C9orf72 and amyotrophic lateral sclerosis: Basso et al. (2013) found that superoxide dismutase 1, encoded by SOD1, which is the most common causative gene in the Chinese patients (Chen et al., 2021), could be transferred from astrocyte-derived exosomes to spinal neurons, inducing selective motor neuron death (Basso et al., 2013). Moreover, Westergard et al. (2016) found evidence for cell-to-cell spreading of dipeptide repeat proteins (DRPs) produced by pathologic C9orf72 hexanucleotide repeat expansions (HREs) via exosome-dependent in the spinal motor neurons derived from induced pluripotent stem cells from patients with ALS.