C9orf72 and amyotrophic lateral sclerosis: Reduced endocytosis and impaired endosomal/lysosomal trafficking have been demonstrated in C9orf72 knockdown cell lines [40], bone marrow-derived macrophage and microglia from C9orf72−/− mice [46], and C9orf72 ALS patient-derived fibroblasts and neurons [47].