C9orf72 and frontotemporal dementia: Ultrastructural analysis by EM in the CA3 region of mice revealed a significant decrease in synaptic vesicle density per synapse and a decrease in the number of docked vesicles.144 Furthermore, a decrease in the levels of C9orf72 and synapsin is observed in the hippocampus of patient tissue (C9orf72-ALS/FTD and FTD).144