S. macrurus myogenic regulatory factors (MRFs) induce mammalian skeletal muscle differentiation; evidence for functional conservation of MRFs.
The current-producing cells of the electric organ, i.e., electrocytes, in Sternopygus macrurus derive from skeletal muscle fibers. Mature electrocytes are not contractile, but they do retain some muscle proteins, are multinucleated, and receive cholinergic innervation. Electrocytes express the myogenic regulatory factors (MRFs) MyoD, myogenin, Myf5 and MRF4 despite their incomplete muscle phenotype. Although S. macrurus MRFs share functional domains which are highly conserved and their expression is confined to the myogenic lineage, their capability to induce the muscle phenotype has not been determined. To test the functional conservation of S. macrurus MRFs to transcriptionally activate skeletal muscle gene expression and induce the myogenic program, we transiently over-expressed S. macrurus MyoD (SmMyoD) and myogenin (SmMyoG) in mouse C3H/10T1/2 and NIH3T3 embryonic cells. RT-PCR and immunolabeling studies showed that SmMyoD and SmMyoG can efficiently convert these two cell lines into multinucleated myotubes which expressed differentiated muscle markers. The levels of myogenic induction by SmMyoD and SmMyoG were comparable to those obtained with mouse MRF homologs. Furthermore, SmMyoD and SmMyoG proteins were able to induce mouse MyoD and myogenin in C3H/10T1/2 cells. We conclude that S. macrurus MRFs are functionally conserved as they can transcriptionally activate skeletal muscle gene expression and induce the myogenic program in mammalian non-muscle cells. Hence, these data suggest that the partial muscle phenotype of electrocytes is not likely due to differences in the MRF-dependent transcriptional program between skeletal muscle and electric organ.
Kim
Hyun-Jung
HJ
Department of Biology, New Mexico State University, Las Cruces, 88003, USA.
Güth
Robert
R
Jonsson
Colleen B
CB
Unguez
Graciela A
GA
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004557:Electric Organ / Q000166:cytology / Q000378:metabolism; D023702:Gymnotiformes / Q000235:genetics; D051379:Mice; D024510:Muscle Development / Q000235:genetics / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism*; D017570:MyoD Protein / Q000235:genetics / Q000502:physiology; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000502:physiology*; D018008:Myogenin / Q000235:genetics / Q000502:physiology; D041681:NIH 3T3 Cells; D010641:Phenotype; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D015533:Transcriptional Activation; D014162:Transfection
D017931:DNA Primers; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D011994:Recombinant Proteins