NRN1 and Alzheimer disease: In animal models of both chronic stress and AD, viral-mediated overexpression of NRN1 has produced robust neuroprotective effects, including the prevention of dendritic spine loss, reversal of depressive-like behavior, and restoration of cognitive function (Son et al., 2012; An et al., 2014; Choi et al., 2014; Lee et al., 2021; Song et al., 2025).