMR deletion mutants. We found that while TRIM28 regulates the enhancer properties of the paternal IG-DMR, it also controls imprinting through other mechanisms. Additionally, we found that the paternal IG-DMR, previously deemed dispensable for imprinting, is required in certain tissues, demonstrating that imprinting is regulated in a tissue-specific manner. Using ChRO-seq to analyze nascent transcription, we show that different tissues have a distinctive regulatory landscape at the Dlk1-Dio3 cluster, providing insight into potential mechanisms of tissue-specific imprinting control. ChRO-seq identified 30 novel transcribed regulatory elements, including a candidate regulatory region that depends on the paternal IG-DMR. Together, our findings challenge the model that Dlk1-Dio3 imprinting is regulated through a single mechanism and demonstrate that different tissues use distinct strategies for imprinting control.
Project description:This SuperSeries is composed of the SubSeries listed below. Abstract Among all mammalian cell types, sperm cells exhibit one of the highest levels of DNA methylation, with ~80% of CpG sites being methylated. The role of this sperm hypermethylation in offspring development, aside from the methylation at the well-characterized H19-DMR and Dlk1-Dio3 intergenic germline DMR (IG-DMR) loci, remains largely unexplored. In mouse germ cells, removal of DNA methylation by deleting methyltransferase (Dnmt) genes causes meiotic catastrophe and infertility. To circumvent this limitation, we inactivated them instead in androgenetic haploid embryonic stem cells (AG-haESCs) lacking H19-DMR and IG-DMR to remove methylation prior to oocyte injection, and subsequently reactivated them in the resulting embryos during cleavage, to ensure Dnmt sufficiency. This strategy enabled the generation of viable offspring from unmethylated paternally-derived haploid cells. In the resulting embryos, the paternal genome rapidly reacquired methylation and was comparable to wild-type in post-implantation embryos. These semi-cloned embryos could develop to term and survived to adulthood, exhibiting near-normal morphological and physiological parameters. These findings indicate that the essential hereditary function of the paternal genome methylation is mainly restricted to the imprinted loci Igf2-H19 and Dlk1-Dio3, while methylation elsewhere appears dispensable for subsequent development, as de novo methylation activity intrinsic to the early embryo ensures epigenetic reprogramming for offspring development.
Project description:We report the DNA-methylation profiling of 10 regions selected from the DLK1-DIO3 domain on chromosome 14q32 in BM/PB samples from patients with acute promyelocytic leukaemia (APL), other subclasses of acute myeloid leukaemia and healthy donors, using high-throughput amplicon bisulfite sequencing with Roche 454 technology. We identify monoallelic-hypermethylation in APL only at the differentially methylated region (DMR) located upstream from the MEG3 gene (MEG3-DMR), whereas no changes in the DNA methylation profile were detected at the imprinting control region of the domain (IG-DMR) among the samples analysed. We show that the expression profile of 6 miRNAs clustered downstream from the MEG3-DMR correlates with the methylation profile at both DMRs. We demonstrate that miRNAs expression negatively correlates with DNA-methylation at the IG-DMR and MEG3 gene-body, whereas the correlation was positive for the CpGs located in the promoter of MEG3, including the binding sites for the insulator CTCF. We propose a loss of imprinting at the CTCF binding sites in patients with APL. These results are consistent with the previously reported DLK1-DIO3 miRNAs overexpression in APL, indicating a possible involvement of these ncRNAs in the pathogenesis of the disease. Investigation of the epigenetic regulation of the miRNAs clustered in 14q32 by next-generation sequencing
Project description:Among all mammalian cell types, sperm exhibit the highest level of DNA methylation, with approximately 70–80% of CpG sites being methylated. The role of this paternal hypermethylation in embryonic developmental competence, aside from the well-characterized H19-DMR and Dlk1-Dio3 intergenic germline DMR (IG-DMR) loci, remains largely unexplored. In mouse male germ cells, the lack of DNA methyltransferase (Dnmt) causes a loss of methylation, leading to meiotic catastrophe and infertility. To circumvent this limitation, we used sperm-like androgenetic haploid embryonic stem cells (AG-haESCs) for oocyte injection to produce offspring. Using CRISPR/Cas9, we effectively inactivated Dnmt1, Dnmt3a and Dnmt3b in AG-haESCs and later reactivated them in the resulting embryos, overcoming Dnmt haploinsufficiency and enabling the generation of viable offspring from methylation-deficient haploid cells. In the offspring embryos, the paternal genome derived from Dnmt-inactivated AG-haESCs rapidly reacquired methylation and restored a methylome in post-implantation embryos comparable to that of wild-type AG-haESC counterparts. These semi-cloned embryos could develop to term and survived to adulthood, exhibiting near-normal morphological and physiological parameters. These findings indicate that the functional significance of paternal genome methylation is mainly restricted to the imprinted loci Igf2-H19 and Dlk1-Dio3, while methylation of the paternal genome elsewhere appears dispensable for normal development.
Project description:Among all mammalian cell types, sperm exhibit the highest level of DNA methylation, with approximately 70–80% of CpG sites being methylated. The role of this paternal hypermethylation in embryonic developmental competence, aside from the well-characterized H19-DMR and Dlk1-Dio3 intergenic germline DMR (IG-DMR) loci, remains largely unexplored. In mouse male germ cells, the lack of DNA methyltransferase (Dnmt) causes a loss of methylation, leading to meiotic catastrophe and infertility. To circumvent this limitation, we used sperm-like androgenetic haploid embryonic stem cells (AG-haESCs) for oocyte injection to produce offspring. Using CRISPR/Cas9, we effectively inactivated Dnmt1, Dnmt3a and Dnmt3b in AG-haESCs and later reactivated them in the resulting embryos, overcoming Dnmt haploinsufficiency and enabling the generation of viable offspring from methylation-deficient haploid cells. In the offspring embryos, the paternal genome derived from Dnmt-inactivated AG-haESCs rapidly reacquired methylation and restored a methylome in post-implantation embryos comparable to that of wild-type AG-haESC counterparts. These semi-cloned embryos could develop to term and survived to adulthood, exhibiting near-normal morphological and physiological parameters. These findings indicate that the functional significance of paternal genome methylation is mainly restricted to the imprinted loci Igf2-H19 and Dlk1-Dio3, while methylation of the paternal genome elsewhere appears dispensable for normal development.
Project description:Among all mammalian cell types, sperm exhibit the highest level of DNA methylation, with approximately 70–80% of CpG sites being methylated. The role of this paternal hypermethylation in embryonic developmental competence, aside from the well-characterized H19-DMR and Dlk1-Dio3 intergenic germline DMR (IG-DMR) loci, remains largely unexplored. In mouse male germ cells, the lack of DNA methyltransferase (Dnmt) causes a loss of methylation, leading to meiotic catastrophe and infertility. To circumvent this limitation, we used sperm-like androgenetic haploid embryonic stem cells (AG-haESCs) for oocyte injection to produce offspring. Using CRISPR/Cas9, we effectively inactivated Dnmt1, Dnmt3a and Dnmt3b in AG-haESCs and later reactivated them in the resulting embryos, overcoming Dnmt haploinsufficiency and enabling the generation of viable offspring from methylation-deficient haploid cells. In the offspring embryos, the paternal genome derived from Dnmt-inactivated AG-haESCs rapidly reacquired methylation and restored a methylome in post-implantation embryos comparable to that of wild-type AG-haESC counterparts. These semi-cloned embryos could develop to term and survived to adulthood, exhibiting near-normal morphological and physiological parameters. These findings indicate that the functional significance of paternal genome methylation is mainly restricted to the imprinted loci Igf2-H19 and Dlk1-Dio3, while methylation of the paternal genome elsewhere appears dispensable for normal development.
Project description:We report the DNA-methylation profiling of 10 regions selected from the DLK1-DIO3 domain on chromosome 14q32 in BM/PB samples from patients with acute promyelocytic leukaemia (APL), other subclasses of acute myeloid leukaemia and healthy donors, using high-throughput amplicon bisulfite sequencing with Roche 454 technology. We identify monoallelic-hypermethylation in APL only at the differentially methylated region (DMR) located upstream from the MEG3 gene (MEG3-DMR), whereas no changes in the DNA methylation profile were detected at the imprinting control region of the domain (IG-DMR) among the samples analysed. We show that the expression profile of 6 miRNAs clustered downstream from the MEG3-DMR correlates with the methylation profile at both DMRs. We demonstrate that miRNAs expression negatively correlates with DNA-methylation at the IG-DMR and MEG3 gene-body, whereas the correlation was positive for the CpGs located in the promoter of MEG3, including the binding sites for the insulator CTCF. We propose a loss of imprinting at the CTCF binding sites in patients with APL. These results are consistent with the previously reported DLK1-DIO3 miRNAs overexpression in APL, indicating a possible involvement of these ncRNAs in the pathogenesis of the disease.
Project description:The mammalian imprinted Dlk1-Dio3 domain contains multiple lncRNAs, mRNAs, the largest miRNA cluster in the genome and four differentially methylated regions (DMRs), and deletion of maternal RNA within this locus results in embryonic lethality, but the mechanism by which this occurs is not clear. Here, we optimized the model of maternally expressed RNAs transcription termination in the domain and found that the cause of embryonic death was apoptosis in the embryo, particularly in the liver. We generated a mouse model of maternally expressed RNAs silencing in the Dlk1-Dio3 domain by inserting a 3×polyA termination sequence in Gtl2 locus. By analyzing mouse embryos RNA-Seq data combined with histological analysis, we found that silence of maternally expressed RNAs in the domain activated apoptosis, causing vascular rupture of fetal liver, resulting hemorrhage and injury. Mechanistically, termination of Gtl2 transcription results in the silencing of the maternally expressed RNAs and activation of the paternally expressed genes in the interval, and it is the gene itself rather than the IG-DMR and Gtl2-DMR that causes the above phenotypes. In conclusion, these findings illuminate a novel mechanism by which silencing of the maternally expressed RNAs within Dlk1-Dio3 domain leads to hepatic hemorrhage and embryonic death through activation of the apoptosis.
Project description:Our previous study demonstrated a significant upregulation of a large set of miRNAs at the genomic imprinted Dlk1-Dio3 locus in lymphocytes of diverse murine lupus-prone strains. The upregulation of Dlk1-Dio3 miRNAs in lupus-prone mice is correlated with the global DNA hypomethylation. In this study, by performing genome-wide DNA methylation analysis, we reported that Dlk1-Dio3 genomic region in CD4+ T cells of MRL/lpr mice was hypomethylated, further linking hypomethylation to the increased expression of Dlk1-Dio3 miRNAs in lupus. Then, we assessed the gene expression levels of enzymes that either write (DNA methyltransferases, DNMTs) or erase DNA methylation (Ten-eleven translation proteins, TETs) to understand the molecular contributor to the DNA hypomethylation in MRL/lpr CD4+ T cells. The expression levels of Dnmt1, Dnmt3b, Tet1, and Tet2 were significantly increased in CD4+ T cells of MRL/lpr mice, as well as in B6/lpr and B6.sle123 mice, compared to their respective control mice. These data indicate the significant involvement of the TETs-mediated active demethylation pathway rather than reduced DNMTs-mediated passive demethylation pathway in the hypomethylation of murine lupus CD4+ T cells. The transcription factor, early growth response 2 (EGR2) is critically involved in regulating T cell functions and autoimmunity. In this research, we found that Egr2 deletion in B6/lpr mice notably reduced methylation-sensitive Dlk1-Dio3 cluster miRNAs expression in CD4+ T cells. Surprisingly, even though EGR2 has been shown to induce DNA demethylation by recruiting TET2, we found that deleting Egr2 in B6/lpr mice induced a higher number of hypomethylated DMRs than hypermethylated DMRs at either whole genome or the Dlk1-Dio3 locus in CD4+ T cells of B6/lpr mice. These data are the first finding on the positive role of EGR2 on the expression of Dlk1-Dio3 cluster miRNAs in lupus mice. Given that Dlk1-Dio3 miRNAs target the major signaling pathways in autoimmunity, these data provide a new perspective in understanding the potential pathogenic role of upregulated EGR2 in lupus.