Cloning and expression of the porcine myogenin gene

Myogenin is a member of the myoD family of myogenic regulatory factors which direct the initiation of myogenesis during skeletal muscle development. Myogenin is responsible for the differentiation of proliferating myoblasts into myotubes and the absence of this factor results in severe muscular deficiency. Using PCR primers designed from mammalian myogenin sequences, a 215 bp PCR product was amplified from porcine genomic DNA and found to be 89.7% homologous to mouse myogenin. A porcine cosmid library was screened with the myogenin PCR probe and a 6.5 kb portion of a cosmid containing the pig myogenin gene was sequenced. The sequence includes 5' flanking region, the entire protein coding region composed of three exons and two introns and 3' flanking region. The protein coding region was highly conserved (greater than or equal to 92.5%) with mouse and human myogenin coding regions. Transfection of pig myogenin into C3H10T1/2 cells, a multipotential fibroblast cell line, resulted in 28% myogenic conversion assayed by cell fusion to form multinucleated cells and synthesis of sarcomeric myosin. These results indicate that the cloned myogenin gene was capable of initiating myogenesis in a fibroblast cell line.