Bcl-2 expression identifies an early stage of myogenesis and promotes clonal expansion of muscle cells.
We show that Bcl-2 expression in skeletal muscle cells identifies an early stage of the myogenic pathway, inhibits apoptosis, and promotes clonal expansion. Bcl-2 expression was limited to a small proportion of the mononucleate cells in muscle cell cultures, ranging from approximately 1-4% of neonatal and adult mouse muscle cells to approximately 5-15% of the cells from the C2C12 muscle cell line. In rapidly growing cultures, some of the Bcl-2-positive cells coexpressed markers of early stages of myogenesis, including desmin, MyoD, and Myf-5. In contrast, Bcl-2 was not expressed in multinucleate myotubes or in those mononucleate myoblasts that expressed markers of middle or late stages of myogenesis, such as myogenin, muscle regulatory factor 4 (MRF4), and myosin. The small subset of Bcl-2-positive C2C12 cells appeared to resist staurosporine-induced apoptosis. Furthermore, though myogenic cells from genetically Bcl-2-null mice formed myotubes normally, the muscle colonies produced by cloned Bcl-2-null cells contained only about half as many cells as the colonies produced by cells from wild-type mice. This result suggests that, during clonal expansion from a muscle progenitor cell, the number of progeny obtained is greater when Bcl-2 is expressed.
Myogenesis Research Laboratory, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
J A
JA
Dominov
J J
JJ
Dunn
J B
JB
Miller
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins; D003893:Desmin / Q000235:genetics; D015870:Gene Expression; D019254:Genes, bcl-2; D005819:Genetic Markers; D051379:Mice; D018345:Mice, Knockout; D024510:Muscle Development; D009124:Muscle Proteins / Q000235:genetics; D018482:Muscle, Skeletal / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D017570:MyoD Protein / Q000235:genetics; D051787:Myogenic Regulatory Factor 5; D016133:Polymerase Chain Reaction; D019311:Staurosporine / Q000494:pharmacology; D015534:Trans-Activators
D017931:DNA Primers; D004268:DNA-Binding Proteins; D003893:Desmin; D005819:Genetic Markers; D009124:Muscle Proteins; C497418:Myf5 protein, mouse; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D015534:Trans-Activators; D019311:Staurosporine