Based on the fact that the phenotype of these mice was improved by the CuII(atsm) treatment, despite an overall increase in levels of mutant SOD1, it was concluded that the metal state of the SOD1 is a greater determinant of the protein’s role in motor neuron death and the ALS-like phenotype of these animals than the mutant amino acid sequence per se. Here, SOD1 is linked to amyotrophic lateral sclerosis.