title: Maintenance of self-renewal ability of mouse embryonic stem cells in the absence of DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b.
abstract: DNA methyltransferases Dnmt1, Dnmt3a and Dnmt3b cooperatively regulate cytosine methylation in CpG dinucleotides in mammalian genomes, providing an epigenetic basis for gene silencing and maintenance of genome integrity. Proper CpG methylation is required for the normal growth of various somatic cell types, indicating its essential role in the basic cellular function of mammalian cells. Previous studies using Dnmt1(-/-) or Dnmt3a(-/-)Dnmt3b(-/-) ES cells, however, have shown that undifferentiated embryonic stem (ES) cells can tolerate hypomethylation for their proliferation. In an attempt to investigate the effects of the complete loss of CpG DNA methyltransferase function, we established mouse ES cells lacking all three of these enzymes by gene targeting. Despite the absence of CpG methylation, as demonstrated by genome-wide methylation analysis, these triple knockout (TKO) ES cells grew robustly and maintained their undifferentiated characteristics. TKO ES cells retained pericentromeric heterochromatin domains marked with methylation at Lys9 of histone H3 and heterochromatin protein-1, and maintained their normal chromosome numbers. Our results indicate that ES cells can maintain stem cell properties and chromosomal stability in the absence of CpG methylation and CpG DNA methyltransferases.
authors.affiliation: Laboratory for Mammalian Epigenetic Studies, Center for Developmental Biology, RIKEN, 2-2-3 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tsumura
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kumaki
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Takebayashi
authors.forename: Morito
authors.initials: M
authors.lastname: Sakaue
authors.forename: Chisa
authors.initials: C
authors.lastname: Matsuoka
authors.forename: Kunitada
authors.initials: K
authors.lastname: Shimotohno
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ishikawa
authors.forename: En
authors.initials: E
authors.lastname: Li
authors.forename: Hiroki R
authors.initials: HR
authors.lastname: Ueda
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Nakayama
authors.forename: Masaki
authors.initials: M
authors.lastname: Okano
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D000090205:DNA Methyltransferase 3A; D015257:DNA-Cytosine Methylases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D000097584:DNA Methyltransferase 3B
chemical_list: D002843:Chromatin; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D015257:DNA-Cytosine Methylases; D000097584:DNA Methyltransferase 3B; C000715535:Dnmt3a protein, mouse; C081573:DNA modification methylase SssI; C000619381:Dnmt1 protein, mouse