DLG4 and early-onset autosomal dominant Alzheimer disease: As shown in Fig. 6B, the protein level of STX1A, SNAP25 and PSD-95 at synapses was significantly decreased in Alzheimer’s disease patients [STX1A, t(9) = 3.2, P < 0.05; SNAP25, t(9) = 3.4, P < 0.01; PSD-95, t(9) = 2.7, P < 0.05, t-test], while VAMP2 protein level was not significantly changed [t(9) = 1.7, P = 0.11, t-test].