We next addressed whether ALS motor neurons can induce C3 expression in control astrocytes by treatment with motor neuron conditioned medium (MNCM) from VCP mutant or SOD1 mutant lines compared to MNCM from control lines, differentiated using our established protocol.12 We found no significant increase in C3 expression in control astrocytes treated with either control or mutant motor neuron conditioned media (Supplementary Fig. 1). Here, C3 is linked to amyotrophic lateral sclerosis.