title: Essential role for de novo DNA methyltransferase Dnmt3a in paternal and maternal imprinting.
abstract: Imprinted genes are epigenetically marked during gametogenesis so that they are exclusively expressed from either the paternal or the maternal allele in offspring. Imprinting prevents parthenogenesis in mammals and is often disrupted in congenital malformation syndromes, tumours and cloned animals. Although de novo DNA methyltransferases of the Dnmt3 family are implicated in maternal imprinting, the lethality of Dnmt3a and Dnmt3b knockout mice has precluded further studies. We here report the disruption of Dnmt3a and Dnmt3b in germ cells, with their preservation in somatic cells, by conditional knockout technology. Offspring from Dnmt3a conditional mutant females die in utero and lack methylation and allele-specific expression at all maternally imprinted loci examined. Dnmt3a conditional mutant males show impaired spermatogenesis and lack methylation at two of three paternally imprinted loci examined in spermatogonia. By contrast, Dnmt3b conditional mutants and their offspring show no apparent phenotype. The phenotype of Dnmt3a conditional mutants is indistinguishable from that of Dnmt3L knockout mice, except for the discrepancy in methylation at one locus. These results indicate that both Dnmt3a and Dnmt3L are required for methylation of most imprinted loci in germ cells, but also suggest the involvement of other factors.
authors.affiliation: Division of Human Genetics, Department of Integrated Genetics, National Institute of Genetics, Research Organization of Information and Systems, Mishima 411-8540, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kaneda
authors.forename: Masaki
authors.initials: M
authors.lastname: Okano
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Hata
authors.forename: Takashi
authors.initials: T
authors.lastname: Sado
authors.forename: Naomi
authors.initials: N
authors.lastname: Tsujimoto
authors.forename: En
authors.initials: E
authors.lastname: Li
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000483:Alleles; D000818:Animals; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D020964:Embryo Loss / Q000235:genetics; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D020043:Genes, Essential / Q000235:genetics*; D018392:Genomic Imprinting / Q000235:genetics*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D016296:Mutagenesis / Q000235:genetics; D010641:Phenotype; D012727:Sex Characteristics; D013091:Spermatogenesis; D013093:Spermatogonia / Q000166:cytology / Q000378:metabolism
chemical_list: C000717967:DNMT3A protein, human; C000715535:Dnmt3a protein, mouse; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A