Intrinsic differences in MyoD and myogenin expression between primary cultures of SJL/J and BALB/C skeletal muscle.

The time course of expression of the skeletal muscle-specific regulatory genes MyoD and myogenin was studied in primary cultures of skeletal muscle from adult SJL/J and BALB/c mice. In situ detection of expression with MyoD and myogenin riboprobes and myogenin antibody showed that the onset of expression of these genes occurred earlier in cells from SJL/J mice. Probe-positive cells and myotubes were also more frequent in cultures from SJL/J mice than in BALB/c. The onset of expression of MyoD and myogenin was delayed in cultured cells relative to the time course seen following injury in vivo. Myogenin protein was demonstrated in replicating cells and all myogenin-positive cells expressed desmin. The observed strain-specific difference infers a greater intrinsic myogenicity of cells in SJL/J muscle in vitro and reflects the superior capacity for new muscle formation previously reported in SJL/J mice in vivo.