GFAP and neuromyelitis optica: However, the astrocyte cytoplasmic marker GFAP was significantly enhanced in the ventral horn after 6 days of hsAQP4-IgG injection (Supplementary Fig. 2c), consistent with sublytic histopathological observations in NMO patients25 and with neuropathology induced by CNS application of hsAQP4-IgG in rodents26–28.