SLC44A4 and Alzheimer disease: Concentrations of all synaptic markers were significantly increased in the AD biomarker group compared to the control group except for synaptotagmin-1 where there was only a trend to higher levels: mean (standard deviation) Ng22, 232.2 (138.9) vs 137.6 (95.9) pg/ml; Ng36, 225.5 (148.8) vs 130.0 (80.9) pg/ml; SNAP-25tot, 71.4 (27.9) vs 53.5 (11.7) pM; SNAP-25aa40, 14.0 (6.3) vs 7.9 (2.3) pM; and synaptotagmin-1, 287.7 (156.0) vs 238.3 (71.4) pM (Fig. 1, Tables 2 and 3).