Premium
Dynamics of genomic 5‐hydroxymethylcytosine during mouse oocyte growth
Author(s) -
Sakashita Akihiko,
Kobayashi Hisato,
Wakai Takuya,
Sotomaru Yusuke,
Hata Kenichiro,
Kono Tomohiro
Publication year - 2014
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/gtc.12164
Subject(s) - 5 hydroxymethylcytosine , biology , zygote , dna demethylation , oocyte , retrotransposon , dna methylation , embryo , genetics , genomic imprinting , epigenetics , andrology , embryogenesis , microbiology and biotechnology , genome , gene expression , transposable element , gene , medicine
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.