title: Specificity protein 7 is not essential for tooth morphogenesis.
abstract: Tooth formation is a multifaceted process involving numerous interactions between oral epithelium and neural crest derived ecto-mesenchyme from morphogenesis to cyto-differentiation. The precise molecular regulator that drives the cyto-differentiation and dynamic cross-talk between the two cell types has yet to be fully understood. Runx2 along with its downstream target Sp7 are essential transcription factors for development of the mineralizing cell types. Global knockout of the Runx2 gene results in an arrest of tooth morphogenesis at the late bud stage. Like Runx2, Sp7-null mutants exhibit peri-natal lethality and are completely devoid of alveolar bone. However, the role of Sp7 in tooth development remains elusive. Here, we report the effects of Sp7 deletion on tooth formation. Surprisingly, tooth morphogenesis progresses normally until the mid bell stage in Sp7-homozygous mutants. Incisors and multi-cusped first and second molars were noted in both littermates. Thus, formation of alveolar bone is not a prerequisite for tooth morphogenesis. Tooth organs of Sp7-null however, were significantly smaller in size when compared to WT. Differentiation of both ameloblasts and odontoblasts was disrupted in Sp7-null mice. Only premature and disorganized ameloblasts and odontoblasts were noted in mutant mice. These data indicate that Sp7 is not required for tooth morphogenesis but is obligatory for the functional maturation of both ameloblasts and odontoblasts.
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama , AL , USA .
authors.forename: John C
authors.initials: JC
authors.lastname: Clarke
authors.forename: Ji-Myung
authors.initials: JM
authors.lastname: Bae
authors.forename: Mitra
authors.initials: M
authors.lastname: Adhami
authors.forename: Harunur
authors.initials: H
authors.lastname: Rashid
authors.forename: Haiyan
authors.initials: H
authors.lastname: Chen
authors.forename: Dobrawa
authors.initials: D
authors.lastname: Napierala
authors.forename: Soraya E
authors.initials: SE
authors.lastname: Gutierrez
authors.forename: Krishna
authors.initials: K
authors.lastname: Sinha
authors.forename: Benoit de
authors.initials: Bd
authors.lastname: Crombrugghe
authors.forename: Amjad
authors.initials: A
authors.lastname: Javed
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000166:cytology; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008963:Molar / Q000254:growth & development; D009024:Morphogenesis / Q000235:genetics* / Q000502:physiology; D009804:Odontoblasts / Q000166:cytology*; D009805:Odontogenesis / Q000235:genetics*; D000076182:Sp7 Transcription Factor; D014070:Tooth / Q000196:embryology / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors
keywords: Ameloblasts differentiation; gene regulation; odontoblasts; osterix; tooth development