title: Muscularizing tissues in the endocardial cushions of the avian heart are characterized by the expression of h1-calponin.
abstract: Muscularization of mesenchymal tissues in the developing heart is an important event in the morphogenesis of the valvuloseptal complex in four-chambered hearts. Perturbation of muscularization has been implicated in the pathogenesis of cardiac malformations in several animal models for congenital heart disease, including the Trisomy 16 mouse and the TGFbeta2 knockout mouse. Studies to unravel the mechanism of muscularization, as well as studies to determine the extent of the process in frequently used animal-model systems for cardiac development, have, thus far, been hampered by the lack of useful differentiation markers for muscularizing tissues, albeit that it had been demonstrated that, in the mouse, muscularizing cells are characterized by an elevated level of smooth muscle actin expression. In this study, we investigated whether muscularization of endocardial cushions in the avian heart is also accompanied by the expression of smooth muscle cell markers. The results presented in this study demonstrate that, in quail and chick, a specific population of muscularizing cells is recognized by the expression of smooth muscle h1-calponin. Interestingly, other genes typically found in smooth muscle cells (e.g., smooth muscle actin and caldesmon) are not expressed in muscularizing tissues. We conclude that muscularization of cushion-derived mesenchymal tissues is associated with a discrete genetic program reflected by the expression of h1-calponin and predict that h1-calponin will prove an invaluable tool in elucidating the regulation of muscularization and other aspects related to this event.
authors.affiliation: Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Iris
authors.initials: I
authors.lastname: Moralez
authors.forename: Aimée
authors.initials: A
authors.lastname: Phelps
authors.forename: Barbara
authors.initials: B
authors.lastname: Riley
authors.forename: Miranda
authors.initials: M
authors.lastname: Raines
authors.forename: Elaine
authors.initials: E
authors.lastname: Wirrig
authors.forename: Brian
authors.initials: B
authors.lastname: Snarr
authors.forename: Jiang-Ping
authors.initials: JP
authors.lastname: Jin
authors.forename: Maurice
authors.initials: M
authors.lastname: Van Den Hoff
authors.forename: Stanley
authors.initials: S
authors.lastname: Hoffman
authors.forename: Andy
authors.initials: A
authors.lastname: Wessels
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D002642:Chick Embryo; D003370:Coturnix / Q000196:embryology; D004699:Endocardium / Q000196:embryology* / Q000378:metabolism; D006321:Heart / Q000196:embryology*; D008840:Microfilament Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D000096985:Calponins
chemical_list: D002135:Calcium-Binding Proteins; D008840:Microfilament Proteins; D000096985:Calponins