SOD1 and amyotrophic lateral sclerosis: The mechanism of generation of TDP-43 toxic fragments requires further study; however, we observed a direct interaction between mutant SOD1 and TDP-43 in an ALS cell line (Fig. 5b) and the spinal cord of the hSOD1G93A mice at 120 days of age (Fig. 2d) via co-immunoprecipitation.