title: Sox9 is required for precursor cell expansion and extracellular matrix organization during mouse heart valve development.
abstract: Heart valve structures derived from mesenchymal cells of the endocardial cushions (ECs) are composed of highly organized cell lineages and extracellular matrix. Sox9 is a transcription factor required for both early and late stages of cartilage formation that is also expressed in the developing valves of the heart. The requirements for Sox9 function during valvulogenesis and adult valve homeostasis in mice were examined by conditional inactivation of Sox9 using Tie2-cre and Col2a1-cre transgenes. Sox9(flox/flox);Tie2-cre mice die before E14.5 with hypoplastic ECs, reduced cell proliferation and altered extracellular matrix protein (ECM) deposition. Sox9(flox/flox);Col2a1-cre mice die at birth with thickened heart valve leaflets, reduced expression of cartilage-associated proteins and abnormal ECM patterning. Thickened valve leaflets and calcium deposits, characteristic of valve disease, are observed in heterozygous adult Sox9(flox/+);Col2a1-cre mice. Therefore, Sox9 is required early in valve development for expansion of the precursor cell population and later is required for normal expression and distribution of valvular ECM proteins. These data indicate that Sox9 is required for early and late stages of valvulogenesis and identify a potential role for Sox9 in valve disease mechanisms.
authors.affiliation: Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33101, USA.
authors.forename: Joy
authors.initials: J
authors.lastname: Lincoln
authors.forename: Ralf
authors.initials: R
authors.lastname: Kist
authors.forename: Gerd
authors.initials: G
authors.lastname: Scherer
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Yutzey
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D020868:Gene Silencing; D006351:Heart Valves / Q000196:embryology*; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000502:physiology; D051379:Mice; D055758:SOX9 Transcription Factor; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
chemical_list: D016326:Extracellular Matrix Proteins; D006609:High Mobility Group Proteins; D055758:SOX9 Transcription Factor; C527933:Sox9 protein, mouse; D014157:Transcription Factors