NRGN and Alzheimer disease: In addition, CSF markers of synaptic loss such as neurogranin (NG), synaptosomal-associated protein-25 (SNAP-25), and synaptotagmin-1 (SYT-1) have emerged as potential AD biomarkers as they are consistently elevated along the AD continuum [4, 5] and seem to reflect both amyloid β and tau pathology [6–8].