FUS and amyotrophic lateral sclerosis: In this manuscript, we use induced pluripotent stem cell (iPSC)-derived cultures of spinal neurons (SNs), which are enriched in MNs, to demonstrate that RNA viruses exacerbate ALS phenotypes in neurons harboring the ALS-associated mutation P525L FUS. Neuronal connectivity is essential for function, and it has been shown that maintenance of MN connectivity is essential for preventing ALS phenotypes (Parone et al., 2013).