NRGN and early-onset autosomal dominant Alzheimer disease: In animal models (i.e., 5XFAD mice) and patients with Alzheimer’s disease, Ng is downregulated in frontal cortex and hippocampus, and viral-mediated restoration of its levels in the hippocampus of 5XFAD mice contributes to the enhancement of cognitive functions [38], further demonstrating a strong correlation between brain Ng expression and cognitive performances.