Analysis of altered gene expression in rat soleus muscle atrophied by disuse

The present study involved a global analysis of genes whose expression was modified in rat soleus muscle atrophied after hindlimb suspension (HS). HS muscle unloading is a common model for muscle disuse that especially affect s antigravity slow-twitch muscles such as the soleus muscle. A cDNA cloning Strategy, based on suppression subtractive hybridization technology, led t o the construction of two normalized soleus muscle cDNA libraries that were subtracted in opposite directions, i.e., atrophied soleus muscle cDNAs sub tracted by control cDNAs and vice versa. Differential screening of the two libraries revealed 34 genes with altered expression in HS soleus muscle, in cluding 11 novel cDNAs, in addition to the 2X and 2B myosin heavy chain gen es expressed only in soleus muscles after HS. Gene up- and down-regulations were quantified by reverse Northern blot and classical Northern blot analy sis. The 25 genes with known functions fell into seven important functional categories. The homogeneity of gene alterations within each category gave several clues for unraveling the interplay of cellular events implied in th e muscle atrophy phenotype. In particular, our results indicate that modula tions in slow- and fast-twitch-muscle component balance, the protein synthe sis/secretion pathway, and the extracellular matrix/cytoskeleton axis are l ikely to be key molecular mechanisms of muscle atrophy. In addition, the cl oning of novel cDNAs underlined the efficiency of the chosen technical appr oach and gave novel possibilities to further decipher the molecular mechani sms of muscle atrophy. J. Cell. Biochem. 83: 508-519, 2001. (C) 2001 Wiley- Liss, Inc.