Limits...
Reduced differentiation potential of primary MyoD-/- myogenic cells derived from adult skeletal muscle.

Sabourin LA, Girgis-Gabardo A, Seale P, Asakura A, Rudnicki MA - J. Cell Biol. (1999)

Bottom Line: However, MyoD-/- myogenic cells did not express desmin, an intermediate filament protein typically expressed in cultured myoblasts in vitro and myogenic precursor cells in vivo.Under conditions that normally induce differentiation, MyoD-/- cells continued to proliferate and with delayed kinetics yielded reduced numbers of predominantly mononuclear myocytes.Expression of M-cadherin mRNA was severely decreased whereas expression of IGF-1 was markedly increased in MyoD-/- myogenic cells.

View Article: PubMed Central - PubMed

Affiliation: Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.

ABSTRACT
To gain insight into the regeneration deficit of MyoD-/- muscle, we investigated the growth and differentiation of cultured MyoD-/- myogenic cells. Primary MyoD-/- myogenic cells exhibited a stellate morphology distinct from the compact morphology of wild-type myoblasts, and expressed c-met, a receptor tyrosine kinase expressed in satellite cells. However, MyoD-/- myogenic cells did not express desmin, an intermediate filament protein typically expressed in cultured myoblasts in vitro and myogenic precursor cells in vivo. Northern analysis indicated that proliferating MyoD-/- myogenic cells expressed fourfold higher levels of Myf-5 and sixfold higher levels of PEA3, an ETS-domain transcription factor expressed in newly activated satellite cells. Under conditions that normally induce differentiation, MyoD-/- cells continued to proliferate and with delayed kinetics yielded reduced numbers of predominantly mononuclear myocytes. Northern analysis revealed delayed induction of myogenin, MRF4, and other differentiation-specific markers although p21 was upregulated normally. Expression of M-cadherin mRNA was severely decreased whereas expression of IGF-1 was markedly increased in MyoD-/- myogenic cells. Mixing of lacZ-labeled MyoD-/- cells and wild-type myoblasts revealed a strict autonomy in differentiation potential. Transfection of a MyoD-expression cassette restored cytomorphology and rescued the differentiation deficit. We interpret these data to suggest that MyoD-/- myogenic cells represent an intermediate stage between a quiescent satellite cell and a myogenic precursor cell.

Show MeSH

Related in: MedlinePlus

Role of MyoD in regulating satellite cell function.  RT-PCR analysis of single cells on cultured myofibers reveals  quiescent satellite cells express c-met but no detectable MRFs.  Activated satellite cells first express Myf-5 or MyoD before coexpressing both Myf-5 and MyoD, and progressing through their  normal developmental program leading to terminal differentiation (Cornelison and Wold, 1997). In the absence of MyoD, satellite cells appear to exhibit a propensity for self-renewal rather  than progression through the differentiation program (Megeney  et al., 1996). Therefore, expression of Myf-5 alone may allow self-renewal of satellite cells either before returning to quiescence  (yellow arrows) or upregulating MyoD and formation of proliferative myogenic precursor cells (mpc) (white arrows). The potential and replicative capacity of cells expressing MyoD alone is unknown; however, these cells likely irreversibly progress through  the myogenic program. Taken together, we interpret these data  to suggest that MyoD−/− myogenic cells represent an intermediate stage between myogenic stem cell and a myogenic precursor  cell.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132931&req=5

Figure 9: Role of MyoD in regulating satellite cell function. RT-PCR analysis of single cells on cultured myofibers reveals quiescent satellite cells express c-met but no detectable MRFs. Activated satellite cells first express Myf-5 or MyoD before coexpressing both Myf-5 and MyoD, and progressing through their normal developmental program leading to terminal differentiation (Cornelison and Wold, 1997). In the absence of MyoD, satellite cells appear to exhibit a propensity for self-renewal rather than progression through the differentiation program (Megeney et al., 1996). Therefore, expression of Myf-5 alone may allow self-renewal of satellite cells either before returning to quiescence (yellow arrows) or upregulating MyoD and formation of proliferative myogenic precursor cells (mpc) (white arrows). The potential and replicative capacity of cells expressing MyoD alone is unknown; however, these cells likely irreversibly progress through the myogenic program. Taken together, we interpret these data to suggest that MyoD−/− myogenic cells represent an intermediate stage between myogenic stem cell and a myogenic precursor cell.

Mentions: The muscle regeneration deficit in MyoD−/− muscle suggests that expression of MyoD is required for satellite cells to efficiently form differentiation-competent myogenic precursor cells (Megeney et al., 1996). RT-PCR analysis reveals that activated satellite cells first express either Myf-5 alone or MyoD alone, before coexpressing Myf-5 and MyoD, and subsequently progressing through the myogenic program (Cornelison and Wold, 1997). Our analysis of the phenotype of primary MyoD−/− myogenic cells can be interpreted to suggest that MyoD−/− myogenic cells represent an intermediate stage between a quiescent satellite cell and a myogenic precursor cell. Together, these data suggest the hypothesis that expression of Myf-5 alone may define an intermediate developmental stage that provides a mechanism for satellite cell self-renewal. In this model, activated satellite cells expressing only Myf-5 could undergo cell division and either return to quiescence by downregulating Myf-5, or alternatively upregulating MyoD and progressing through the myogenic program (see Fig. 9). Clearly, further analysis of the developmental potential and phenotype of primary MyoD−/− myogenic cells may present a unique opportunity to investigate the early myogenic program of satellite cells.


Reduced differentiation potential of primary MyoD-/- myogenic cells derived from adult skeletal muscle.

Sabourin LA, Girgis-Gabardo A, Seale P, Asakura A, Rudnicki MA - J. Cell Biol. (1999)

Role of MyoD in regulating satellite cell function.  RT-PCR analysis of single cells on cultured myofibers reveals  quiescent satellite cells express c-met but no detectable MRFs.  Activated satellite cells first express Myf-5 or MyoD before coexpressing both Myf-5 and MyoD, and progressing through their  normal developmental program leading to terminal differentiation (Cornelison and Wold, 1997). In the absence of MyoD, satellite cells appear to exhibit a propensity for self-renewal rather  than progression through the differentiation program (Megeney  et al., 1996). Therefore, expression of Myf-5 alone may allow self-renewal of satellite cells either before returning to quiescence  (yellow arrows) or upregulating MyoD and formation of proliferative myogenic precursor cells (mpc) (white arrows). The potential and replicative capacity of cells expressing MyoD alone is unknown; however, these cells likely irreversibly progress through  the myogenic program. Taken together, we interpret these data  to suggest that MyoD−/− myogenic cells represent an intermediate stage between myogenic stem cell and a myogenic precursor  cell.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132931&req=5

Figure 9: Role of MyoD in regulating satellite cell function. RT-PCR analysis of single cells on cultured myofibers reveals quiescent satellite cells express c-met but no detectable MRFs. Activated satellite cells first express Myf-5 or MyoD before coexpressing both Myf-5 and MyoD, and progressing through their normal developmental program leading to terminal differentiation (Cornelison and Wold, 1997). In the absence of MyoD, satellite cells appear to exhibit a propensity for self-renewal rather than progression through the differentiation program (Megeney et al., 1996). Therefore, expression of Myf-5 alone may allow self-renewal of satellite cells either before returning to quiescence (yellow arrows) or upregulating MyoD and formation of proliferative myogenic precursor cells (mpc) (white arrows). The potential and replicative capacity of cells expressing MyoD alone is unknown; however, these cells likely irreversibly progress through the myogenic program. Taken together, we interpret these data to suggest that MyoD−/− myogenic cells represent an intermediate stage between myogenic stem cell and a myogenic precursor cell.
Mentions: The muscle regeneration deficit in MyoD−/− muscle suggests that expression of MyoD is required for satellite cells to efficiently form differentiation-competent myogenic precursor cells (Megeney et al., 1996). RT-PCR analysis reveals that activated satellite cells first express either Myf-5 alone or MyoD alone, before coexpressing Myf-5 and MyoD, and subsequently progressing through the myogenic program (Cornelison and Wold, 1997). Our analysis of the phenotype of primary MyoD−/− myogenic cells can be interpreted to suggest that MyoD−/− myogenic cells represent an intermediate stage between a quiescent satellite cell and a myogenic precursor cell. Together, these data suggest the hypothesis that expression of Myf-5 alone may define an intermediate developmental stage that provides a mechanism for satellite cell self-renewal. In this model, activated satellite cells expressing only Myf-5 could undergo cell division and either return to quiescence by downregulating Myf-5, or alternatively upregulating MyoD and progressing through the myogenic program (see Fig. 9). Clearly, further analysis of the developmental potential and phenotype of primary MyoD−/− myogenic cells may present a unique opportunity to investigate the early myogenic program of satellite cells.

Bottom Line: However, MyoD-/- myogenic cells did not express desmin, an intermediate filament protein typically expressed in cultured myoblasts in vitro and myogenic precursor cells in vivo.Under conditions that normally induce differentiation, MyoD-/- cells continued to proliferate and with delayed kinetics yielded reduced numbers of predominantly mononuclear myocytes.Expression of M-cadherin mRNA was severely decreased whereas expression of IGF-1 was markedly increased in MyoD-/- myogenic cells.

View Article: PubMed Central - PubMed

Affiliation: Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.

ABSTRACT
To gain insight into the regeneration deficit of MyoD-/- muscle, we investigated the growth and differentiation of cultured MyoD-/- myogenic cells. Primary MyoD-/- myogenic cells exhibited a stellate morphology distinct from the compact morphology of wild-type myoblasts, and expressed c-met, a receptor tyrosine kinase expressed in satellite cells. However, MyoD-/- myogenic cells did not express desmin, an intermediate filament protein typically expressed in cultured myoblasts in vitro and myogenic precursor cells in vivo. Northern analysis indicated that proliferating MyoD-/- myogenic cells expressed fourfold higher levels of Myf-5 and sixfold higher levels of PEA3, an ETS-domain transcription factor expressed in newly activated satellite cells. Under conditions that normally induce differentiation, MyoD-/- cells continued to proliferate and with delayed kinetics yielded reduced numbers of predominantly mononuclear myocytes. Northern analysis revealed delayed induction of myogenin, MRF4, and other differentiation-specific markers although p21 was upregulated normally. Expression of M-cadherin mRNA was severely decreased whereas expression of IGF-1 was markedly increased in MyoD-/- myogenic cells. Mixing of lacZ-labeled MyoD-/- cells and wild-type myoblasts revealed a strict autonomy in differentiation potential. Transfection of a MyoD-expression cassette restored cytomorphology and rescued the differentiation deficit. We interpret these data to suggest that MyoD-/- myogenic cells represent an intermediate stage between a quiescent satellite cell and a myogenic precursor cell.

Show MeSH
Related in: MedlinePlus