In line with the idea that PD is initiated in the gut, it has been shown that oral administration of paraquat in transgenic A53T mice triggers an increased expression of Glial fibrillary acidic protein (GFAP; a classic activation marker of astrocytes) in glial cells of the enteric nervous system before neuropathology manifestation in the brain (68). Here, GFAP is linked to Parkinson disease.