SOD1 and amyotrophic lateral sclerosis: Wong and Martin (2010) demonstrated that expression of mutant human SOD1 (hSOD1) in the skeletal muscles causes motor neuron degeneration in an ALS animal model and suggested that the muscles could be the primary site for pathogenesis in ALS. Boillee et al. (2006) showed that microglia and astrocytes contribute to the degeneration of motor neurons, leading to disease pathogenesis.