title: Extraembryonic signals under the control of MGA, Max, and Smad4 are required for dorsoventral patterning.
abstract: In vertebrates, extraembryonic tissues can act as signaling centers that impose a reproducible pattern of cell types upon the embryo. Here, we show that the zebrafish yolk syncytial layer (YSL) secretes a ventralizing signal during gastrulation. This activity is mediated by Bmp2b/Swirl (Swr) expressed under the control of Max's giant associated protein (MGA) and its binding partners, Max and Smad4. MGA coimmunoprecipitates with both Max and Smad4 in embryo extracts, and the three proteins form a complex in vitro. Furthermore, all three proteins bind to a DNA fragment upstream of the bmp2b transcription start site. Targeted depletion of MGA, its binding partners, or Bmp2b/Swr from the YSL reduces BMP signaling throughout the embryo, resulting in a mildly dorsalized phenotype. We conclude that MGA, Max, and Smad4 act in the extraembryonic YSL to initiate a positive feedback loop of Bmp signaling within the embryo.
authors: Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA.
authors: Yuhua
authors: Y
authors: Sun
authors: Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA.
authors: Wei-Chia
authors: WC
authors: Tseng
authors: Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA.
authors: Xiang
authors: X
authors: Fan
authors: Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA.
authors: Rebecca
authors: R
authors: Ball
authors: Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA. Electronic address: dougan@uga.edu.
authors: Scott T
authors: ST
authors: Dougan
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D019521:Body Patterning; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D050436:Regulatory Elements, Transcriptional; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D055396:Bone Morphogenetic Protein 2; C499328:Max protein, zebrafish; D012333:RNA, Messenger; D051901:Smad4 Protein; D029961:Zebrafish Proteins; C405936:bmp2b protein, zebrafish; C487788:mgaa protein, zebrafish; C490809:smad4a protein, zebrafish