Myocyte enhancer factor 2C and Nkx2-5 up-regulate each other's expression and initiate cardiomyogenesis in P19 cells.
The Nkx2-5 homeodomain protein plays a key role in cardiomyogenesis. Ectopic expression in frog and zebrafish embryos results in an enlarged myocardium; however, expression of Nkx2-5 in fibroblasts was not able to trigger the development of beating cardiac muscle. In order to examine the ability of Nkx2-5 to modulate endogenous cardiac specific gene expression in cells undergoing early stages of differentiation, P19 cell lines overexpressing Nkx2-5 were differentiated in the absence of Me2SO. Nkx2-5 expression induced cardiomyogenesis in these cultures aggregated without Me2SO. During differentiation into cardiac muscle, Nkx2-5 expression resulted in the activation of myocyte enhancer factor 2C (MEF2C), but not MEF2A, -B, or -D. In order to compare the abilities of Nkx2-5 and MEF2C to induce cellular differentiation, P19 cells overexpressing MEF2C were aggregated in the absence of Me2SO. Similar to Nkx2-5, MEF2C expression initiated cardiomyogenesis, resulting in the up-regulation of Brachyury T, bone morphogenetic protein-4, Nkx2-5, GATA-4, cardiac alpha-actin, and myosin heavy chain expression. These findings indicate the presence of a positive regulatory network between Nkx2-5 and MEF2C and show that both factors can direct early stages of cell differentiation into a cardiomyogenic pathway.
Skerjanc
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Department of Biochemistry, Medical Sciences Building, University of Western Ontario, London, Ontario N6A 5C1, Canada. skerjanc@julian.uwo.ca
Petropoulos
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Ridgeway
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Wilton
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D000199:Actins / Q000096:biosynthesis; D019521:Body Patterning; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis; D018236:Carcinoma, Embryonal; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005326:Fetal Proteins; D050991:GATA4 Transcription Factor; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D064326:MEF2 Transcription Factors; D009206:Myocardium / Q000166:cytology*; D018006:Myogenic Regulatory Factors / Q000096:biosynthesis*; D018995:Myosin Heavy Chains / Q000096:biosynthesis; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000096:biosynthesis; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D000098908:Brachyury Protein
D000199:Actins; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D004121:Dimethyl Sulfoxide; D005326:Fetal Proteins; D050991:GATA4 Transcription Factor; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D018995:Myosin Heavy Chains; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D000098908:Brachyury Protein; C095552:NKX2-5 protein, human; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish