title: TET-mediated DNA demethylation controls gastrulation by regulating Lefty-Nodal signalling.
abstract: Mammalian genomes undergo epigenetic modifications, including cytosine methylation by DNA methyltransferases (DNMTs). Oxidation of 5-methylcytosine by the Ten-eleven translocation (TET) family of dioxygenases can lead to demethylation. Although cytosine methylation has key roles in several processes such as genomic imprinting and X-chromosome inactivation, the functional significance of cytosine methylation and demethylation in mouse embryogenesis remains to be fully determined. Here we show that inactivation of all three Tet genes in mice leads to gastrulation phenotypes, including primitive streak patterning defects in association with impaired maturation of axial mesoderm and failed specification of paraxial mesoderm, mimicking phenotypes in embryos with gain-of-function Nodal signalling. Introduction of a single mutant allele of Nodal in the Tet mutant background partially restored patterning, suggesting that hyperactive Nodal signalling contributes to the gastrulation failure of Tet mutants. Increased Nodal signalling is probably due to diminished expression of the Lefty1 and Lefty2 genes, which encode inhibitors of Nodal signalling. Moreover, reduction in Lefty gene expression is linked to elevated DNA methylation, as both Lefty-Nodal signalling and normal morphogenesis are largely restored in Tet-deficient embryos when the Dnmt3a and Dnmt3b genes are disrupted. Additionally, a point mutation in Tet that specifically abolishes the dioxygenase activity causes similar morphological and molecular abnormalities as the null mutation. Taken together, our results show that TET-mediated oxidation of 5-methylcytosine modulates Lefty-Nodal signalling by promoting demethylation in opposition to methylation by DNMT3A and DNMT3B. These findings reveal a fundamental epigenetic mechanism featuring dynamic DNA methylation and demethylation crucial to regulation of key signalling pathways in early body plan formation.
authors.affiliation: State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China.|Shanghai Key Laboratory of Molecular Andrology, Institute of Biochemistry and Cell Biology, Chinese Academy of Science, Shanghai 200031, China.
authors.forename: Hai-Qiang
authors.initials: HQ
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China.|Shanghai Key Laboratory of Molecular Andrology, Institute of Biochemistry and Cell Biology, Chinese Academy of Science, Shanghai 200031, China.
authors.forename: Bang-An
authors.initials: BA
authors.lastname: Wang
authors.affiliation: Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China.|Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing 100871, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China.|Shanghai Key Laboratory of Molecular Andrology, Institute of Biochemistry and Cell Biology, Chinese Academy of Science, Shanghai 200031, China.
authors.forename: Jia-Jia
authors.initials: JJ
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China.|Shanghai Key Laboratory of Molecular Andrology, Institute of Biochemistry and Cell Biology, Chinese Academy of Science, Shanghai 200031, China.
authors.forename: Guo-Chun
authors.initials: GC
authors.lastname: Zhu
authors.affiliation: School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China.
authors.forename: Mei-Ling
authors.initials: ML
authors.lastname: Sun
authors.affiliation: Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ge
authors.affiliation: Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China.|Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing 100871, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Chapman
authors.affiliation: Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China.|Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing 100871, China.
authors.forename: Fuchou
authors.initials: F
authors.lastname: Tang
authors.affiliation: Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China.|Shanghai Key Laboratory of Molecular Andrology, Institute of Biochemistry and Cell Biology, Chinese Academy of Science, Shanghai 200031, China.|School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China.
authors.forename: Guo-Liang
authors.initials: GL
authors.lastname: Xu
mesh_terms: D044503:5-Methylcytosine / Q000378:metabolism; D000818:Animals; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D000090205:DNA Methyltransferase 3A; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D049308:Dioxygenases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000196:embryology / Q000201:enzymology / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D044127:Epigenesis, Genetic; D005260:Female; D054262:Gastrulation / Q000235:genetics; D055458:Left-Right Determination Factors / Q000378:metabolism*; D008297:Male; D008648:Mesoderm / Q000196:embryology / Q000378:metabolism; D051379:Mice; D055457:Nodal Protein / Q000378:metabolism*; D010084:Oxidation-Reduction; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D000097584:DNA Methyltransferase 3B
chemical_list: D044503:5-Methylcytosine; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D004268:DNA-Binding Proteins; D049308:Dioxygenases; D055458:Left-Right Determination Factors; D055457:Nodal Protein; D011518:Proto-Oncogene Proteins; D000097584:DNA Methyltransferase 3B; C000715535:Dnmt3a protein, mouse; C526008:Nodal protein, mouse; C540839:TET1 protein, mouse; C551914:Tet2 protein, mouse; C551915:Tet3 protein, mouse