Differential expression of two carbohydrate epitopes, CD15 and HNK-1, in developing vertebrate olfactory receptor neurones.

According to the view of differentiation-related alterations in the glycosylation pattern of neurones, recent studies have shown development dependent expression patterns of lactoseries carbohydrate epitopes, CD15 and HNK-1, on olfactory receptor neurones in rats and chicks. In order to evaluate a general role for these epitopes during development of vertebrate olfactory receptor neurones, this investigation focuses on the situation in the mouse, bovine and Xenopus olfactory epithelium. In all three species CD15 expression was found on a subpopulation of morphologically mature receptor cells starting at the time of initial synaptogenesis. Whereas for bovine and Xenopus the timetable of HNK-1 expression is similar to that described for the chick, suggesting involvement in pathfinding, in the mouse HNK-1 is found on immature cells when mature CD15 positive receptor cells could already be discerned. By our results a role for CD15 during establishment of synaptic contacts and for HNK-1 during their formation is suggested.