SYT1 and Alzheimer disease: In the present study, two of the presynaptic proteins, SNAP25 and GAP43, were decreased in the brains of 5×FAD mice, while synaptotagmin 1 and the postsynaptic protein, neurogranin, did not show any significant changes, which is consistent with the finding that presynaptic alteration is preferentially involved in AD [87].