C9orf72 and frontotemporal dementia: Most recent studies have suggested that the nuclear-cytoplasmic transport is disrupted by the hexanucleotide repeat expansion (HRE) GGGGCC (G4C2) in C9orf72, which causes ALS and frontotemporal dementia (FTD) (Zhang et al., 2015; Freibaum et al., 2015; Jovičić et al., 2015).