GFAP and amyotrophic lateral sclerosis: However, as in ALS patients and the SOD1G93A mouse30, 31, 32, 33, 34, MN degeneration in the τONhFUS mutants was associated with marked astrocytosis and microgliosis, evidenced by an increase in both glial fibrillary acidic protein (GFAP) and Iba1 immunoreactivity in the ventral horn of the τONhFUSR521C and hFUSP525L mutants relative to the τONhFUSWT controls (Supplementary Fig. 1B).