Significant decrease in neuronal viability and significant increase in LDH activity following exposure to ALS–CSF compared to controls (P < 0.001). Non-significant increase in proportion of BCL2-positive neurons but significant increases in proportion of Bax-positive and caspase-9-positive neurons (P < 0.05) following exposure to ALS–CSF compared to controls. This evidence concerns the gene CASP9 and amyotrophic lateral sclerosis.