title: Core binding factor beta functions in the maintenance of stem cells and orchestrates continuous proliferation and differentiation in mouse incisors.
abstract: Rodent incisors grow continuously throughout life, and epithelial progenitor cells are supplied from stem cells in the cervical loop. We report that epithelial Runx genes are involved in the maintenance of epithelial stem cells and their subsequent continuous differentiation and therefore growth of the incisors. Core binding factor β (Cbfb) acts as a binding partner for all Runx proteins, and targeted inactivation of this molecule abrogates the activity of all Runx complexes. Mice deficient in epithelial Cbfb produce short incisors and display marked underdevelopment of the cervical loop and suppressed epithelial Fgf9 expression and mesenchymal Fgf3 and Fgf10 expression in the cervical loop. In culture, FGF9 protein rescues these phenotypes. These findings indicate that epithelial Runx functions to maintain epithelial stem cells and that Fgf9 may be a target gene of Runx signaling. Cbfb mutants also lack enamel formation and display downregulated Shh mRNA expression in cells differentiating into ameloblasts. Furthermore, Fgf9 deficiency results in a proximal shift of the Shh expressing cell population and ectopic FGF9 protein suppresses Shh expression. These findings indicate that Shh as well as Fgf9 expression is maintained by Runx/Cbfb but that Fgf9 antagonizes Shh expression. The present results provide the first genetic evidence that Runx/Cbfb genes function in the maintenance of stem cells in developing incisors by activating Fgf signaling loops between the epithelium and mesenchyme. In addition, Runx genes also orchestrate continuous proliferation and differentiation by maintaining the expression of Fgf9 and Shh mRNA.
authors: Department of Orthodontics, Science of Functional Recovery and Reconstruction, Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors: Hiroshi
authors: H
authors: Kurosaka
authors: Md Nurul
authors: MN
authors: Islam
authors: Koh-Ichi
authors: K
authors: Kuremoto
authors: Satoru
authors: S
authors: Hayano
authors: Masahiro
authors: M
authors: Nakamura
authors: Noriaki
authors: N
authors: Kawanabe
authors: Takeshi
authors: T
authors: Yanagita
authors: David P C
authors: DP
authors: Rice
authors: Hidemitsu
authors: H
authors: Harada
authors: Ichiro
authors: I
authors: Taniuchi
authors: Takashi
authors: T
authors: Yamashiro
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D049109:Cell Proliferation; D050657:Core Binding Factor alpha Subunits / Q000235:genetics / Q000378:metabolism; D050658:Core Binding Factor beta Subunit / Q000235:genetics / Q000378:metabolism*; D051526:Fibroblast Growth Factor 10 / Q000235:genetics / Q000378:metabolism; D051518:Fibroblast Growth Factor 3 / Q000235:genetics / Q000378:metabolism; D051525:Fibroblast Growth Factor 9 / Q000235:genetics / Q000378:metabolism; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007180:Incisor / Q000166:cytology*; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D055114:X-Ray Microtomography
chemical_list: C493693:Cbfb protein, mouse; D050657:Core Binding Factor alpha Subunits; D050658:Core Binding Factor beta Subunit; C496464:Fgf10 protein, mouse; C489197:Fgf3 protein, mouse; C496460:Fgf9 protein, mouse; D051526:Fibroblast Growth Factor 10; D051518:Fibroblast Growth Factor 3; D051525:Fibroblast Growth Factor 9; D053823:Hedgehog Proteins; C465570:Shh protein, mouse