title: Brg1 Enables Rapid Growth of the Early Embryo by Suppressing Genes That Regulate Apoptosis and Cell Growth Arrest.
abstract: SWI/SNF (switching/sucrose nonfermenting)-dependent chromatin remodeling establishes coordinated gene expression programs during development, yet important functional details remain to be elucidated. We show that the Brg1 (Brahma-related gene 1; Smarca4) ATPase is globally expressed at high levels during postimplantation development and its conditional ablation, beginning at gastrulation, results in increased apoptosis, growth retardation, and, ultimately, embryonic death. Global gene expression analysis revealed that genes upregulated in Rosa26CreERT2; Brg1(flox/flox) embryos (here referred to as Brg1(d/d) embryos to describe embryos with deletion of the Brg1(flox/flox) alleles) negatively regulate cell cycle progression and cell growth. In addition, the p53 (Trp53) protein, which is virtually undetectable in early wild-type embryos, accumulated in the Brg1(d/d) embryos and activated the p53-dependent pathways. Using P19 cells, we show that Brg1 and CHD4 (chromodomain helicase DNA binding protein 4) coordinate to control target gene expression. Both proteins physically interact and show a substantial overlap of binding sites at chromatin-accessible regions adjacent to genes differentially expressed in the Brg1(d/d) embryos. Specifically, Brg1 deficiency results in reduced levels of the repressive histone H3 lysine K27 trimethylation (H3K27me3) histone mark and an increase in the amount of open chromatin at the regulatory region of the p53 and p21 (Cdkn1a) genes. These results provide insights into the mechanisms by which Brg1 functions, which is in part via the p53 program, to constrain gene expression and facilitate rapid embryonic growth.
authors.affiliation: Chromatin & Gene Expression Section, Epigenetics & Stem Cell Biology Laboratory, NIEHS, NIH, Research Triangle Park, North Carolina, USA.
authors.forename: Ajeet P
authors.initials: AP
authors.lastname: Singh
authors.affiliation: Special Techniques Group, Cellular & Molecular Pathology Branch, NIEHS, NIH, Research Triangle Park, North Carolina, USA.
authors.forename: Julie F
authors.initials: JF
authors.lastname: Foley
authors.affiliation: Chromatin & Gene Expression Section, Epigenetics & Stem Cell Biology Laboratory, NIEHS, NIH, Research Triangle Park, North Carolina, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Rubino
authors.affiliation: Chromatin & Gene Expression Section, Epigenetics & Stem Cell Biology Laboratory, NIEHS, NIH, Research Triangle Park, North Carolina, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Boyle
authors.affiliation: Sciome LLC, Research Triangle Park, North Carolina, USA.
authors.forename: Arpit
authors.initials: A
authors.lastname: Tandon
authors.affiliation: Sciome LLC, Research Triangle Park, North Carolina, USA.
authors.forename: Ruchir
authors.initials: R
authors.lastname: Shah
authors.affiliation: Chromatin & Gene Expression Section, Epigenetics & Stem Cell Biology Laboratory, NIEHS, NIH, Research Triangle Park, North Carolina, USA archer1@niehs.nih.gov.
authors.forename: Trevor K
authors.initials: TK
authors.lastname: Archer
mesh_terms: D000818:Animals; D017209:Apoptosis; D059447:Cell Cycle Checkpoints; D049109:Cell Proliferation; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism*; D047108:Embryonic Development; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D011506:Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C513194:Smarca4 protein, mouse; C509277:Mi-2beta protein, mouse; D004265:DNA Helicases