SPP1 and amyotrophic lateral sclerosis: To determine whether activated glial cells also began to express OPN during disease progression in ALS mouse models, we compared the distributions of OPN and glial markers (Iba1 for microglia/macrophages, GFAP for astrocytes) in spinal cord sections from SOD1G93A or SOD1G85R mice with late-stage disease (Supplementary Fig. 3a).