EXPRESSION OF THE NEURAL CELL-ADHESION MOLECULE (NCAM) DURING 2ND-MOLAR AND 3RD-MOLAR DEVELOPMENT IN THE MOUSE

Distribution of the neural cell adhesion molecule (NCAM) during the de velopment of the mandibular second- and third-molars of the mouse was studied by indirect immunofluorescence techniques. At the initial stag e, NCAM was intensely expressed by the mesenchymal cells surrounding t he dental lamina, and by the cap stage NCAM expression by the mesenchy mal cells became restricted to the dental follicle. After that, in add ition to the follicular mesenchyme, some cells in the basal part of th e dental papilla showed NCAM-immunoreactivity for a while after the ha rd tissue formation had started. During root formation, the follicular cells lost NCAM first from the level of the cervical root and later f rom the coronal part, while an additional NCAM positive area appeared deep in the dental papilla. Even after the teeth had erupted, NCAM was expressed in the tissue surrounding the apical root and in the pulp c ore. During the initial and bud stages, the pattern of NCAM expression in the second and third molars was different from that in the first m olar, where NCAM was found only after the late bud stage; while from t he cap stage onward, it changed in the same sequence as in the first m olar. The different pattern of NCAM expression implies that there is a difference in developmental events between the early stages of the fi rst and the other two molars. On the other hand, the common sequence o f NCAM expression in the tooth germs later than the cap stage suggests that NCAM plays an essential role in the formation of the basic struc ture of the teeth and periodontal tissues.