A novel GFP reporter mouse reveals Mustn1 expression in adult regenerating skeletal muscle, activated satellite cells and differentiating myoblasts. (15th April 2013)

• Record Type: Journal Article
• Authors: 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.
• Is Part Of: Acta physiologica. Volume 208:Number 2(2013:Jun.)
• Page Start: 180
• Page End: 190
• Publication Date: 2013-04-15
• Subjects: Physiology -- Periodicals; Physiology -- Research -- Periodicals; 612
• DOI: 10.1111/apha.12099
• Languages: English
• ISSNs: 1748-1708

Abstract

<abstract abstract-type="main" id="apha12099-abs-0001"> <title>Abstract</title> <sec id="apha12099-sec-0001" sec-type="section"> <title>Aim</title> <p> <italic>Mustn1</italic> has been implicated in myofusion as well as skeletal muscle growth and repair; however, the exact role and spatio‐temporal expression of <italic>Mustn1</italic> have yet to be fully defined.</p> </sec> <sec id="apha12099-sec-0002" sec-type="section"> <title>Methods</title> <p>Transgenic mice were generated with a 1512‐bp sequence of the <italic>Mustn1</italic> promoter directing the expression of GFP (<italic>Mustn1</italic><sup>PRO</sup>‐GFP). These mice were used to investigate the spatio‐temporal expression of <italic>Mustn1</italic><sup>PRO</sup>‐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).</p> </sec> <sec id="apha12099-sec-0003" sec-type="section"> <title>Results</title> <p> <italic>Mustn1</italic> <sup>PRO</sup>‐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 <italic>Mustn1</italic><sup>PRO</sup>‐GFP expression, cardiotoxin injury robustly elevated <italic>Mustn1</italic><sup>PRO</sup>‐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 <italic>Mustn1</italic><sup>PRO</sup>‐GFP at 3 days post‐injury consistently overlaid with MyoD although the strongest expression of <italic>Mustn1</italic><sup>PRO</sup>‐GFP was noted in newly formed myotubes that were expressing minimal levels of MyoD. By 5 days post‐injury, <italic>Mustn1</italic><sup>PRO</sup>‐GFP overlaid in all myotubes expressing myogenin although cells were present expressing <italic>Mustn1</italic><sup>PRO</sup>‐GFP alone. The expression patterns of <italic>Mustn1</italic><sup>PRO</sup>‐GFP in regenerating muscle preceded the expression of desmin throughout the regenerative time course consistent with Mustn1 being upstream of this myogenic protein. Further, quiescent satellite cells located on freshly isolated, single myofibers rarely expressed <italic>Mustn1</italic><sup>PRO</sup>‐GFP, but within 24 h of isolation, all activated satellite cells expressed <italic>Mustn1</italic><sup>PRO</sup>‐GFP. Expression of <italic>Mustn1</italic><sup>PRO</sup>‐GFP in primary myoblasts diminished with prolonged time in proliferation media. However, in response to serum withdrawal, the expression of <italic>Mustn1</italic><sup>PRO</sup>‐GFP increased during myofusion (day 2) followed by declining expression thereafter.</p> </sec> <sec id="apha12099-sec-0004" sec-type="section"> <title>Conclusion</title> <p> <italic>Mustn1</italic> <sup>PRO</sup>‐GFP is expressed in activated satellite cells and myoblasts but continued time in proliferation media diminished <italic>Mustn1</italic><sup>PRO</sup>‐GFP expression. However, myoblasts exposed to serum withdrawal increased <italic>Mustn1</italic><sup>PRO</sup>‐GFP expression consistent with its demonstrated role in myofusion. The <italic>in vivo</italic> expression pattern of <italic>Mustn1</italic> observed in regenerating and developing skeletal muscle is consistent with its presence in satellite cells and its critical role in myofusion.</p> </sec> </abstract>