FUS and frontotemporal dementia: The first mechanistic explanation for a role of NIRs in ALS/FTD was reported when TNPO1 was found to inhibit phase separation and fibrillization of recombinant FUS by binding its PY-NLS, which is abrogated by ALS-associated FUS-NLS mutations and loss of FUS arginine methylation, as seen in FTD-FUS [18–21].