DMPK and myotonic dystrophy type 1: For example, the type 1 myotonic dystrophy (DM1) is caused by the expansion of the CTG trinucleotide repeat in the 3′ untranslated region (3′UTR) of DMPK gene (Meola and Cardani 2015; Sznajder and Swanson 2019; Yum et al. 2017).