C9orf72 and frontotemporal dementia: Four different toxic gain-of-function mouse models developed through expression of patient-derived C9orf72 containing hundreds of HREs consistently displayed intracellular RNA foci and DPRs in the CNS, though they differed in the generation of ALS/FTD disease phenotypes (Jiang et al., 2016; Liu et al., 2016; O'Rourke et al., 2015; Peters et al., 2015; Chew et al., 2015).