Overall Kif1bα/KIF1Bα levels relative to total Kif1b/KIF1B are decreased in mouse embryonic fibroblasts lacking Mbnl1 and Mbnl2 (DKO), and in human DM1 tibialis anterior biopsies (Fig. 7b, c). This evidence concerns the gene MBNL2 and myotonic dystrophy type 1.