EXPRESSION PATTERNS OF RAF-1 SUGGEST MULTIPLE ROLES IN TOOTH DEVELOPMENT

Raf-1, the product of proto-oncogene c-raf-1, has key roles in the sig nal transduction pathways within the cell. The molecular mechanisms of tooth development in the mouse embryo are not known in detail. We exa mined the expression of Raf-1 during subsequent tooth development by i mmunohistochemical analysis. In mouse embryos at days 12.5 post-coitum (p.c.), Raf-1 was expressed in the dental invaginating epithelium. At p.c. 13.5 (bud stage), Raf-1 was also expressed in the epithelial cel ls of the enamel organ, but not in the mesenchyme of the dental papill a, We added antiproliferating cell nuclear antigen (PCNA) antibody as a marker for proliferating cells at early stages of tooth development. At p.c. 12.5 and p.c. 13.5, the staining patterns were very similar t o that for Raf-1. At p.c. 15.5 (cap stage), Raf-1 could not be detecte d. At p.c. 17.5 (bell stage), Raf-1 was expressed in both the odontobl astic and subodontoblastic cells of the dental papilla. However, Raf-1 was not found in the epithelial cells of the enamel organ, We also ad ded antitype I collagen antibody as a marker for odontoblasts differen tiation, The staining pattern for type I collagen antibody as a marker for odontoblasts differentiation. The staining patten for type I coll agen in odontoblasts was almost the same as for Raf-1. The results sug gest that Raf-1 may play some roles in both cell proliferation and dif ferentiation at different stages of tooth germ development.