title: Dynamics of genomic 5-hydroxymethylcytosine during mouse oocyte growth.
abstract: Recent studies of the demethylation process in murine zygotes have shown that 5-methylcytosine (5mC) is first converted into 5-hydroxymethylcytosine (5hmC) or further-oxidized cytosines in the paternal genome by the maternal ten-eleven translocation 3 (TET3) enzyme. This process is crucial for normal embryogenesis, and our aim was to elucidate the effect of Tet3 on the maternal genome during female germ-line development. Immunofluorescence analysis showed that 5hmC was clearly present in fully grown oocytes but not in nongrowing and early growth-stage oocytes. The 5hmC in the maternal genome was clearly detectable in DNA methyltransferase 3-like enzyme (Dnmt3L)-null oocytes and their fertilized zygotes, although Dnmt3L is essential for DNA methylation in oocytes. An analysis using an enzyme digestion-based method showed that 5hmC was present in LTR retrotransposons from the late growth period of oocytes. Quantitative RT-PCR analysis showed that Tet3 expression was enhanced during oocyte growth and exhibited an approximately 40-fold increase between nongrowing and fully grown oocytes. Our results show that 5hmC is generated since the oocyte growth stage, accompanied by up-regulation of Tet3; 5hmC is located mainly in LTR retrotransposons, indicating that 5hmC generated in growth-stage oocytes is responsible for genomewide demethylation after fertilization.
authors.affiliation: Department of BioScience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 156-8502, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Sakashita
authors.forename: Hisato
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Takuya
authors.initials: T
authors.lastname: Wakai
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sotomaru
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Hata
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kono
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives; D000818:Animals; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D049308:Dioxygenases; D005260:Female; D016678:Genome; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000254:growth & development* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D015053:Zygote / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D003596:Cytosine; D049308:Dioxygenases; C551915:Tet3 protein, mouse; C498796:Dnmt3l protein, mouse; D004248:DNA (Cytosine-5-)-Methyltransferases