Similar to that of axonal pathology found in Optn -/- mice,6 another ALS model, the axonal pathology of SOD1G93A mice is manifested as a decompaction of myelin sheaths with a decreased g-ratio and an increased number of large-diameter axons, suggesting degeneration and swelling of motor neuron axons (Fig. 2a, b). Here, OPTN is linked to amyotrophic lateral sclerosis.