DLG4 and Alzheimer disease: In the prefrontal cortex, GFAP gene expression was found to be upregulated in AD brains [29], and in CA1 pyramidal neurons gene expression of synaptophysin and PSD-95 were downregulated in individuals with MCI and AD [12], corroborating our findings of preservation of synaptophysin and PSD-95 protein expression in the resilient hippocampi.