title: DNA methylation is dispensable for the growth and survival of the extraembryonic lineages.
abstract: DNA methylation regulates development and many epigenetic processes in mammals, and it is required for somatic cell growth and survival. In contrast, embryonic stem (ES) cells can self-renew without DNA methylation. It remains unclear whether any lineage-committed cells can survive without DNA-methylation machineries. Unlike in somatic cells, DNA methylation is dispensable for imprinting and X-inactivation in the extraembryonic lineages. In ES cells, DNA methylation prevents differentiation into the trophectodermal fate. Here, we created triple-knockout (TKO) mouse embryos deficient for the active DNA methyltransferases Dnmt1, Dnmt3a, and Dnmt3b (TKO) by nuclear transfer (NT), and we examined their development. In chimeric TKO-NT and WT embryos, few TKO cells were found in the embryo proper, but they contributed to extraembryonic tissues. TKO ES cells showed increasing cell death during their differentiation into epiblast lineages, but not during differentiation into extraembryonic lineages. Furthermore, we successfully established trophoblastic stem cells (ntTS cells) from TKO-NT blastocysts. These TKO ntTS cells could self-renew, and they retained the fundamental gene expression patterns of stem cells. Our findings indicated that extraembryonic-lineage cells can survive and proliferate in the absence of DNA methyltransferases and that a cell's response to the stress of epigenomic damage is cell type dependent.
authors.affiliation: Laboratory for Mammalian Epigenetic Studies, Center for Developmental Biology, RIKEN, 2-2-3, Minatojima-minamimachi, Kobe, Hyogo, 650-0047, Japan.
authors.forename: Morito
authors.initials: M
authors.lastname: Sakaue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohta
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kumaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Oda
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sakaide
authors.forename: Chisa
authors.initials: C
authors.lastname: Matsuoka
authors.forename: Akiko
authors.initials: A
authors.lastname: Yamagiwa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Niwa
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Wakayama
authors.forename: Masaki
authors.initials: M
authors.lastname: Okano
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D047108:Embryonic Development / Q000235:genetics*; D053595:Embryonic Stem Cells / Q000502:physiology*; D044127:Epigenesis, Genetic; D051379:Mice; D000097584:DNA Methyltransferase 3B
chemical_list: D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D000097584:DNA Methyltransferase 3B; C000715535:Dnmt3a protein, mouse; C000619381:Dnmt1 protein, mouse