PPIB and Alzheimer disease: The most prominent result of these assays, as with studies of total NRXN3, α-NRXN3, and β-NRXN3 mRNA levels, was the reduced expression that was found for most of the isoforms in the AD postmortem middle frontal gyrus (MFG), middle temporal gyrus (MTG), and hippocampus (HIP) (Fig. 3c).