Transient depletion of xDnmt1 leads to premature gene activation in Xenopus embryos.
In Xenopus laevis zygotic transcription begins at the midblastula transition (MBT). Prior to this the genome is organized into chromatin that facilitates rapid cycles of DNA replication but not transcription. Here we demonstrate that DNA methylation contributes to the overall transcriptional silencing before MBT. Transient depletion of the maternal DNA methyltransferase (xDnmt1) by anti sense RNA during cleavage stages is associated with a decrease in the genomic 5-methyl-cytosine content and leads to the activation of zygotic transcription approximately two cell cycles earlier than normal. Hypomethylation allows the early expression of mesodermal marker genes such as Xbra, Cerberus, and Otx2, which are subsequently down-regulated during gastrulation of the xDnmt1-depleted embryos. The temporal switch in gene expression may account for the appearance of body plan defects that we observe. Loss of xDnmt1 can be rescued by the coinjection of mouse or human Dnmt1 protein. These results demonstrate that DNA methylation has a role in the regulation of immediately early genes in Xenopus at MBT.
Stancheva
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Genes and Development Group, Department of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD Scotland, UK.
Meehan
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D044503:5-Methylcytosine; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002454:Cell Differentiation; D003596:Cytosine / Q000031:analogs & derivatives / Q000737:chemistry; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004625:Embryo, Nonmammalian; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008845:Microinjections; D016372:RNA, Antisense / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020825:T-Box Domain Proteins / Q000378:metabolism; D015533:Transcriptional Activation; D029867:Xenopus Proteins; D014982:Xenopus laevis
D016372:RNA, Antisense; D020825:T-Box Domain Proteins; C116765:TBXT protein, Xenopus; D029867:Xenopus Proteins; D044503:5-Methylcytosine; D003596:Cytosine; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse