As well as raised levels of mutant SOD1 affecting phenotype, increased levels of WT SOD1 also give rise to neurodegeneration—overexpression of WT human SOD1 at levels comparable with that found in SOD1G93A transgenics results in an ALS-like syndrome with progressive loss of spinal motor neurons and premature death (19). Here, SOD1 is linked to amyotrophic lateral sclerosis.