SOD1 and amyotrophic lateral sclerosis: Consistent with original post mortem/in vivo observations, several studies based on in vitro cultures of neural cells provided evidence that astrocytes harboring ALS-associated mutated proteins, such as mutated SOD1, are toxic to primary, as well as pluripotent stem cell-derived, motor neurons, but not to other neuronal populations (Di Giorgio et al., 2007, 2008; Nagai et al., 2007; Marchetto et al., 2008).