RTN4 and amyotrophic lateral sclerosis: Depleted are general promoters of neurodifferentiation and axonal and dendritic maintenance (CAP2, ENC1, MLLT11, OLFM1, VSNL1), with clear implications for neuronal survival, but also several inhibitors of differentiation and promoters of cell proliferation (BEX1, CHN1, RTN1, RTN4, NPTN), whose role in ALS pathogenesis is ambiguous.