Project description:Epigenetic reprogramming including demethylation of DNA occurs in mammalian primordial germ cells (PGCs) and in early embryos, and is important for the erasure of imprints and epimutations, and the return to pluripotency. The extent of this reprogramming and its molecular mechanisms are poorly understood. We previously showed that the cytidine deaminases Aid and Apobec1 can deaminate 5-methylcytosine in vitro and in E coli, and in the mouse are expressed in tissues in which demethylation occurs. Here we profiled DNA methylation throughout the genome by unbiased bisulfite Next Generation Sequencing (BS-Seq) in wildtype and Aid deficient PGCs at E13.5. Wildtype PGCs revealed dramatic genome-wide erasure of methylation to a level below that of methylation deficient (Np95-/-) ES cells, with female PGCs being less methylated than male ones. By contrast, Aid deficient PGCs were up to three times more methylated than wildtype ones; this substantial difference occurred throughout the genome, with introns, intergenic regions and transposons being relatively more methylated than exons. Relative hypermethylation in Aid deficient PGCs was confirmed by analysis of individual loci in the genome. Our results reveal that erasure of DNA methylation in the germ line is a global process, hence limiting the potential for transgenerational epigenetic inheritance. Aid deficiency interferes with genome-wide erasure of DNA methylation patterns, suggesting that Aid has a critical function in epigenetic reprogramming and potentially in restricting the inheritance of epimutations in mammals. Comparison of methylation in wild-type and Aid deficient mouse tissues
Project description:Epigenetic reprogramming including demethylation of DNA occurs in mammalian primordial germ cells (PGCs) and in early embryos, and is important for the erasure of imprints and epimutations, and the return to pluripotency. The extent of this reprogramming and its molecular mechanisms are poorly understood. We previously showed that the cytidine deaminases Aid and Apobec1 can deaminate 5-methylcytosine in vitro and in E coli, and in the mouse are expressed in tissues in which demethylation occurs. Here we profiled DNA methylation throughout the genome by unbiased bisulfite Next Generation Sequencing (BS-Seq) in wildtype and Aid deficient PGCs at E13.5. Wildtype PGCs revealed dramatic genome-wide erasure of methylation to a level below that of methylation deficient (Np95-/-) ES cells, with female PGCs being less methylated than male ones. By contrast, Aid deficient PGCs were up to three times more methylated than wildtype ones; this substantial difference occurred throughout the genome, with introns, intergenic regions and transposons being relatively more methylated than exons. Relative hypermethylation in Aid deficient PGCs was confirmed by analysis of individual loci in the genome. Our results reveal that erasure of DNA methylation in the germ line is a global process, hence limiting the potential for transgenerational epigenetic inheritance. Aid deficiency interferes with genome-wide erasure of DNA methylation patterns, suggesting that Aid has a critical function in epigenetic reprogramming and potentially in restricting the inheritance of epimutations in mammals.
Project description:Genome-wide DNA demethylation, including the erasure of genome imprints, in primordial germ cells (PGCs), is critical as a first step for creating the totipotent epigenome in the germ line. Here, we provide evidence that contrary to the prevailing model involving active DNA demethylation, imprint erasure in mouse PGCs occurs in a manner consistent with replication-coupled passive DNA demethylation: PGCs erase imprints during their rapid proliferation with little de novo as well as maintenance DNA methylation potential and no major chromatin alterations. Our findings necessitate the re-evaluation of and provide novel insights into the mechanism of genome-wide DNA demethylation in PGCs.
Project description:Genome-wide DNA demethylation, including the erasure of genome imprints, in primordial germ cells (PGCs), is critical as a first step for creating the totipotent epigenome in the germ line. Here, we provide evidence that contrary to the prevailing model involving active DNA demethylation, imprint erasure in mouse PGCs occurs in a manner consistent with replication-coupled passive DNA demethylation: PGCs erase imprints during their rapid proliferation with little de novo as well as maintenance DNA methylation potential and no major chromatin alterations. Our findings necessitate the re-evaluation of and provide novel insights into the mechanism of genome-wide DNA demethylation in PGCs. We performed expression analysis of primordial germ cells (PGCs) at embryonic days 10.5-13.5. Because the number of PGCs available at these stages were low, cDNAs were amplified by the method that we previously published (Kurimoto et al. 2006, NAR 34: e42 (PMID 16547197)). To include analysis of PGC gene expression at E9.5, we re-normalized the data from our E9.5 PGC samples (GSM744103, GSM744104) from our previous publication (Hayashi et al., 2011, Cell 146: 519-32 (PMD 21820164)) together with the data from this submission.
Project description:During mammalian development DNA methylation patterns need to be reset in primordial germ cells (PGC) and preimplantation embryos. However, many retro-transposons and imprinted genes are resistant to such global epigenetic reprogramming via hitherto undefined mechanisms. Here, we report that some of these sequences are immune to widespread erasure of DNA methylation in the mouse embryonic stem cells (mESCs) lacking de novo DNA methyltransferases. Persistence of DNA methylation at these loci in mESCs depends on the histone H3K9 methyltransferase Setdb1, as deletion of Setdb1 results in reduction of H3K9me3 and DNA methylation levels concomitant with an increase in 5-hydroxymethylation (5hmC). In addition, depletion of H3K9 methyltransferase G9a leads to genome-wide reduction of DNA methylation but to a lesser extent at the above sequences. Taken together, these data reveal that Setdb1 ensures the fidelity of DNA methylation at specific loci in mESCs, which may reflect mechanisms functioning in vivo during key developmental stages. Examination of genome-wide DNA methylation status in 3 cell types.
Project description:During mammalian development DNA methylation patterns need to be reset in primordial germ cells (PGC) and preimplantation embryos. However, many retro-transposons and imprinted genes are resistant to such global epigenetic reprogramming via hitherto undefined mechanisms. Here, we report that some of these sequences are immune to widespread erasure of DNA methylation in the mouse embryonic stem cells (mESCs) lacking de novo DNA methyltransferases. Persistence of DNA methylation at these loci in mESCs depends on the histone H3K9 methyltransferase Setdb1, as deletion of Setdb1 results in reduction of H3K9me3 and DNA methylation levels concomitant with an increase in 5-hydroxymethylation (5hmC). In addition, depletion of H3K9 methyltransferase G9a leads to genome-wide reduction of DNA methylation but to a lesser extent at the above sequences. Taken together, these data reveal that Setdb1 ensures the fidelity of DNA methylation at specific loci in mESCs, which may reflect mechanisms functioning in vivo during key developmental stages. Examination of genome-wide DNA hydroxy-methylation status in 3 cell types.
Project description:During mammalian development DNA methylation patterns need to be reset in primordial germ cells (PGC) and preimplantation embryos. However, many retro-transposons and imprinted genes are resistant to such global epigenetic reprogramming via hitherto undefined mechanisms. Here, we report that some of these sequences are immune to widespread erasure of DNA methylation in the mouse embryonic stem cells (mESCs) lacking de novo DNA methyltransferases. Persistence of DNA methylation at these loci in mESCs depends on the histone H3K9 methyltransferase Setdb1, as deletion of Setdb1 results in reduction of H3K9me3 and DNA methylation levels concomitant with an increase in 5-hydroxymethylation (5hmC). In addition, depletion of H3K9 methyltransferase G9a leads to genome-wide reduction of DNA methylation but to a lesser extent at the above sequences. Taken together, these data reveal that Setdb1 ensures the fidelity of DNA methylation at specific loci in mESCs, which may reflect mechanisms functioning in vivo during key developmental stages. Examination of genome-wide DNA methylation status in 2 cell types.
Project description:DNA methylation reprogramming of primordial germ cells (PGCs) is an essential step that affects the activation and inactivation of certain genes, therefore having a direct impact on the transcriptome of an individual. In this study, we have described the methylome landscape of porcine PGCs, characterizing the genomic elements that resist methylation erasure.
Project description:Genomic imprinting is an allele-specific gene expression system important for mammalian development and function. The molecular basis of genomic imprinting is allele-specific DNA methylation 2. While it is well known that the de novo DNA methyltransferases Dnmt3a/b are responsible for the establishment of genomic imprinting, how the methylation mark is erased during primordial germ cell (PGC) reprogramming remains a mystery. Here we report that Tet1 plays a critical role in the erasure of genomic imprinting. We show that despite their identical genotype, progenies derived from mating between Tet1-KO males and wild-type females exhibit a number of variable phenotypes including placental, fetal and postnatal growth defects, and early embryonic lethality. These defects are, at least in part, caused by the dysregulation of imprinted genes, such as Peg10 and Peg3, which exhibit aberrant hypermethylation in the paternal allele of differential methylated regions (DMRs). RNA-seq reveals extensive dysregulation of imprinted genes in the next generation due to paternal functional loss of Tet1. Genome-wide DNA methylation analysis of E13.5 PGCs and sperm derived from Tet1-KO mice reveals hypermethylation of DMRs of imprinted genes in sperm, which can be traced back to PGCs. Dynamics of methylation change in Tet1-affected sites suggested that Tet1 swipes remaining methylation including imprinted genes at late reprogramming stage. We also revealed that Tet1play a role in paternal imprinting erasure in females germline. Thus, our study establishes a critical function for Tet1 in the erasure of genomic imprinting. Genome-wide DNA methylation analysis of E13.5 PGCs from control and Tet1-KO mice
Project description:Genomic imprinting is an allele-specific gene expression system important for mammalian development and function. The molecular basis of genomic imprinting is allele-specific DNA methylation 2. While it is well known that the de novo DNA methyltransferases Dnmt3a/b are responsible for the establishment of genomic imprinting, how the methylation mark is erased during primordial germ cell (PGC) reprogramming remains a mystery. Here we report that Tet1 plays a critical role in the erasure of genomic imprinting. We show that despite their identical genotype, progenies derived from mating between Tet1-KO males and wild-type females exhibit a number of variable phenotypes including placental, fetal and postnatal growth defects, and early embryonic lethality. These defects are, at least in part, caused by the dysregulation of imprinted genes, such as Peg10 and Peg3, which exhibit aberrant hypermethylation in the paternal allele of differential methylated regions (DMRs). RNA-seq reveals extensive dysregulation of imprinted genes in the next generation due to paternal functional loss of Tet1. Genome-wide DNA methylation analysis of E13.5 PGCs and sperm derived from Tet1-KO mice reveals hypermethylation of DMRs of imprinted genes in sperm, which can be traced back to PGCs. Dynamics of methylation change in Tet1-affected sites suggested that Tet1 swipes remaining methylation including imprinted genes at late reprogramming stage. We also revealed that Tet1play a role in paternal imprinting erasure in females germline. Thus, our study establishes a critical function for Tet1 in the erasure of genomic imprinting. Genome-wide DNA methylation analysis of sperm derived from control and Tet1-KO mice