C9orf72 and frontotemporal dementia: Since the discovery of a repeat expansion in the C9orf72-SMCR8 complex subunit (C9orf72) [1, 2], researchers have worked diligently to unravel the mechanisms underlying C9orf72-related diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).