Control- and age-matched human neocortex and hippocampus samples were also analyzed for mRNA abundance for the sphingomyelin synthases SGMS1 and SGMS2. Both SGMS1 and SGMS2 were observed to be downregulated in both AD neocortex and hippocampus when compared with age-matched controls (Fig. 6). Here, SGMS1 is linked to Alzheimer disease.