Abstract: Objective: To study the expressions of cell polarity related proteins CDC42 and PAR3 during tooth germ development in the mice, and to discuss their possible roles during tooth development in the mice. Methods: The whole heads were obtained from the mouse embryo on the days 13.5,14.5,16.5 and 18.5 (E13.5, E14.5, E16.5 and E18.5) and the mice on the postnatal days 1 (PN1) and 5(PN5). The tissues were fixed in paraformaldehyde, decalcified, dehydrated, embedded in paraffin, and sectioned.The histology of tooth germ was observed by HE staining. The expressions of CDC42 and PAR3 during tooth germ development were detected by immunohistochemistry staining. Results: The HE staining results showed that E13.5, E14.5, E16.5 and E18.5 were the bud stage,the cap stage,the early and the late bell stage of tooth germ development, respectively;the tooth germ of PN1 mice showed the matured odontoblasts and ameloblasts;the tooth germ of PN5 mice showed the completed tooth crown development. The immunohistochemistry staining results showed that CDC42 expressed in the tooth germ of the mice at E13.5, E14.5 and E16.5;the CDC42 expression at E 18.5 was reduced compared with E13.5,E14.5 and E16.5; CDC42 mainly expressed in the odontoblasts and ameloblasts of the tooth germ of the mice at PN1 and PN5; PAR3 weakly expressed in the tooth germ of the mice at E13.5 and E14.5,and it was increased at E16.5 and E18.5. At PN1 and PN5, the expressions of PAR3 were decreased compared with E18.5. Conclusion: CDC42 and PAR3 participat in the mouse tooth development; during the early stage of tooth germ development, they may be involved in the proliferation and migration of mouse dental germ; during the late stage,CD42 and PAR3 may be involved in the differentiation of the odontoblasts and the ameloblasts, especially in the establishment and maintenance of cell polarity.

Key words: cell polarity related protein, CDC42, odontoblast, PAR3, tooth germ development, ameloblast