title: Hedgehog signaling is required for differentiation of endocardial progenitors in zebrafish.
abstract: Endocardial cells form the inner endothelial layer of the heart tube, surrounded by the myocardium. Signaling pathways that regulate endocardial cell specification and differentiation are largely unknown and the origin of endocardial progenitors is still being debated. To study pathways that regulate endocardial differentiation in a zebrafish model system, we isolated zebrafish NFATc1 homolog which is expressed in endocardial but not vascular endothelial cells. We further demonstrate that Hedgehog (Hh) but not VegfA or Notch signaling is required for early endocardial morphogenesis. Pharmacological inhibition of Hh signaling with cyclopamine treatment resulted in nearly complete loss of the endocardial marker expression. Simultaneous knockdown of the two zebrafish sonic hedgehog homologs, shh and twhh or Hh co-receptor smoothened (smo) resulted in similar defects in endocardial morphogenesis. Inhibition of Hh signaling resulted in the loss of fibronectin (fn1) expression in the presumptive endocardial progenitors as early as the 10-somite stage which suggests that Hh signaling is required for the earliest stages of endocardial specification. We further show that the endoderm plays a critical role in migration but not specification or differentiation of the endocardial progenitors while notochord-derived Hh is a likely source for the specification and differentiation signal. Mosaic analysis using cell transplantation shows that Smo function is required cell-autonomously within endocardial progenitor cells. Our results argue that Hh provides a critical signal to induce the specification and differentiation of endocardial progenitors.
authors: Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, USA.
authors: Kuan Shen
authors: KS
authors: Wong
authors: Kira
authors: K
authors: Rehn
authors: Sharina
authors: S
authors: Palencia-Desai
authors: Vikram
authors: V
authors: Kohli
authors: Wynn
authors: W
authors: Hunter
authors: Juli D
authors: JD
authors: Uhl
authors: Megan S
authors: MS
authors: Rost
authors: Saulius
authors: S
authors: Sumanas
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004699:Endocardium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D004707:Endoderm / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D009024:Morphogenesis / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D009672:Notochord / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D059008:Time-Lapse Imaging; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014704:Veratrum Alkaloids / Q000494:pharmacology; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D005353:Fibronectins; D053823:Hedgehog Proteins; D050778:NFATC Transcription Factors; D051880:Receptors, Notch; D042461:Vascular Endothelial Growth Factor A; D014704:Veratrum Alkaloids; D029961:Zebrafish Proteins; C000541:cyclopamine