SOD1 and amyotrophic lateral sclerosis: A mutation of the NFL gene in a genetic mouse model of ALS causes degeneration of spinal motor neurons with accumulation of neurofilaments and atrophy of skeletal muscle (Lee et al., 1994), while genetic deletion of the NFL subunit in the SOD1-mutant ALS mouse model slowed disease onset and progression, at the same time reducing selectivity of the disease process toward motor neurons (Williamson et al., 1998).