Altered expression of myosin mRNA and protein in rat soleus and tibialis anterior following reinnervation.
Myosin heavy chain (MHC) expression was studied in rat soleus and tibialis anterior (TA) at the mRNA and protein levels following reinnervation 8 and 32 wk after sciatic nerve injury. A sciatic nerve crush or transection injury was produced in the midthigh region of adult female Sprague-Dawley rats. A ribonuclease protection assay was developed to measure four of the adult MHCs (I, IIa, IIx, IIb) in a single sample. MHC mRNA and protein were measured and compared in the same muscles. Eight and thirty-two weeks after a crush injury, the MHC mRNA profiles were similar to control with the exception of soleus MHC IIa and TA MHC IIb, which were significantly less than control at both time points. In contrast, reinnervation of the soleus following a sciatic nerve transection injury resulted in an MHC isoform shift characterized by increases in the relative amounts of fast myosin (IIa and IIx) and a decrease in slow myosin. As expected, significant changes first occurred at the mRNA level followed by changes in protein expression. Thirty-two weeks after transection injury and repair, the primary MHC mRNA isoform in the soleus was MHC IIx. Moreover, at 32 wk, MHC IIb mRNA was detected in 50% of the reinnervated soleus following a transection injury. Reinnervation of the TA following sciatic nerve transection led to replacement of the MHC IIb isoform with MHC IIx.
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Biomedical Sciences Program, University of California, San Diego, School of Medicine, USA.
Bodine
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D000595:Amino Acid Sequence; D000818:Animals; D003714:Denervation; D005260:Female; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D018995:Myosin Heavy Chains / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology; D016415:Sequence Alignment
D012333:RNA, Messenger; D018995:Myosin Heavy Chains