A subset of peripherin positive olfactory axons delineates the luteinizing hormone releasing hormone neuronal migratory pathway in developing mouse.

Luteinizing hormone releasing hormone (LHRH) neurons in the CNS are derived from cells of the olfactory placode and thereafter migrate from the olfactory pit into the diencephalon. In this study, we examined embryonic LHRH neurons and the LHRH migratory pathway for several markers. During development, N-CAM and peripherin mRNA were expressed by olfactory epithelia, but not by LHRH cells. In nasal regions, olfactory axons were not immunostained by laminin or fibronectin antibodies, but were robustly peripherin and N-CAM immunoreactive. Although the majority of these axonal tracks entered the developing olfactory bulbs, a small population of peripherin positive but N-CAM negative axons turned caudally into the developing forebrain. LHRH cells were consistently juxtaposed to these axons. We propose that this peripherin positive/N-CAM negative fiber track is the anatomical pathway upon which LHRH cells migrate from the olfactory pit into the diencephalon.