A POU protein regulates mesodermal competence to FGF in Xenopus.
XLPOU91, a POU-homeobox gene is expressed in a narrow window during early Xenopus development. We show that ectopic expression of XLPOU91 RNA causes severe posterior truncations in embryos without inhibiting the formation of Spemann's organizer. Ectopic XLPOU91 expression also inhibits mesoderm induction by fibroblast growth factor (FGF) and activin in animal cap explants. Using antisense RNA, we depleted endogenous XLPOU91 protein in animal caps. Gastrula-stage animal caps expressing XLPOU91 antisense RNA do not lose competence to FGF, unlike controls, these animal caps express XBra after FGF treatment. Endogenous XLPOU91 levels are peaking when FGF mesoderm-inducing competence is lost in animal caps. Thus XLPOU91 protein may act as a competence switch during early development, as XLPOU91 levels increase in the embryo, the mesoderm response to FGF is lost.
Henig
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Department of Biochemistry, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
Elias
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Frank
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D000818:Animals; D001368:Axis, Cervical Vertebra / Q000187:drug effects / Q000196:embryology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000201:enzymology; D004627:Embryonic Induction / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008648:Mesoderm / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics*
D018398:Homeodomain Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C112436:pou5f3.1 protein, Xenopus; D016222:Fibroblast Growth Factor 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases