Gene Expression of Matrix Proteins in Cbfa1-Knockout Mice

Odontogenesis and osteogenesis are two distinct yet closely related processes that share common signalling pathways including regulatory control by Cbfa1. Although Cbfa1 is well-recognized as the master regulator of osteoblastic differentiation, little is known of its precise role during odontogenesis. We sought to clarify this by examining morphogenesis of teeth and matrix protein gene expression in cbfa1-knock-out mice at ed 17.5 and day 0 of birth, and comparing it with presumptive mandible bone-forming site. Results demonstrated morphological and functional differentiation differences between these two processes: incisor tooth germ showed morphological and functional differentiation of odontoblasts with expression of osteopontin and osteocalcin whereas the presumptive mandible bone-forming site showed lack of osteoblastic differentiation, and no expression of these two matrix proteins. Stage-specific and cytodifferentiation differences were also observed between incisor and molar tooth germs: incisor tooth germ progressed to the bell stage with odontoblast and ameloblast differentiation, and expression of tooth-specific proteins, amelogenin and dentine sialophosphoprotein, whereas molar tooth germ showed marurational arrest at bud to cap stage. Present findings suggest that 1. The transcription factor Cbfa-1 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 presumptive mandible forming region showed different patterns of gene expression of matrix proteins common to teeth and bones.