In a recent study, the levels of Ng and amyloid precursor protein cleaving enzyme (BACE1) in CSF and plasma, together with Aβ40, Aβ42, and t-tau in the CSF of AD patients (n = 23), GPI patients (n = 55), and NS patients (n = 13) were tested (Zhang et al., 2020). Here, NRGN is linked to Alzheimer disease.