Evaluation of Muscle miRNA as Biomarkers in Dystrophinopathies

Duchenne muscular dystrophy (DMD) , caused by mutations in the DMD gene, is the most common and most severe progressive dystrophy of the child. Although the development is rapidly progressive , there is variability in the severity of the disease between DMD patients that do not correlate with the type of mutations in the DMD gene. There are no easily measurable biomarkers for monitoring the DMD or moderate form of the disease, Becker muscular dystrophy (BMD ) . MicroRNAs (miRNAs) are involved in most cellular processes , and their expression pattern is a signature of the state of a cell . They represent a potential class of diagnostic and prognostic biomarkers. Some are specific for the skeletal myogenesis , and changes in their pattern of expression are associated with muscle diseases including muscular dystrophy. The levels of muscle- specific miRNAs are indeed greatly increased in the serum of DMD and BMD compared to control patients . The main objective of this is to validate the use of serum muscle-derived microRNAs as biomarkers of DMD patients (compared with healthy subjects). Secondary objectives are i) to investigate the relationship between circulating levels of these miRNAs and the severity of the dystrophinopathy (DMD vs BMD) and also the progression of the disease (longitudinal study), ii) to assess the specificity of these markers for dystrophinopathy (comparison with other patients with muscular dystrophy), iii) to test candidate miRNAs recently identified but not yet analyzed in the serum of patients. Clinical data and samples will be recorded at each regular consultation. miRNA levels will be quantified using Real Time Quantitative RT-PCR.