NRGN and Alzheimer disease: Therefore, we can assume that APOE ε4 carriers may undergo synaptic damage that can be captured by elevated Ng concentrations and that increases the risk of AD as observed through biomarker profile which we examined by an association between Ng and tau pathology, neurofibrillary tangle formation, and neurodegeneration in the AD continuum, notions that should be tested in future research.