NKX6-1 and amyotrophic lateral sclerosis: The percentage of spinal motor neurons based on SMI32 (NEFH)- and NKX6.1-positive cells was also not statistically different between CTR and C9-ALS cultures—SMI32 (CTR = 59.7% and C9-ALS = 43.5%) and NKX6.1 (CTR = 39.3% and C9-ALS = 27.1%).