Calcium is a universal second messenger regulating different biological functions from muscle contraction and neuronal excitability, to gene transcription and cell death. Physiologically, Ca2+ signals result both from the release of Ca2+ from intracellular stores (endo/sarcoplasmic reticulum) as well as influx from the extracellular environment, via the opening of channels on the plasma membrane. The Ca2+ that is stored in the endoplasmic/sarcoplasmic reticulum is released into the cytoplasm via the opening of intracellular calcium channels belonging to the inositol trisphosphate receptor and ryanodine receptor family.Type 1 ryanodine receptor (RyR1) is the channel responsible for releasing Ca2+ from skeletal muscle sarcoplasmic reticulum after plasma membrane depolarization. RyR1plays a fundamental role in muscle physiology as illustrated by the fact that ryr1-/- mice die immediately after birth and that in humans, mutations in RYR1, the gene encoding the RyR1, lead to several neuromuscular disorders including Malignant Hyperthermia, Core myopathies, Centronuclear myopathy, Congenital Fiber Type Dysproportion and exertional heat stroke. The disease phenotype resulting from RYR1 mutations largely depends on their location within the RYR1 coding sequence and whether the mutations are dominant or recessive. Dominant mutations are more commonly associated with the Malignant Hyperthermia Susceptibility/exertional rhabdomyolysis and Central Core Disease phenotypes, while most cases of Multiminicore Disease, Centronuclear myopathy and Congenital Fiber Type Dysproportion phenotypes are associated with recessive mutations. From a general point of view, dominant RYR1 mutations affect the biophysical properties of the Ca2+ channel, while recessive mutations have a more modest effect on the biophysical properties of the Ca2+ channel, and their precise mode of action has not been investigated in detail. A consistent finding in muscle biopsies of patients with autosomal recessive RYR1 myopathies is the significant decrease of RyR1 protein; a decrease in sarcoplasmic reticulum Ca2+ channels would be associated with less Ca2+ release leading to less efficient muscle contraction and weaker muscles. In the past few years our research has focused on understanding the mechanisms responsible for the drastic decrease in RyR1 content. Our results have shown that profound epigenetic modifications occur in muscles of patients with recessive RYR1 mutations, including RYR1 CpG island hyper-methylation, decrease in muscle-specific microRNA content and abnormal expression of class II histone deacetylases. Interestingly, a decrease in RyR1 protein in the muscles of patients with congenital myopathies caused by mutations in other genes including MTM1, SELENON, NEB hve also been observed, indicating that a common pathomechanism of disease, consequent to the primary genetic mutation, may exist.The aim of this project is to gain insight into the mechanisms causing the epigenetic modifications and validate whether they represent valid pharmacological targets. In order to do this we will use a knock in animal model we have generated, carrying two RYR1 mutations that were identified in a severely affected patient (namely RYR1 p.Q1970fx/p.A4329D). We will examine whether (i) skeletal muscles from the mouse model exhibit similar pathophysiological and epigenetic changes as those reported in human patients and (ii) investigate whether class II HDAC and DNA methyltransferase inhibitors constitute suitable pharmacological agents to improve the muscle function of the RYR1 mutant mouse model. Additionally we will investigate the muscles of human patients with congenital myopathies that share as a common feature reduced RyR1 protein content, in order to verify whether common molecular signatures caused by the altered activity of enzymes involved in chromatin modification (HDACs and DNA methylating enzymes) occur. We think that discovering a common pharmacological target downstream the primary genetic defect could potentially benefit a large number of patients with congenital myopathies of diverse genetic causes.