C9orf72 and amyotrophic lateral sclerosis: Our data shows that C9orf72 loss of function causes reduced levels of synapsin at presynaptic sites in primary hippocampal neuron cultures as well as in the mossy fibre region of the hippocampus of C9orf72-KO mice and ALS/FTD patients (Figs. 3, 4, 5, 6).