GFAP and amyotrophic lateral sclerosis: However, our data and that of others (Rossi et al., 2008; Díaz-Amarilla et al., 2011; Cunha et al., 2018; Gomes et al., 2020) are consistent with a downregulation of GFAP in the presence of reactive markers that also include increased Ki-67, together contributing to denominate astrocytes in ALS as having an aberrant phenotype.