Thus, we showed how neurons from various patients with PD (PARK2 and SNCA 3× mutations) or ALS (TDP-43N390D, TDP-43M337V, and c9orf72 mutations) display lower intracellular ATP levels than healthy neurons, resulting in a significant decrease in their axonal cytosol solubility. Here, C9orf72 is linked to amyotrophic lateral sclerosis.