Presenilin 1 (PSNL1) is a novel causative gene for early-onset familial Alzheimer's disease (EOFAD). We have examined the regional and cellular distribution of PSLN1 gene expression in normal human and rat tissues. In situ hybridization and Northern blot analysis showed that PSNL1 mRNA was ubiquitously expressed in many different organs. We also demonstrated that PSNL1 mRNA was expressed predominantly in the neuronal cells of the central nervous system, but only at low-level in glial cells. Furthermore, the distribution of PSNL1 mRNA in human and rodent brains was similar.