C9orf72 and amyotrophic lateral sclerosis: Similar to C9ORF72‐S, C9ORF72‐AS forms RNA foci in MNs and sporadically in interneurons (in frontal cortex and spinal cord) of ALS and FTD patients (DeJesus‐Hernandez et al., 2011; Gendron et al., 2013; Mizielinska et al., 2013; Zu et al., 2013).