NRGN and Alzheimer disease: As shown in Table 2, the levels of synaptic proteins such as NRGN, synaptophysin, synaptotagmin, synaptopodin, SNAP-25, AMPA4 receptor, NPTX2, NLGN1, NRXN2, p-S9-synapsin 1, synapsin 1, and MOG were lower in patients with AD.