An Overview of Circular RNAs and Their Implications in Myotonic Dystrophy

Circular RNAs (circRNAs) are a class of single-stranded covalently closed RNA rings. Biogenesis of circRNAs, which may occur co-transcriptionally and post-transcriptionally via a back-splicing mechanism, requires the presence of complementary and/or inverted repeat sequences in introns flanking back-spliced exons and is facilitated by RNA-binding proteins. CircRNAs are abundant across eukaryotes; however, their biological functions remain largely speculative. Recently, they have been emerging as new members of a gene regulatory network and contributing factors in various human diseases including cancer, neurological, muscular and cardiovascular disorders. In this review, we present an overview of the current knowledge about circRNAs biogenesis and their aberrant expression in various human disorders. In particular, we focus on the latest discovery of circRNAs global upregulation in myotonic dystrophy type 1 (DM1) skeletal muscles and the role these prospective biomarkers might have for prognosis and therapeutic response in DM1.