Plasticity of mammalian myotubes upon stimulation with a thrombin-activated serum factor.

Salamanders display unique regeneration abilities among adult vertebrates. An intriguing feature of salamander regeneration is the dedifferentiation of cells, such as myofibers and myotubes at the injury site, a process that involves cell cycle re-entry from the differentiated state. A thrombin-activated serum factor that is distinct from conventional growth factors is known to cause S-phase re-entry in salamander myotubes. While mammalian myotubes do not re-enter S-phase upon serum stimulation, an upregulation of some immediate early genes such as jun and fos has been observed. Until now, it was unknown whether this transcriptional response was stimulated by conventional growth factors or by the thrombin-activated serum factor. By measuring transcriptional activity in individually purified C2C12 mouse myotubes using quantitative reverse transcription polymerase chain reactions, we show that a set of immediate early genes are activated in response to the thrombin-activated serum factor in a distinct manne...