Nucleolin is a principal component of the nucleolus (Abdelmohsen and Gorospe, 2012), which was found to mislocalize with the G4C2 RNA foci in the neurons of the motor cortex of C9orf72 ALS patients, leading to nucleolar stress and impaired nucleolar function in patient cells. Here, C9orf72 is linked to amyotrophic lateral sclerosis.