Our analysis of human spinal cord tissue revealed GPX4 gene expression, GPX4 protein levels, and GPX4 activity were all unchanged in ALS (Supplementary Fig. 4a-c), as opposed to recent reports of mildly [45] or substantially [46] diminished GPX4 protein in ALS and robust changes we detected in Gpx4 conditional knockout mice (Supplementary Fig. 4d-f). This evidence concerns the gene GPX4 and amyotrophic lateral sclerosis.