SOD1 and amyotrophic lateral sclerosis: Since the development of transgenic mice expressing human SOD1 containing ALS-causing substitution mutations3, 4, these mouse models have provided a robust experimental approach to study ALS pathogenesis and progression, as well as opportunity to test new therapeutics in a system that entails basic yet clinically significant features (e.g. a mammalian blood-brain barrier and an adult-onset progressive phenotype).