Sonic Hedgehog Signaling is Important in Tooth Root Development

Abstract

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.

Get full access to this article

View all access options for this article.

References

Barnes EA, Kong M, Ollendorff V, Donoghue DJ (2001). Patched1 interacts with cyclin B1 to regulate cell cycle progression. EMBO J 20:2214–2223.

Bitgood MJ, McMahon AP (1995). Hedgehog and Bmp genes are coexpressed at many diverse sites of cell-cell interaction in the mouse embryo. Dev Biol 172:126–138.

Chiang C, Litingtung Y, Lee E, Young KE, Corden JL, Westphal H, et al. (1996). Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function. Nature 383:407–413.

Cobourne MT, Hardcastle Z, Sharpe PT (2001). Sonic hedgehog regulates epithelial proliferation and cell survival in the developing tooth germ. J Dent Res 80:1974–1979.

Cohen MM Jr (2003). The hedgehog signaling network. Am J Med Genet A 123:5–28.

Dassule HR, McMahon AP (1998). Analysis of epithelial-mesenchymal interactions in the initial morphogenesis of the mammalian tooth. Dev Biol 202:215–227.

Dassule HR, Lewis P, Bei M, Maas R, McMahon AP (2000). Sonic hedgehog regulates growth and morphogenesis of the tooth. Development 127:4775–4785.

Fujiwara N, Tabata MJ, Endoh M, Ishizeki K, Nawa T (2005). Insulin-like growth factor^-I stimulates cell proliferation in the outer layer of Hertwig’s epithelial root sheath and elongation of the tooth root in mouse molars in vitro. Cell Tissue Res 320:69–75.

Goodrich LV, Milenković L, Higgins KM, Scott MP (1997). Altered neural cell fates and medulloblastoma in mouse patched mutants. Science 277:1109–1113.

10.

Gritli-Linde A, Bei M, Maas R, Zhang XM, Linde A, McMahon AP (2002). Shh signaling within the dental epithelium is necessary for cell proliferation, growth and polarization. Development 129:5323–5337.

11.

Hahn H, Wicking C, Zaphiropoulos PG, Gailani MR, Shanley S, Chidambaram A, et al. (1996). Mutations of the human homolog of Drosophila patched in the nevoid basal cell carcinoma syndrome. Cell 85:841–851.

12.

Hardcastle Z, Mo R, Hui CC, Sharpe PT (1998). The Shh signalling pathway in tooth development: defects in Gli2 and Gli3 mutants. Development 125:2803–2811.

13.

Hardcastle Z, Hui CC, Sharpe PT (1999). The Shh signalling pathway in early tooth development. Cell Mol Biol (Noisy-le-grand) 45:567–578.

14.

Ingham PW, McMahon AP (2001). Hedgehog signaling in animal development: paradigms and principles. Genes Dev 15:3059–3087.

15.

Jernvall J, Thesleff I (2000). Reiterative signaling and patterning during mammalian tooth morphogenesis. Mech Dev 92:19–29.

16.

Makino S, Masuya H, Ishijima J, Yada Y, Shiroishi T (2001). A spontaneous mouse mutation, mesenchymal dysplasia (mes), is caused by a deletion of the most C-terminal cytoplasmic domain of patched (ptc). Dev Biol 239:95–106.

17.

Marigo V, Johnson RL, Vortkamp A, Tabin CJ (1996a). Sonic hedgehog differentially regulates expression of GLI and GLI3 during limb development. Dev Biol 180:273–283.

18.

Marigo V, Scott MP, Johnson RL, Goodrich LV, Tabin CJ (1996b). Conservation in hedgehog signaling: induction of a chicken patched homolog by Sonic hedgehog in the developing limb. Development 122:1225–1233.

19.

McMahon AP, Ingham PW, Tabin CJ (2003). Developmental roles and clinical significance of hedgehog signaling. Curr Top Dev Biol 53:1–114.

20.

Milenković L, Goodrich LV, Higgins KM, Scott MP (1999). Mouse patched1 controls body size determination and limb patterning. Development 126:4431–4440.

21.

Motoyama J, Takabatake T, Takeshima K, Hui CC (1998). Ptch2, a second mouse Patched gene is co-expressed with Sonic hedgehog. Nat Genet 18:104–106.

22.

Steele-Perkins G, Butz KG, Lyons GE, Zeichner-David M, Kim HJ, Cho MI, et al. (2003). Essential role for NFI-C/CTF transcription-replication factor in tooth root development. Mol Cell Biol 23:1075–1084.

23.

Sweet HO, Bronson RT, Donahue LR, Davisson MT (1996). Mesenchymal dysplasia: a recessive mutation on chromosome 13 of the mouse. J Hered 87:87–95.

24.

Ten Cate AR (1996). The role of epithelium in the development, structure and function of the tissues of tooth support. Oral Dis 2:55–62.

25.

Tickle C (2003). Patterning systems—from one end of the limb to the other. Dev Cell 4:449–458.

26.

Tucker A, Sharpe P (2004). The cutting-edge of mammalian development; how the embryo makes teeth. Nat Rev Genet 5:499–508.

27.

Vaahtokari A, Åberg T, Jernvall J, Keränen S, Thesleff I (1996). The enamel knot as a signaling center in the developing mouse tooth. Mech Dev 54:39–43.

28.

Xu Q, Wilkinson DG (1999). In situ hybridization of mRNA with hapten labelled probes. In: In situ hybridization: a practical approach. 2nd ed. Wilkinson DG, editor. Oxford: Oxford University Press, pp. 87–106.

29.

Yamashiro T, Tummers M, Thesleff I (2003). Expression of bone morphogenetic proteins and Msx genes during root formation. J Dent Res 82:172–176.

30.

Zhang XM, Ramalho-Santos M, McMahon AP (2001). Smoothened mutants reveal redundant roles for Shh and Ihh signaling including regulation of L/R asymmetry by the mouse node. Cell 105:781–792.