Proteomic characterization of primary cultured myocytes in a fish model at different myogenesis stages

Myogenesis is a complex two-phase process of proliferation and differentiation, which seems to be greatly conserved in vertebrates. For the first time in fish, we identify the changes that occur in the proteome during this process in a gilthead sea bream (Sparus aurata) myocyte primary cell culture (on days 4, 8 and 12), using 2-D gel electrophoresis and LC-MS/MS. A significant increase of myogenin expression at day 8 marked the transition from proliferation to differentiation. Of the 898 spots in the proteome analysis, the 25 protein spots overexpressed on day 4 and the 15 protein spots overexpressed on day 8 indicate the end of proliferation and the beginning of differentiation, respectively. Proliferation was characterized by enrichment of proteins involved in actin cytoskeleton remodelling and in cellular metabolic processes (transcription, ubiquitination, response to stress and glucose metabolism). During differentiation, 41 proteins were overexpressed and 51 underexpressed; many of them related to biosynthetic processes (RNA and protein synthesis and folding, and pentose pathways), terminal myotube formation and muscle contraction. The main cellular processes of both phases of muscle development in fish are similar with those observed in mammals but extended in time, allowing sequential studies of myogenesis.