The expression profile of myogenic transcription factors in satellite cells from denervated rat muscle.

Abstract

The muscle-specific transcription factors of the MyoD family are altered after denervation. In order to determine whether this shift takes place in satellite cells (SC), we investigated the expression pattern of MyoD, myf5, myogenin, and MRF4 in SC. Hindlimb muscles of rats were denervated for 2 days to 4 weeks. SC were isolated, pooled and the transcription of all 4 factors was assessed by RT-PCR. Protein expression was assessed in histological sections of soleus and anterior tibial (TA) muscles; SC were identified by M-cadherin. Pooled SC from innervated muscles expressed myf5 mRNA, and very weakly MyoD and myogenin mRNA. MyoD and myogenin protein was found in only few SC. After denervation, pooled SC expressed myf5 mRNA, and very weakly myogenin and MRF4 mRNA. Myogenin protein was found in less than about 10% of the cells, whereas MRF4 protein was absent from SC. We conclude that the presence of myf5 and the absence of MyoD and MRF4 protein in SC after denervation indicated the quiescent state of the cell cycle. A subset of SC has additionally acquired myogenin. SC after denervation might be less easily recruited into the mitotic cycle than SC from normal muscle, rendering regeneration of denervated muscle less efficient than normal muscle.