Reversibility of muscle differentiation in the absence of commitment: analysis of a myogenic cell line temperature-sensitive for commitment.
The interrelationship between commitment (irreversible withdrawal from the cell cycle) and muscle-specific gene expression was analyzed with the myogenic cell line ts 3b-2, which is temperature sensitive for commitment and cell fusion. The rates of synthesis and levels of accumulation of muscle-specific mRNAs and proteins in the ts 3b-2 cells at permissive and nonpermissive temperatures are comparable, indicating that neither commitment nor cell fusion is required for induction of muscle-specific gene expression. In the absence of commitment, the cells are reversibly withdrawn from the cell cycle during gene induction, and expression of the muscle-specific genes is deinduced upon the switch to growth-stimulating conditions. The deinduction reflects coordinate and preferential cessation of muscle-specific mRNA synthesis, coupled with destabilization of the muscle-specific mRNAs in the cytoplasm, without effect on constitutively expressed housekeeping protein genes. The phenotype of the ts 3b-2 cells demonstrates that commitment and muscle-specific gene expression are both required, but alone are insufficient, to produce the terminally differentiated muscle phenotype.
D000199:Actins / Q000096:biosynthesis; D000818:Animals; D002453:Cell Cycle; D002454:Cell Differentiation; D002459:Cell Fusion; D002460:Cell Line; D003599:Cytoskeleton / Q000648:ultrastructure; D005786:Gene Expression Regulation; D051379:Mice; D009124:Muscle Proteins / Q000096:biosynthesis / Q000235:genetics*; D009132:Muscles / Q000166:cytology* / Q000378:metabolism; D009218:Myosins / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D013696:Temperature; D015533:Transcriptional Activation; D014336:Troponin / Q000096:biosynthesis; D020107:Troponin T
D000199:Actins; D009124:Muscle Proteins; D012333:RNA, Messenger; D014336:Troponin; D020107:Troponin T; D009218:Myosins