RESUMO
BACKGROUND AND OBJECTIVE: The tooth root is one of the critical parts to maintain tooth function; however, the molecular mechanisms of root development remain unknown. We aimed to identify specific factors for root morphogenesis using a newly developed experimental system. MATERIAL AND METHODS: Tentative cementoblasts and periodontal ligament cells from mouse mandibular molars were isolated using laser capture microdissection. More than 500 cementoblasts and periodontal ligament cells were separately captured. After RNA extraction and amplification, mRNA expression in isolated cementoblasts was compared with that of periodontal ligament cells by cDNA microarray analysis. Then, putative cementoblast-specific genes were subjected to in situ hybridization analysis to confirm the results in mouse mandible. RESULTS: Approximately 2000 genes were differentially expressed between these tissues. Among those genes, zinc finger helicase (ZFH), also termed chromodomain-helicase-DNA-binding protein 3 (Chd3), was one of the highly expressed transcripts in tentative cementoblasts. In situ hybridization revealed that ZFH/Chd3 was strongly expressed in Hertwig's epithelial root sheath rather than in cementum. Moreover, its expression disappeared when root formation was advanced in the first molar. In contrast, Chd3 was continuously expressed in dental epithelial cells of the cervical loop, in which root extension is never terminated. CONCLUSION: These results suggest that ZFH/Chd3 might play an important role in tooth root development and subsequent cementogenesis.
Assuntos
DNA Helicases/genética , Proteínas de Ligação a DNA/genética , Odontogênese/genética , Raiz Dentária/crescimento & desenvolvimento , Ameloblastos/fisiologia , Animais , Técnicas de Cultura de Células , Montagem e Desmontagem da Cromatina/genética , Cemento Dentário/fisiologia , Órgão do Esmalte/crescimento & desenvolvimento , Células Epiteliais/fisiologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento/genética , Incisivo/crescimento & desenvolvimento , Microdissecção e Captura a Laser , Masculino , Mandíbula/citologia , Camundongos , Camundongos Endogâmicos ICR , Dente Molar/crescimento & desenvolvimento , Morfogênese/genética , Hibridização de Ácido Nucleico , Análise de Sequência com Séries de Oligonucleotídeos , Ligamento Periodontal/citologia , Germe de Dente/crescimento & desenvolvimentoRESUMO
Hertwig's epithelial root sheath (HERS) is important for tooth root formation, but the molecular basis for the signaling of root development remains uncertain. We hypothesized that Sonic hedgehog (Shh) signaling is involved in the HERS function, because it mediates epithelial-mesenchymal interactions during embryonic odontogenesis. We examined the gene expression patterns of Shh signaling in murine developing molar roots. Shh and Patched2 transcripts were identified in the HERS, whereas Patched1, Smoothened, and Gli1 were expressed in the proliferative dental mesenchyme in addition to the HERS. To confirm whether Shh signaling physiologically functions in vivo, we analyzed mesenchymal dysplasia (mes) mice carrying an abnormal C-terminus of the PATCHED1 protein. In the mutant, cell proliferation was repressed around the HERS at 1 wk. Moreover, the molar eruption was disturbed, and all roots were shorter than those in control littermates at 4 wks. These results indicate that Shh signaling is important in tooth root development. Abbreviations used: BrdU, 5-bromo-2'-deoxyuridine; HERS, Hertwig's epithelial root sheath; NFI-C/CTF, nuclear factor Ic/CAAT box transcription factor; PCNA, proliferating cell nuclear antigen; Ptc, patched; Shh, sonic hedgehog; Smo, smoothened.
Assuntos
Odontogênese/genética , Raiz Dentária/crescimento & desenvolvimento , Transativadores/genética , Transativadores/fisiologia , Animais , Proliferação de Células , Epitélio , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Hedgehog , Hibridização In Situ , Fatores de Transcrição Kruppel-Like/genética , Fatores de Transcrição Kruppel-Like/fisiologia , Mesoderma/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Morfogênese/genética , Receptores Patched , Receptor Patched-1 , Receptor Patched-2 , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/fisiologia , Transdução de Sinais , Erupção Dentária/genética , Proteína GLI1 em Dedos de ZincoRESUMO
Nuclear factor kappa B (NF-κB) signaling plays critical roles in many physiological and pathological processes, including regulating organogenesis. Down-regulation of NF-κB signaling during development results in hypohidrotic ectodermal dysplasia. The roles of NF-κB signaling in tooth development, however, are not fully understood. We examined mice overexpressing IKKß, an essential component of the NF-κB pathway, under keratin 5 promoter (K5-Ikkß). K5-Ikkß mice showed supernumerary incisors whose formation was accompanied by up-regulation of canonical Wnt signaling. Apoptosis that is normally observed in wild-type incisor epithelium was reduced in K5-Ikkß mice. The supernumerary incisors in K5-Ikkß mice were found to phenocopy extra incisors in mice with mutations of Wnt inhibitor, Wise. Excess NF-κB activity thus induces an ectopic odontogenesis program that is usually suppressed under physiological conditions.