Consistent with the involvement of mRNA export factors in (G4C2)58 toxicity, expression of (G4C2)58 in mammalian cells and Drosophila resulted in nuclear retention of RNA, which was also identified in iPSC-derived neurons from C9orf72-ALS cases (Freibaum et al., 2015). The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.