C9orf72 and frontotemporal dementia: In addition to these RNA-mediated toxic mechanisms, the decreased levels of C9ORF72 transcripts in brain tissue of C9ORF72 FTD/ALS individuals, together with the characteristic neuropathology observed in animal models for gene loss-of-function, indicate that also C9ORF72 haploinsufficiency is implicated in this disease [94,95].