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A novel GFP reporter mouse reveals M ustn1 expression in adult regenerating skeletal muscle, activated satellite cells and differentiating myoblasts
Author(s) -
Krause M. P.,
Moradi J.,
Coleman S. K.,
D'Souza D. M.,
Liu C.,
Kronenberg M. S.,
Rowe D. W.,
Hawke T. J.,
Hadjiargyrou M.
Publication year - 2013
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12099
Subject(s) - myod , myogenesis , cardiotoxin , myogenin , green fluorescent protein , desmin , skeletal muscle , biology , myocyte , microbiology and biotechnology , anatomy , immunology , immunohistochemistry , gene , genetics , vimentin
Aim Mustn1 has been implicated in myofusion as well as skeletal muscle growth and repair; however, the exact role and spatio‐temporal expression of M ustn1 have yet to be fully defined. Methods Transgenic mice were generated with a 1512‐bp sequence of the M ustn1 promoter directing the expression of GFP ( M ustn1 PRO ‐ GFP ). These mice were used to investigate the spatio‐temporal expression of M ustn1 PRO ‐ GFP during skeletal muscle development and adult skeletal muscle repair, as well as various phases of the satellite cell lifespan (i.e. quiescence, activation, proliferation, differentiation). Results Mustn1 PRO ‐ GFP expression was observed within somites at embryonic day 12 and developing skeletal muscles at embryonic day 15 and 18. While uninjured adult tibialis anterior muscle displayed no detectable M ustn1 PRO ‐ GFP expression, cardiotoxin injury robustly elevated M ustn1 PRO ‐ GFP expression at 3 days post‐injury with decreasing levels observed at 5 days and minimal, focal expression seen at 10 days. The expression of M ustn1 PRO ‐ GFP at 3 days post‐injury consistently overlaid with MyoD although the strongest expression of M ustn1 PRO ‐ GFP was noted in newly formed myotubes that were expressing minimal levels of MyoD. By 5 days post‐injury, M ustn1 PRO ‐ GFP overlaid in all myotubes expressing myogenin although cells were present expressing M ustn1 PRO ‐ GFP alone. The expression patterns of M ustn1 PRO ‐ GFP in regenerating muscle preceded the expression of desmin throughout the regenerative time course consistent with M ustn1 being upstream of this myogenic protein. Further, quiescent satellite cells located on freshly isolated, single myofibers rarely expressed M ustn1 PRO ‐ GFP , but within 24 h of isolation, all activated satellite cells expressed M ustn1 PRO ‐ GFP . Expression of M ustn1 PRO ‐ GFP in primary myoblasts diminished with prolonged time in proliferation media. However, in response to serum withdrawal, the expression of Mustn1 PRO ‐ GFP increased during myofusion (day 2) followed by declining expression thereafter. Conclusion Mustn1 PRO ‐ GFP is expressed in activated satellite cells and myoblasts but continued time in proliferation media diminished M ustn1 PRO ‐ GFP expression. However, myoblasts exposed to serum withdrawal increased M ustn1 PRO ‐ GFP expression consistent with its demonstrated role in myofusion. The in vivo expression pattern of M ustn1 observed in regenerating and developing skeletal muscle is consistent with its presence in satellite cells and its critical role in myofusion.