FUNCTIONAL ANALYSIS OF TOOTH GERM DEVELOPMENT-RELATED GENES

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We previously examined the development of the mouse mandible, and demonstrated that odontogenesis occurs between embryonic day 10.5 (E 10.5) and E12. Based on the histological findings, we performed cDNA subtraction between the E10.5 and E12 mandibles to detect any differentially expressed genes which might be involved in the initiation of odontogenesis. We found Pgk-1,Ccte,Hsp86,Nucleolin,Hsc73,Frg1,N-ras,Set alpha and Hsj2 from the E10.5 mandible, and E25,ATPase6,Mum2, Thymosin beta4 and L21 from the E12 mandible to be differentially expressed genes. In situ hybridization analyses showed the expression of Set alpha, heat shock proteins (HSPs:Hsc73,Hsj2 and Hsp86), Pgk-1,Nucleolin, ATPase6, Thymosin beta4 to be detected in the developing tooth germ, thus indicating a close relationship of this gene to odontogenesis.Runx2/Cbfal knockout mice showed both a complete lack of ossification and the developmental arrest of tooth germ. We examined Runx2/Cbfa1 isoform-type specific functional r … More oles in the development of tooth germ by the administration of antisense phosphorothioate oligodioxynucleotides (S-ODNs) into cultured mouse mandibles. The administration of type II/III Runx2/Cbfa1 antisense S-ODNs into the culture media resulted in an arrest of tooth germ growth at the bud-like stage in cultured mandible taken from the 11-day-old embryos, while also causing the inhibition of the differentiation of odontogenic cells into ameloblast and odontoblast in cultured tooth germs taken from the 15-day-old embryos. The expression of dentin matrix protein 1, dentin sialophosphoprotein, amelogenin and ameloblastin was shown to be markedly suppressed in cultured tooth germ by the semi-quantitative RT PCR method. Meanwhile, no developmental arrest of tooth germ, no inhibition of gene expression, or differentiation of odontogenic cells was observed in samples treated with the type I Runx2/Cbfal antisense S-ODNs. The same findings were also observed in either the control or the sense and random sequence S-ODNs treated samples. These data indicate that the type II/III Runx2/Cbfa1 isoform is closely related to the development and differentiation of tooth germ. Less