Abstract
The epigenomes of early mammalian embryos are extensively reprogrammed to acquire a totipotent developmental potential. A major initial event in this reprogramming is the active loss/demethylation of 5-methylcytosine (5mC) in the zygote. Here, we report on findings that link this active demethylation to molecular mechanisms. We detect 5-hydroxymethylcytosine (5hmC) as a novel modification in mouse, bovine and rabbit zygotes. On zygotic development 5hmC accumulates in the paternal pronucleus along with a reduction of 5mC. A knockdown of the 5hmC generating dioxygenase Tet3 simultaneously affects the patterns of 5hmC and 5mC in the paternal pronucleus. This finding links the loss of 5mC to its conversion into 5hmC. The maternal pronucleus seems to be largely protected against this mechanism by PGC7/Dppa3/Stella, as in PGC7 knockout zygotes 5mC also becomes accessible to oxidation into 5hmC. In summary, our data suggest an important role of 5hmC and Tet3 for DNA methylation reprogramming processes in the mammalian zygote.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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5-Methylcytosine / metabolism*
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Animals
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Cattle
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Cell Nucleus / genetics*
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Cell Nucleus / metabolism
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Chromosomal Proteins, Non-Histone
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Cytosine / analogs & derivatives*
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Cytosine / metabolism
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DNA Methylation
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Dioxygenases
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Embryo, Mammalian / cytology
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Embryo, Mammalian / metabolism*
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Epigenomics*
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Female
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Fertilization in Vitro
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Gene Expression Regulation, Developmental
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Gene Knockdown Techniques
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Mammals / embryology
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Mammals / genetics
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Mammals / metabolism*
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Mice
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Mice, Knockout
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Nuclear Transfer Techniques
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Oxidation-Reduction
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism
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Rabbits
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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Sex Factors
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Zygote / cytology
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Zygote / metabolism
Substances
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Chromosomal Proteins, Non-Histone
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DNA-Binding Proteins
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Dppa3 protein, mouse
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Proto-Oncogene Proteins
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Repressor Proteins
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5-hydroxymethylcytosine
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5-Methylcytosine
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Cytosine
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Dioxygenases
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Tet3 protein, mouse