These findings led to the concept of ALS as a “dying back” disorder in which muscle denervation precedes the death of the motor neuron cell body, and suggests that SOD1 gain of function can also lead to NMJ degeneration—and potentially also contributing to the distal neuropathy seen in Sod1D83G/D83G mice. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.