title: Sequential programs of retinoic acid synthesis in the myocardial and epicardial layers of the developing avian heart.
abstract: Endogenous patterns of retinoic acid (RA) signaling in avian cardiac morphogenesis were characterized by localized expression of a key RA-synthetic enzyme, RALDH2, which displayed a biphasic pattern during heart development. RALDH2 immunoreactivity was initially apparent posterior to Hensen's node of stage 5-6 embryos and subsequently in somites and unsegmented paraxial and lateral plate mesoderm overlapping atrial precursors in the cardiogenic plate of stage 9- embryos. Initial RALDH2 synthesis in the posterior myocardium coincided with activation of the AMHC1 gene, a RA-responsive marker of inflow heart segments. A wave of RALDH2 synthesis then swept the myocardium in a posterior-to-anterior direction, reaching the outflow tract by stage 13, then fading from the myocardial layer. The second phase of RALDH2 expression, initiated at stage 18 in the proepicardial organ, persisted in migratory epicardial cells that completely enveloped the heart by stage 24. Early restriction of RALDH2 expression to the posterior cardiogenic plate, overlapping RA-inducible gene activation, provides evidence for commitment of posterior avian heart segments by localized production of RA, whereas subsequent RALDH2 expression exclusively in the migratory epicardium suggests a role for the morphogen in ventricular expansion and morphogenesis of underlying myocardial tissues.
authors.affiliation: Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, 02129, USA.
authors.forename: J
authors.initials: J
authors.lastname: Xavier-Neto
authors.forename: M D
authors.initials: MD
authors.lastname: Shapiro
authors.forename: L
authors.initials: L
authors.lastname: Houghton
authors.forename: N
authors.initials: N
authors.lastname: Rosenthal
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D000818:Animals; D024743:Atrial Myosins; D030161:Avian Proteins; D005075:Biological Evolution; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009206:Myocardium / Q000378:metabolism*; D018995:Myosin Heavy Chains; D009218:Myosins / Q000235:genetics; D010496:Pericardium / Q000196:embryology* / Q000378:metabolism*; D011784:Quail / Q000196:embryology; D050697:Retinal Dehydrogenase; D015398:Signal Transduction; D015533:Transcriptional Activation; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D030161:Avian Proteins; D014212:Tretinoin; D000445:Aldehyde Oxidoreductases; D050697:Retinal Dehydrogenase; D024743:Atrial Myosins; C094463:AMHC1 protein, chicken; D018995:Myosin Heavy Chains; D009218:Myosins