DMPK and myotonic dystrophy type 1: In DM1, CTG microsatellite repeat expansion in the 3’ untranslated region of dystrophia myotonica protein kinase (DMPK) gene induces the expression of toxic RNA aggregates (nuclear foci), which is thought to cause aberrant splicing of various genes, leading to multisystemic symptoms in various tissues, including heterogeneous brain involvement [199, 200].