Between MCI ε4− and MCI ε4+, CSF Ng levels in APOE ε4 positive participants increased significantly (p < 0.001) (Figure 1), but there were no statistically significant differences between CN ε4− and CN ε4+ as well as between AD ε4− and AD ε4+ (Figure 1). Here, NRGN is linked to Alzheimer disease.