The observations described here and in the previous study [29] confirm that the aberrant partitioning of MBNL family members is a persistent feature in clonally-derived cDM myoblasts with the (CTG)2600 repeat, in a manner like that seen in muscle and nerve cells from DM1 patients with long repeats [22,30]. This evidence concerns the gene MBNL1 and myotonic dystrophy type 1.