C9orf72 and frontotemporal dementia: STAU1 overabundance contributes to neurodegeneration by promoting hyperactivation of the mTOR pathway, endoplasmic reticulum (ER) stress, autophagy dysfunction, RNA-protein condensates, amyloidogenesis, tau phosphorylation and neuronal apoptosis in cultured neurons and animal models of ALS, ALS/FTD and SCA2 (C9orf72, Thy1-TDP-43, and ATXN2Q127) [17–19, 23–25].