GAP43 and Alzheimer disease: Moreover, CSF Ng was the best predictor of amyloid pathology, assessed by 18F-flutemetamol PET and 18F-flortaucipir PET, compared to the presynaptic markers SNAP25 and GAP43 which could be related to the fact that postsynaptic glutamate receptor trafficking has been shown to be a prime initial target for Aβ, thus suggesting that postsynaptic terminals might be more affected by amyloid pathology in early stages of Alzheimer’s disease [25].