The receptor p75 has also been implicated in retrograde degenerative signaling in motor neurons of superoxide dismutase 1 mutant mice (SOD1G93A), which undergo axon degeneration and eventual motor neuron apoptosis and have been used as a model for amyotrophic lateral sclerosis (ALS) [76]. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.