title: Gene expression and dental enamel structure in developing mouse incisor.
abstract: At the mouse incisor tip the initially differentiated ameloblasts produce a thin, prism-free enamel, while further apically, in the immediate adjacent segment, the enamel thickness increases and the four-layered enamel of mouse incisor is formed. Comparative gene-expression profiling was carried out on RNA isolated from these two segments of incisor tooth germs at embryonic day (E)17.5 and at postnatal days (P)0, 1, 2, and 10 using microarrays to measure messenger RNA (mRNA) and microRNA (miRNA) species present in the segments. Validation of expression data was achieved using real-time reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. Bioinformatic data suggested enhanced cellular apoptosis in the incisal tip segment, which, together with diminished expression of the Amelx and Enam genes, may contribute to the production of the thin enamel seen in this tooth segment. For genes exhibiting higher levels of expression in the adjacent segment where complex enamel is being formed, bioinformatic analysis suggested significant associations with cellular functions involving the actin cytoskeleton, cellular development, morphology, and movement. This is suggested to reflect that ameloblasts with Tomes' process are being organized in transverse rows, facilitating the transverse movement that results in prism decussation in the inner enamel of the adjacent segment. Bioinformatic analysis of miRNA expression data lends support to these suggestions.
authors.affiliation: Department of Oral Biology, University of Oslo, Box 1052 Blindern, 0316 Oslo, Norway.
authors.forename: Amer
authors.initials: A
authors.lastname: Sehic
authors.forename: Steinar
authors.initials: S
authors.lastname: Risnes
authors.forename: Qalb-E-Saleem
authors.initials: QE
authors.lastname: Khan
authors.forename: Cuong
authors.initials: C
authors.lastname: Khuu
authors.forename: Harald
authors.initials: H
authors.lastname: Osmundsen
mesh_terms: D000199:Actins / Q000032:analysis; D000565:Ameloblasts / Q000166:cytology; D000566:Amelogenesis / Q000235:genetics; D053523:Amelogenin / Q000032:analysis; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics; D064026:Calbindins; D048708:Cell Growth Processes / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D003599:Cytoskeleton / Q000235:genetics; D003743:Dental Enamel / Q000196:embryology* / Q000648:ultrastructure; D003746:Dental Enamel Proteins / Q000032:analysis; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D005865:Gestational Age; D007180:Incisor / Q000196:embryology* / Q000648:ultrastructure; D007610:Kallikreins / Q000032:analysis; D053519:Matrix Metalloproteinase 20 / Q000032:analysis; D051379:Mice; D035683:MicroRNAs / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D009419:Nerve Tissue Proteins / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D014083:Tooth Germ / Q000196:embryology* / Q000648:ultrastructure
chemical_list: D000199:Actins; C490890:Ambn protein, mouse; D053523:Amelogenin; C507200:Amelx protein, mouse; D064026:Calbindins; D003746:Dental Enamel Proteins; D035683:MicroRNAs; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; C038456:tuftelin; D007610:Kallikreins; C120801:kallikrein 4; D053519:Matrix Metalloproteinase 20; C507113:Mmp20 protein, mouse