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. The gene discussed is TARDBP; the disease is amyotrophic lateral sclerosis.