PRESENILIN-1 MESSENGER-RNA AND BETA-AMYLOID PRECURSOR PROTEIN MESSENGER-RNA ARE EXPRESSED IN THE DEVELOPING RAT OLFACTORY AND VESTIBULOCOCHLEAR SYSTEMS

The mRNA expression of presenilin-1 (PSI) and beta-amyloid precursor p rotein (beta APP) was investigated in the embryonic day 20 rat olfacto ry bulb, nasal cavity, and inner ear using in situ hybridization histo chemistry. In the olfactory bulb, PSI mRNA was strongly expressed in b oth olfactory bulb neuroepithelium and the differentiating olfactory b ulb. In contrast, beta APP mRNA was preferentially expressed in differ entiating fields. In the nasal cavity, PS1 mRNA was strongly expressed throughout the olfactory epithelium, while beta APP mRNA expression w as concentrated in the middle part of the epithelium. In the membrane labyrinth of the inner ear, although PS1 mRNA was evenly distributed i n both sensory epithelium and supporting cells, beta APP mRNA was excl usively expressed in the sensory epithelium. These data suggest that P SI is expressed earlier than beta APP, and that PS1 and beta APP co-op eratively play pivotal roles in the development of the olfactory and v estibulocochlear systems.