Additional evidence of the intrinsic role of SMN in SMA myopathy comes from the observation that depletion of SMN in type I SMA patients induces sarcomeric disarray not only in atrophic denervated skeletal myofibers (hereafter referred to as myofibers) but also in innervated hypertrophied ones [33]. Here, SMN1 is linked to proximal spinal muscular atrophy.