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Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts

Title: Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts
Authors: Wang, K
Sengupta, S
Magnani, L
Wilson, CA
Henry, RW
Knott, JG
Item Type: Journal Article
Abstract: During blastocyst formation the segregation of the inner cell mass (ICM) and trophectoderm is governed by the mutually antagonistic effects of the transcription factors Oct4 and Cdx2. Evidence indicates that suppression of Oct4 expression in the trophectoderm is mediated by Cdx2. Nonetheless, the underlying epigenetic modifiers required for Cdx2-dependent repression of Oct4 are largely unknown. Here we show that the chromatin remodeling protein Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts. By employing a combination of RNA interference (RNAi) and gene expression analysis we found that both Brg1 Knockdown (KD) and Cdx2 KD blastocysts exhibit widespread expression of Oct4 in the trophectoderm. Interestingly, in Brg1 KD blastocysts and Cdx2 KD blastocysts, the expression of Cdx2 and Brg1 is unchanged, respectively. To address whether Brg1 cooperates with Cdx2 to repress Oct4 transcription in the developing trophectoderm, we utilized preimplantation embryos, trophoblast stem (TS) cells and Cdx2-inducible embryonic stem (ES) cells as model systems. We found that: (1) combined knockdown (KD) of Brg1 and Cdx2 levels in blastocysts resulted in increased levels of Oct4 transcripts compared to KD of Brg1 or Cdx2 alone, (2) endogenous Brg1 co-immunoprecipitated with Cdx2 in TS cell extracts, (3) in blastocysts Brg1 and Cdx2 co-localize in trophectoderm nuclei and (4) in Cdx2-induced ES cells Brg1 and Cdx2 are recruited to the Oct4 promoter. Lastly, to determine how Brg1 may induce epigenetic silencing of the Oct4 gene, we evaluated CpG methylation at the Oct4 promoter in the trophectoderm of Brg1 KD blastocysts. This analysis revealed that Brg1-dependent repression of Oct4 expression is independent of DNA methylation at the blastocyst stage. In toto, these results demonstrate that Brg1 cooperates with Cdx2 to repress Oct4 expression in the developing trophectoderm to ensure normal development.
Issue Date: 12-May-2010
Date of Acceptance: 22-Apr-2010
URI: http://hdl.handle.net/10044/1/42829
DOI: http://dx.doi.org/10.1371/journal.pone.0010622
ISSN: 1932-6203
Publisher: Public Library of Science
Journal / Book Title: PLOS One
Volume: 5
Issue: 5
Copyright Statement: © 2010 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: Animals
DNA Helicases
DNA Methylation
Gene Expression Regulation, Developmental
Gene Knockdown Techniques
Homeodomain Proteins
Models, Biological
Nuclear Proteins
Octamer Transcription Factor-3
Protein Binding
Protein Transport
Repressor Proteins
Transcription Factors
Transcription, Genetic
General Science & Technology
MD Multidisciplinary
Publication Status: Published
Conference Place: United States
Article Number: e10622
Appears in Collections:Department of Surgery and Cancer