LOCALIZATION OF MYF-5, MRF4 AND ALPHA-CARDIAC ACTIN MESSENGER-RNAS INREGENERATING XENOPUS SKELETAL-MUSCLE

We have analysed the spatial and temporal expression patterns of Myf-5 , MRF4 and alpha cardiac actin mRNAs during muscle regeneration follow ing cardiotoxin injury in adult Xenopus laevis using in situ hybridiza tion. Myf-5 transcripts began to be detected in the activated satellit e cells as early as the beginning of the regeneration process, then dr amatically decreased in young plurinucleated myotubes. MRF4 mRNA was d etected later, just before the young myotube stage, and was strongly e xpressed during the different stages of the maturation myotubes. Like Myf-5, alpha cardiac actin mRNA began to accumulate early in activated satellite cells. These results, which contribute to an overview of th e expression of the genes coding for myogenic bHLH proteins during mus cle regeneration, are discussed in relation to the expression of these factors during development. ((C) Academie des sciences/Elsevier, Pari s).