A previous study using motor neurons differentiated from DM1 embryonic stem cells also demonstrated abundant neuritogenesis associated with a marked impairment in the formation of neuromuscular connections.67 Because reduced axon branching is associated with abnormal neuromuscular junction formation,68 our results suggest the possibility that the aberrant splicing of CAMKK2 in DM1 affects the morphology of motor neurons by altering the balance between neurite branching and elongation, although how the decreased axon branching induces DM1 pathology remains unclear. This evidence concerns the gene CAMKK2 and myotonic dystrophy type 1.