Rest is required for the regenerative response of skeletal muscle

The Repressor Element 1 Silencing Transcription factor (REST) also known as Neuron Restrictive Silencing Factor (NRSF) is a primary regulator of neurogenesis, the process involved in the formation of new neuronal cells starting from neuronal stem cells (NCSs) or neuronal progenitor cells. REST acts as a transcriptional repressor of neuronal-specific genes in both neuronal and non-neuronal cells. Neuronal gene expression is restricted by the association of REST with two corepressor complexes, mSin3 and coREST which in turn recruit histone deacetylases (HDACs) to REST-associated genes’ promoters leading to a repression of gene expression. HDACs are involved in explicating a repressive activity within genes involved in myogenic differentiation and muscle regeneration into skeletal muscle tissue such as MyoD and MEF2 genes. In this work, we generated C57BL/6:RESTFlox/Flox/MyoDCre+/Cre+ and dystrophic mdx:RESTFlox/Flox/MyoDCre+/Cre+ murine knockout models to inhibit REST expression selectively in muscle tissue. We isolated satellite cells from newborn mice and we evaluated the proliferative and differentiation potential of the sorted cells. Satellite cells were characterized for the expression of myogenic markers like Pax7, Myf5, MyoD and Myogenin by Real-time PCR (qRT-PCR) analysis. We characterized the skeletal muscle tissues of normal and dystrophic wild-type and ko mice by Hematoxylin and Eosin (H&E), Azan Mallory, ATPase and SDH stainings. Myofiber Cross Sectional Area (CSA) was measured. To characterize the involvement of REST in the context of muscle regeneration, we evaluated the muscle regeneration process in damaged skeletal muscles in response to an injury induced by cardiotoxin (CTX). Data demonstrated that in TA muscle of mdx:mREST KO mice was still present muscle regeneration between 10 and 21 days suggesting a delay in muscle maturation after damage. We supposed that REST could be required for the regenerative response in the skeletal muscle tissue. In particular, REST could be involved in the formation of a regulator transcriptional complex able to influence and control myogenic differentiation and muscle regeneration. Future studies will be helpful to identify target genes and DNA binding-sites associated to REST activity in skeletal muscle tissue during muscle regeneration.