C9orf72 and frontotemporal dementia: In this regard, the RQC rate-limiting factor zinc finger protein 598, E3 ubiquitin ligase (ZNF598), has been shown to have a neuroprotective function in C9-ALS/FTD, since it co-translationally regulates the expression of C9orf72-derived protein to promote its degradation via the ubiquitin–proteasome pathway and to suppress proapoptotic caspase-3 activation, while ALS-linked mutant ZNF598R69C showed a loss of this function [41] (Figure 2A).