SOD1 and amyotrophic lateral sclerosis: Because denervation of fast-fatigable (FF) motor units in skeletal muscle precedes the spinal MN loss in patients with ALS and in SOD1, TDP-43 and FUS mouse models of ALS12,18,19, we next looked for evidence of denervation in the tibialis anterior (TA) muscle, which is innervated predominantly by FF MNs.