SOD1 and amyotrophic lateral sclerosis: With the exception of α6, the mRNAs encoding all α subunits has been reported in rat motoneurons [11], [12], [23], although the α4 subunit mRNA has been reported only in motoneurons of a transgenic mouse overexpressing a mutated variant of the gene coding for the superoxide dismutase 1, which is an animal model that clinically resemble amyotrophic lateral sclerosis (ALS) [13].