title: Further characterization of BC3H1 myogenic cells reveals lack of p53 activity and underexpression of several p53 regulated and extracellular matrix-associated gene products.
abstract: To catalog factors that may contribute to the completion of myogenesis, we have been looking for molecular differences between BC3H1 and C2C12 cells. Cells of the BC3H1 tumor line, though myogenic, are nonfusing, and withdraw from the cell cycle only reversibly, whereas cells of the C2C12 line fuse, differentiate terminally, and express several muscle-specific gene products that BC3H1 cells do not. Relative to C2C12 cells, BC3H1 cells underaccumulated cyclin-dependent kinase inhibitor p21 and underaccumulated transcripts for p21, GADD45, CDO, decorin, osteopontin, H19, fibronectin, and thrombospondin-1 (tsp-1). Levels of accumulation of H19, tsp-1, and larger isoforms of fibronectin messenger ribonucleic acid (mRNA) were found to increase in response to expression of myogenic regulatory factors as shown by their accumulation in differentiated myogenically converted 10T1/2 cells but not in 10T1/2 fibroblasts. BC3H1s accumulated a temperature-insensitive, geldanamycin-sensitive, misfolded form of p53 incapable of transactivating a p53 responsive reporter, consistent with underexpression of p21, GADD45, and tsp-1. BC3H1 and C2C12 cells were similar with respect to upregulation of p27 protein, downregulation of mitogen-activated protein kinase phosphatase-1 (MKP-1) protein, upregulation of retinoblastoma (Rb) mRNA, and nuclear localization of hypophosphorylated Rb. Cells of both lines expressed the muscle-specific 1b isoform of MEF2D. Although nonfusing in the short term, after more than 18 d in differentiation medium, some cultures of BC3H1 cells formed viable multinucleated cells in which the nuclei did not reinitiate synthesis of DNA in response to serum. Our findings suggest participation of tsp-1 and specific isoforms of fibronectin in myogenesis and suggest additional avenues of research in myogenesis and oncogenesis.
authors.affiliation: Department of Biological Sciences, California State University, 5151 State University Drive, Los Angeles, California 90032, USA. ssharp@calstatela.edu
authors.forename: Sandra B
authors.initials: SB
authors.lastname: Sharp
authors.forename: Maria
authors.initials: M
authors.lastname: Villalvazo
authors.forename: Mickey
authors.initials: M
authors.lastname: Huang
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Gonzalez
authors.forename: Irania
authors.initials: I
authors.lastname: Alarcon
authors.forename: Matthew
authors.initials: M
authors.lastname: Bahamonde
authors.forename: Diane M
authors.initials: DM
authors.lastname: D'Agostin
authors.forename: Sagar
authors.initials: S
authors.lastname: Damle
authors.forename: Alex
authors.initials: A
authors.lastname: Espinosa
authors.forename: Seog J
authors.initials: SJ
authors.lastname: Han
authors.forename: Jessica
authors.initials: J
authors.lastname: Liu
authors.forename: Paula
authors.initials: P
authors.lastname: Navarro
authors.forename: Hugo
authors.initials: H
authors.lastname: Salguero
authors.forename: Jina
authors.initials: J
authors.lastname: Son
authors.forename: Son
authors.initials: S
authors.lastname: Vu
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009132:Muscles / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53