title: Leucine rich amelogenin peptide alters ameloblast differentiation in vivo.
abstract: Highly mineralized tooth enamel develops from an extracellular matrix chiefly comprised of amelogenins formed by splicing of 7 (human) or 9 (rodent) exons secreted from specialized epithelial cells known as ameloblasts. Here we examined the role of the 59 amino acid alternatively spliced amelogenin known as leucine rich amelogenin peptide (LRAP) on enamel formation, using transgenic murine models in which LRAP overexpression is driven by an amelogenin promoter (TgLRAP). Beginning in the secretory stage of mouse amelogenesis, we found a reduced thickness of enamel matrix and a loss of Tomes' processes, followed by upregulated amelogenin mRNA expression, inhibited amelogenin secretion and loss of cell polarity. In the presecretory stage (P0) amelogenin m180 mRNA expression was increased 58 fold along with a 203 fold increase in MMP-20 expression and 3.5 and 3.2 fold increased in respectively enamelin and ameloblastin. When LRAP was overexpressed on an amelogenin knockout mouse model, the ameloblasts were not affected. Further, expression of the global chromatin organizer and transcription factor SATB1 was reduced in secretory stage TgLRAP ameloblasts. These findings identify a cellular role for LRAP in enamel formation that is not directly related to directing enamel crystal formation as is reported to be the primary function of full length amelogenins. The effect of LRAP overexpression in upregulating amelogenins, MMP-20 and SATB1, suggests a role in protein regulation critical to ameloblast secretion and matrix processing, to form a mineralized enamel matrix.
authors.affiliation: Department of Orofacial Sciences, School of Dentistry, University of California, San Francisco, CA, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Stahl
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakano
authors.forename: Seong-Oh
authors.initials: SO
authors.lastname: Kim
authors.forename: Carolyn W
authors.initials: CW
authors.lastname: Gibson
authors.forename: Thuan
authors.initials: T
authors.lastname: Le
authors.forename: Pamela
authors.initials: P
authors.lastname: DenBesten
mesh_terms: D000565:Ameloblasts / Q000187:drug effects / Q000502:physiology*; D000566:Amelogenesis / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D003746:Dental Enamel Proteins / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006652:Histological Techniques; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D036961:Matrix Attachment Region Binding Proteins / Q000378:metabolism; D053519:Matrix Metalloproteinase 20 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016133:Polymerase Chain Reaction; D055114:X-Ray Microtomography
chemical_list: D017931:DNA Primers; D003746:Dental Enamel Proteins; D036961:Matrix Attachment Region Binding Proteins; C469541:Satb1 protein, mouse; C067432:leucine-rich amelogenin peptide; D053519:Matrix Metalloproteinase 20; C507113:Mmp20 protein, mouse
keywords: Ameloblasts; Amelogenin; Enamel; LRAP; Leucine rich amelogenin peptide (LRAP); MMP20; SATB1; Transgenic mice; leucine rich amelogenin peptide; matrix metalloproteinase 20