EPHA4 and amyotrophic lateral sclerosis: Ephrin type A receptor 4–dependent (Epha4-dependent) axon guidance in development has been extensively investigated; however, its importance is under intense investigation in neurological disorders, including traumatic brain injury (TBI) (13, 14), Alzheimer’s disease (15), amyotrophic lateral sclerosis (16), and ischemia (17).