Immunochemical markers for the frog olfactory neuroepithelium

Abstract

Monoclonal antibodies (mAbs) were generated that react with the major cell types in the olfactory neuroepithelium of the frog, Rana catesbeiana. This pseudostratified epithelium consists of apical supporting cells, a middle layer of olfactory receptor neurons and a heterogeneous population of basal cells consisting of basal cells proper and globose basal cells. Both olfactory receptor neurons and globose basal cells were labelled by mAb 13-OE, which recognized the neural cell adhesion molecule NCAM. The identity of these NCAM positive cells was established by analysing regenerating olfactory epithelium and by a double-antibody labelling immunofluorescence technique. The olfactory nerve was lesioned, which induced the death of olfactory receptor neurons and the subsequent proliferation of basal cells. When the regenerating olfactory epithelium was analysed prior to the reconstitution of mature olfactory neurons, mAb 13-OE reacted specifically with globose basal cells and not the basal cells proper. Simultaneous labelling of normal olfactory epithelium with mAb 13-OE and polyclonal anti-keratin antibodies, the latter of which labels supporting cells and basal cells proper, revealed no double-labelled cells. These results further confirmed that NCAM was expressed by both globose basal cells and receptor neurons but not by other cell types within the epithelium. Additional cell types in the olfactory epithelium reacted with other new mAbs: 4-OE, 5-OE, 7-OE and 9-OE. Supporting cells were stained by mAb 4-OE. Olfactory receptor neurons and the entire population of basal cells were immunoreactive with mAb 7-OE. The cilia and knobs of receptor neurons were strongly immunoreactive with mAb 5-OE whereas mAb 9-OE selectively stained olfactory knobs and not the cilia on these chemosensory cells. These studies are a first step towards experimental approaches designed to elucidate the mechanisms underlying the unique proliferative properties of the olfactory neuroepithelium in frog.