VPS4A and amyotrophic lateral sclerosis: Highlighting the utility of SIM for evaluating not only protein distribution, but also expression, western blot analyses quantitatively confirmed an increase in VPS4, but not CHMP4B nor CHMP2B protein in nuclei isolated from C9orf72 ALS/FTD and sALS iPSNs (Additional file 1: Figure S1e–h).