NEFL and amyotrophic lateral sclerosis: In parallel, the NF-L staining showed that neurite networks of control and ALS MNs were healthy with no neurite fragmentation at T0 (Supplementary Fig. 7a), while at T1 ALS neurite networks were less dense with bead-like structures all along neurites (Fig. 3a, Supplementary Fig. 7e), indicating neurite fragmentation and degeneration.