title: Osteoactivin induces transdifferentiation of C2C12 myoblasts into osteoblasts.
abstract: Osteoactivin (OA) is a novel osteogenic factor important for osteoblast differentiation and function. Previous studies showed that OA stimulates matrix mineralization and transcription of osteoblast specific genes required for differentiation. OA plays a role in wound healing and its expression was shown to increase in post fracture calluses. OA expression was reported in muscle as OA is upregulated in cases of denervation and unloading stress. The regulatory mechanisms of OA in muscle and bone have not yet been determined. In this study, we examined whether OA plays a role in transdifferentiation of C2C12 myoblast into osteoblasts. Infected C2C12 with a retroviral vector overexpressing OA under the CMV promoter were able to transdifferentiate from myoblasts into osteoblasts. Immunofluorescence analysis showed that skeletal muscle marker MF-20 was severely downregulated in cells overexpressing OA and contained significantly less myotubes compared to uninfected control. C2C12 myoblasts overexpressing OA showed an increase in expression of bone specific markers such as alkaline phosphatase and alizarin red staining, and also showed an increase in Runx2 protein expression. We also detected increased levels of phosphorylated focal adhesion kinase (FAK) in C2C12 myoblasts overexpressing OA compared to control. Taken together, our results suggest that OA is able to induce transdifferentiation of myoblasts into osteoblasts through increasing levels of phosphorylated FAK.
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, Ohio; School of Biomedical Sciences, Kent State University, Kent, Ohio.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Sondag
authors.forename: Sibel
authors.initials: S
authors.lastname: Salihoglu
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Lababidi
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Crowder
authors.forename: Fouad M
authors.initials: FM
authors.lastname: Moussa
authors.forename: Samir M
authors.initials: SM
authors.lastname: Abdelmagid
authors.forename: Fayez F
authors.initials: FF
authors.lastname: Safadi
mesh_terms: D000469:Alkaline Phosphatase / Q000096:biosynthesis; D000818:Animals; D002460:Cell Line; D054338:Cell Transdifferentiation / Q000235:genetics*; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000096:biosynthesis; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D005136:Eye Proteins; C445671:Gpnmb protein, mouse; D008562:Membrane Glycoproteins; D051416:Focal Adhesion Protein-Tyrosine Kinases; D000469:Alkaline Phosphatase