title: Parietal endoderm secreted SPARC promotes early cardiomyogenesis in vitro.
abstract: Cardiomyogenesis proceeds in the presence of signals emanating from extra-embryonic lineages emerging before and during early eutherian gastrulation. In embryonic stem cell derived embryoid bodies, primitive endoderm gives rise to visceral and parietal endoderm. Parietal endoderm undergoes an epithelial to mesenchymal transition shortly before first cardiomyocytes start to contract rhythmically. Here, we demonstrate that Secreted Protein, Acidic, Rich in Cysteine, SPARC, predominantly secreted by mesenchymal parietal endoderm specifically promotes early myocardial cell differentiation in embryoid bodies. SPARC enhanced the expression of bmp2 and nkx2.5 in embryoid bodies and fetal cardiomyocytes. Inhibition of either SPARC or Bmp2 attenuated in both cases cardiomyogenesis and downregulated nkx2.5 expression. Thus, SPARC directly affects cardiomyogenesis, modulates Bmp2 signaling, and contributes to a positive autoregulatory loop of Bmp2 and Nkx2.5 in cardiomyocytes.
authors.affiliation: Max F. Perutz Laboratories, University Institutes at the Vienna Biocenter, Department of Medical Biochemistry, Division of Molecular Cell Biology, Medical University of Vienna, Dr. Bohrgasse 9, A1030 Vienna, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Stary
authors.forename: Waltraud
authors.initials: W
authors.lastname: Pasteiner
authors.forename: Alexandra
authors.initials: A
authors.lastname: Summer
authors.forename: Astrid
authors.initials: A
authors.lastname: Hrdina
authors.forename: Andreas
authors.initials: A
authors.lastname: Eger
authors.forename: Georg
authors.initials: G
authors.lastname: Weitzer
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D004707:Endoderm / Q000166:cytology / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000502:physiology; D051379:Mice; D024510:Muscle Development / Q000235:genetics; D032383:Myocytes, Cardiac / Q000378:metabolism; D015676:Osteonectin / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C484469:Nkx2-5 protein, mouse; D015676:Osteonectin; D014157:Transcription Factors; D016212:Transforming Growth Factor beta