title: Scleraxis is required for cell lineage differentiation and extracellular matrix remodeling during murine heart valve formation in vivo.
abstract: Heart valve structures, derived from mesenchyme precursor cells, are composed of differentiated cell types and extracellular matrix arranged to facilitate valve function. Scleraxis (scx) is a transcription factor required for tendon cell differentiation and matrix organization. This study identified high levels of scx expression in remodeling heart valve structures at embryonic day 15.5 through postnatal stages using scx-GFP reporter mice and determined the in vivo function using mice null for scx. Scx(-/-) mice display significantly thickened heart valve structures from embryonic day 17.5, and valves from mutant mice show alterations in valve precursor cell differentiation and matrix organization. This is indicated by decreased expression of the tendon-related collagen type XIV, increased expression of cartilage-associated genes including sox9, as well as persistent expression of mesenchyme cell markers including msx1 and snai1. In addition, ultrastructure analysis reveals disarray of extracellular matrix and collagen fiber organization within the valve leaflet. Thickened valve structures and increased expression of matrix remodeling genes characteristic of human heart valve disease are observed in juvenile scx(-/-) mice. In addition, excessive collagen deposition in annular structures within the atrioventricular junction is observed. Collectively, our studies have identified an in vivo requirement for scx during valvulogenesis and demonstrate its role in cell lineage differentiation and matrix distribution in remodeling valve structures.
authors.affiliation: Department of Molecular and Cellular Pharmacology, Leonard M Miller School of Medicine, University of Miami, Miami, FL 33101, USA.
authors.forename: Agata K
authors.initials: AK
authors.lastname: Levay
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Peacock
authors.forename: Yinhui
authors.initials: Y
authors.lastname: Lu
authors.forename: Manuel
authors.initials: M
authors.lastname: Koch
authors.forename: Robert B
authors.initials: RB
authors.lastname: Hinton
authors.forename: Karl E
authors.initials: KE
authors.lastname: Kadler
authors.forename: Joy
authors.initials: J
authors.lastname: Lincoln
mesh_terms: D000375:Aging; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002356:Cartilage / Q000196:embryology / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage / Q000235:genetics; D003094:Collagen / Q000378:metabolism; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D005355:Fibrosis; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D006023:Glycoproteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006349:Heart Valve Diseases / Q000196:embryology / Q000378:metabolism; D006351:Heart Valves / Q000196:embryology / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D008648:Mesoderm / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D038081:Organogenesis / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D003094:Collagen; D006023:Glycoproteins; D049452:Green Fluorescent Proteins; D011994:Recombinant Proteins; C504563:Col14a1 protein, mouse; C503815:Scx protein, mouse
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