Gain of RNA function in pathological cases: Focus on myotonic dystrophy

► RNA gain-of-function emerged as a new mechanism for diseases with expanded repeats. ► Myotonic dystrophy type 1 is a dominant inherited disease caused by an CTG expansion. ► The expanded CTG repeat is located in the 3′ non-coding region of the DMPK gene. ► This review focused on toxic RNA gain-of-function as a pathogenic mechanism for DM1. ► DM1 neuromuscular disease belongs to the new family of RNA-dominant disorders.