Characterization of muscle-specific expression of miRNAs in duchenne muscular dystrophy

The miRNAs are a class of highly-conserved and tissue-specific non-coding RNAs involved in post transcriptional regulation. Animal miRNAs typically form imperfectly base-pair duplexes with microRNA response element (MRE) in target mRNAs and this interaction inhibits translation of the target mRNA. In this study, we wanted to clarify the role of muscle-specific miRNAs in the pathogenesis of Duchenne muscular dystrophy (DMD). DMD is a muscle degenerative disease caused by a mutation in the gene encoding dystrophin. The molecular mechanisms responsible for the pathogenesis are not completely clear but recent reports demonstrated an involvement of some miRNAs in muscle development. Three miRNAs (miR-1, miR-133 and miR-206) are muscle-specific and seem to be involved in muscle proliferation and/or differentiation: they are all switched on during in vitro induced maturation of myoblast to myotube. More specifically it has been demonstrated that miR-1 induces muscle proliferation through inhibition of histone deacetylase 4 (HDAC4); miR-133 induces muscle differentiation through inhibition of serum response factor (SRF) and miR-206 induces muscle differentiation through the inhibition of three different target, Utrophyn (Utr), the largest subunit of Dna Pol alpha (Pola1) and Connexin 43 (Cx43). Northern blot with DIG-labelled probes and real-time PCR were used to evaluate the presence and the level of expression of miR-1, miR-133 and miR-206 in human fetal and adult muscle obtained from normal and DMD subjects. We characterized the differences between adult and fetal tissues inside the same clinical group, to see if the pattern of miRNA expression is time-dependent, and between normal and DMD tissues, in order to understand the involvement of these miRNAs in the disease. Preliminary results indicate different expression of miRNA between normal and DMD subjects. These data suggest a possible miRNA implications in the muscle damage of Duchenne muscular dystrophy.