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Jussila M, Aalto AJ, Sanz Navarro M, Shirokova V, Balic A, Kallonen A, Ohyama T, Groves AK, Mikkola ML, Thesleff I. Suppression of epithelial differentiation by Foxi3 is essential for molar crown patterning. Development 2015; 142:3954-63. [PMID: 26450968 DOI: 10.1242/dev.124172] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 09/27/2015] [Indexed: 12/27/2022]
Abstract
Epithelial morphogenesis generates the shape of the tooth crown. This is driven by patterned differentiation of cells into enamel knots, root-forming cervical loops and enamel-forming ameloblasts. Enamel knots are signaling centers that define the positions of cusp tips in a tooth by instructing the adjacent epithelium to fold and proliferate. Here, we show that the forkhead-box transcription factor Foxi3 inhibits formation of enamel knots and cervical loops and thus the differentiation of dental epithelium in mice. Conditional deletion of Foxi3 (Foxi3 cKO) led to fusion of molars with abnormally patterned shallow cusps. Foxi3 was expressed in the epithelium, and its expression was reduced in the enamel knots and cervical loops and in ameloblasts. Bmp4, a known inducer of enamel knots and dental epithelial differentiation, downregulated Foxi3 in wild-type teeth. Using genome-wide gene expression profiling, we showed that in Foxi3 cKO there was an early upregulation of differentiation markers, such as p21, Fgf15 and Sfrp5. Different signaling pathway components that are normally restricted to the enamel knots were expanded in the epithelium, and Sostdc1, a marker of the intercuspal epithelium, was missing. These findings indicated that the activator-inhibitor balance regulating cusp patterning was disrupted in Foxi3 cKO. In addition, early molar bud morphogenesis and, in particular, formation of the suprabasal epithelial cell layer were impaired. We identified keratin 10 as a marker of suprabasal epithelial cells in teeth. Our results suggest that Foxi3 maintains dental epithelial cells in an undifferentiated state and thereby regulates multiple stages of tooth morphogenesis.
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Affiliation(s)
- Maria Jussila
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Anne J Aalto
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Maria Sanz Navarro
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Vera Shirokova
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Anamaria Balic
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Aki Kallonen
- Division of Materials Physics, Department of Physics, University of Helsinki, PO Box 64, Helsinki 00014, Finland
| | - Takahiro Ohyama
- Department of Otolaryngology, Head & Neck Surgery and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033-4503, USA
| | - Andrew K Groves
- Program in Developmental Biology, Department of Molecular and Human Genetics and Department of Neuroscience, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Marja L Mikkola
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
| | - Irma Thesleff
- Research Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Biocenter 1, PO Box 56, Helsinki 00014, Finland
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102
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Liu Y, Feng J, Li J, Zhao H, Ho TV, Chai Y. An Nfic-hedgehog signaling cascade regulates tooth root development. Development 2015; 142:3374-82. [PMID: 26293299 DOI: 10.1242/dev.127068] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 07/31/2015] [Indexed: 01/09/2023]
Abstract
Coordination between the Hertwig's epithelial root sheath (HERS) and apical papilla (AP) is crucial for proper tooth root development. The hedgehog (Hh) signaling pathway and Nfic are both involved in tooth root development; however, their relationship has yet to be elucidated. Here, we establish a timecourse of mouse molar root development by histological staining of sections, and we demonstrate that Hh signaling is active before and during root development in the AP and HERS using Gli1 reporter mice. The proper pattern of Hh signaling activity in the AP is crucial for the proliferation of dental mesenchymal cells, because either inhibition with Hh inhibitors or constitutive activation of Hh signaling activity in transgenic mice leads to decreased proliferation in the AP and shorter roots. Moreover, Hh activity is elevated in Nfic(-/-) mice, a root defect model, whereas RNA sequencing and in situ hybridization show that the Hh attenuator Hhip is downregulated. ChIP and RNAscope analyses suggest that Nfic binds to the promoter region of Hhip. Treatment of Nfic(-/-) mice with Hh inhibitor partially restores cell proliferation, AP growth and root development. Taken together, our results demonstrate that an Nfic-Hhip-Hh signaling pathway is crucial for apical papilla growth and proper root formation. This discovery provides insight into the molecular mechanisms regulating tooth root development.
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Affiliation(s)
- Yang Liu
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA Department of Prosthodontics, Peking University School and Hospital of Stomatology, Haidian District, Beijing 100081, People's Republic of China
| | - Jifan Feng
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Jingyuan Li
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA Molecular Laboratory for Gene Therapy and Tooth Regeneration, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, Capital Medical University School of Stomatology, Beijing 100050, People's Republic of China
| | - Hu Zhao
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Thach-Vu Ho
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Yang Chai
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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