title: Pou5f1 contributes to dorsoventral patterning by positive regulation of vox and modulation of fgf8a expression.
abstract: Pou5f1/Oct-4 in mice is required for maintenance of embryonic pluripotent cell populations. Zebrafish pou5f1 maternal-zygotic mutant embryos (spiel ohne grenzen; MZspg) lack endoderm and have gastrulation and dorsoventral patterning defects. A contribution of Pou5f1 to the control of bmp2b, bmp4 and vox expression has been suggested, however the mechanisms remained unclear and are investigated in detail here. Low-level overexpression of a Pou5f1-VP16 activator fusion protein can rescue dorsalization in MZspg mutants, indicating that Pou5f1 acts as a transcriptional activator during dorsoventral patterning. Overexpression of larger quantities of Pou5f1-VP16 can ventralize wild-type embryos, while overexpression of a Pou5f1-En repressor fusion protein can dorsalize embryos. Lack of Pou5f1 causes a transient upregulation of fgf8a expression after mid-blastula transition, providing a mechanism for delayed activation of bmp2b in MZspg embryos. Overexpression of the Pou5f1-En repressor induces fgf8, suggesting an indirect mechanism of Pou5f1 control of fgf8a expression. Transcription of vox is strongly activated by Pou5f1-VP16 even when translation of zygotically expressed transcripts is experimentally inhibited by cycloheximide. In contrast, bmp2b and bmp4 are not activated under these conditions. We show that Pou5f1 binds to phylogenetically conserved Oct/Pou5f1 sites in the vox promoter, both in vivo (ChIP) and in vitro. Our data reveals a set of direct and indirect interactions of Pou5f1 with the BMP dorsoventral patterning network that serve to fine-tune dorsoventral patterning mechanisms and coordinate patterning with developmental timing.
authors.affiliation: Developmental Biology, Faculty of Biology, University of Freiburg, Hauptstrasse 1, Freiburg, Germany.
authors.forename: Heinz-Georg
authors.initials: HG
authors.lastname: Belting
authors.forename: Björn
authors.initials: B
authors.lastname: Wendik
authors.forename: Karen
authors.initials: K
authors.lastname: Lunde
authors.forename: Manuel
authors.initials: M
authors.lastname: Leichsenring
authors.forename: Rebecca
authors.initials: R
authors.lastname: Mössner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Driever
authors.forename: Daria
authors.initials: D
authors.lastname: Onichtchouk
mesh_terms: D000818:Animals; D001665:Binding Sites; D019521:Body Patterning; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics; D055419:Bone Morphogenetic Protein 7 / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D050814:Octamer Transcription Factor-3 / Q000378:metabolism / Q000502:physiology*; D010802:Phylogeny; D012097:Repressor Proteins / Q000235:genetics*; D015398:Signal Transduction; D015533:Transcriptional Activation; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
chemical_list: D055396:Bone Morphogenetic Protein 2; D055419:Bone Morphogenetic Protein 7; D018398:Homeodomain Proteins; D050814:Octamer Transcription Factor-3; C085437:Pou5f3 protein, zebrafish; D012097:Repressor Proteins; C434249:Vox protein, zebrafish; D029961:Zebrafish Proteins; C405936:bmp2b protein, zebrafish; C525826:bmp7a protein, zebrafish; C517774:fgf8a protein, zebrafish; C434250:vent protein, zebrafish; D005346:Fibroblast Growth Factors; D003513:Cycloheximide