Gene Expression of Matrix Proteins during Tooth Germ Development in Cbfa1 Knockout Mice

Cbfa1 (Runx2) is a well recognized factor for osteoblast differentiation. However its role during odontogenesis is not well known. We examined the morphogenesis of tooth and gene expression of matrix protein in Cbfa1-knockout mice at ed 17.5 and day 0 of birth and compared them with mandible bone development. Incisor tooth germ showed morphological and functional differentiation of odontoblasts with expression of osteopontin and osteocalcin, whereas the mandible bone-forming site displayed lack of osteoblastic differentiation, and absence of osteopontin and osteocalcin expression. Stage-specific and cytodifferentiation differences demonstrated: incisor tooth germ progressed to the bell stage, whereas molar tooth germ showed maturational arrest at bud to cap stage. Present findings suggest that 1. Cbfa1 is associated with morphogenesis of teeth and matrix protein gene expression, 2. Compared to the incisor tooth germ, the molar tooth germ is more strongly subjected to control by Cbfa1, and 3. In Cbfa1-knockout mice, the odontoblast-like cells in the incisor and the spindle cells in the mandible forming region showed different patterns of gene expression of matrix proteins which are common to both teeth and bones.