C9orf72 and amyotrophic lateral sclerosis: For instance, foci containing sense G4C2 or antisense G2C4 repeat RNA bidirectionally-transcribed from the C9orf72 expansion are observed in c9FTD/ALS postmortem brain tissues, cultured cells, and neurons, and may disrupt RNA metabolism and nucleocytoplasmic transport through sequestration of various RNA-binding proteins [11, 14, 18, 22, 23, 31, 42, 43].