Transcriptomic analysis of total plantaris muscles RNA extract before and after one week of overload

Adult skeletal muscle is a plastic tissue that can adapt its size to workload. Here, we show that RhoA within myofibers is needed for overload-induced hypertrophy by controlling satellite cell fusion to the growing myofibers without affecting protein synthesis. At the molecular level, we demonstrate that, in response to increased workload, RhoA controls in a cell autonomous manner Erk1/2 activation and the expressions of extracellular matrix (ECM) regulators such as Mmp9/Mmp13/Adam8 and of macrophage chemo-attractants such as Ccl3/Cx3cl1. Their decreased expression in RhoA mutant is associated with ECM and fibrillar collagen disorganization and lower macrophage infiltration. Moreover, Mmps inhibition and macrophage depletion in controls phenocopied the lack of growth of RhoA mutants. These findings unravel the implication of RhoA within myofibers, in response to increase load, in the building of a permissive microenvironment for muscle growth and for satellite cell accretion through ECM remodeling and inflammatory cell recruitment. The aim of the analysis is to compare plantaris muscle controls and plantaris muscles mutants lacking RhoA (RhoA loss occurs in the myofibers) before and after compensatory hypertrophy induction. RhoA deletion occurs in vivo, in adult myofibers once that the mice were injected with tamoxifen. The mice were submitted to overload procedure (cut of gastrocnemius and soleus tendons in order to achieve plantaris muscle hypertrophy). One week after surgery mice were sacrificed and plantaris muscles were collected. Sham operated mice, control and mutant, were used as controls. RNA was isolated by plantaris muscles using TRIzol™ protocol. Microarray analysis will help to understand the molecular pathways involved in muscle growth defect observed in absence of RhoA upon hypertrophy. Isolated RNA from 4 mutant sham operated muscles, 4 mutant overloaded muscles, 3 controls sham operated muscles and 4 controls overloaded muscles were used to perform trasncriptomic arrays.