OLIG2 and amyotrophic lateral sclerosis: However, we observed axonopathy including axonal swelling and subsequent degeneration of axons, which are the characteristic phenotypes of motor axons in ALS (Laird et al. 2008; King et al. 2011; Kobayakawa et al. 2015), in the spinal cords of Tg(olig2:dsred2) zebrafish upon injection of mRNA for the mutant OPTN and ANG variants.