title: Truncated amelogenin and LRAP transgenes improve Amelx null mouse enamel.
abstract: Amelogenin is the most abundant enamel protein involved in enamel mineralization. Our goal was to determine whether all three regions of amelogenin (N-terminus, C-terminus, central core) are required for enamel formation. Amelogenin RNA is alternatively spliced, resulting in at least 16 different amelogenin isoforms in mice, with M180 and LRAP expressed most abundantly. Soon after secretion by ameloblasts, M180 is cleaved by MMP20 resulting in C-terminal truncated (CTRNC) amelogenin. We aimed to determine whether the 2 transgenes (Tg), LRAP and CTRNC together, can improve LRAPTg/Amelx-/- and CTRNCTg/Amelx-/- enamel thickness and prism organization, which were not rescued in Amelx-/- enamel. We generated CTRNCTg/LRAPTg/Amelx-/- mice and analyzed developing and mature incisor and molar enamel histologically, by microCT, SEM and microhardness testing. CTRNCTg and LRAPTg overexpression together significantly improved the enamel phenotype of LRAPTg/Amelx-/- and CTRNCTg/Amelx-/- mouse enamel, however enamel microhardness was recovered only when M180Tg was expressed, alone or with LRAPTg. We determined that both LRAP and CTRNC, which together express all three regions of the amelogenin protein (N-terminus, C-terminus and hydrophobic core) contribute to the final enamel thickness and prism organization in mice.
authors.affiliation: Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Ren
authors.affiliation: Department of Mineralized Tissue Biology, The Forsyth Institute, 245 First Street, Cambridge, MA, USA; Department of Developmental Biology, Harvard School of Dental Medicine, 188 Longwood Ave, Boston, MA 02115, USA. Electronic address: mpugach@forsyth.org.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Pugach
mesh_terms: D053523:Amelogenin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D003743:Dental Enamel / Q000000981:diagnostic imaging* / Q000254:growth & development; D005260:Female; D007180:Incisor / Q000254:growth & development; D008297:Male; D051379:Mice; D008963:Molar / Q000254:growth & development; D000072417:Protein Domains; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D019076:Transgenes; D055114:X-Ray Microtomography
chemical_list: D053523:Amelogenin; C507200:Amelx protein, mouse; D020033:Protein Isoforms
keywords: Ameloblasts; Amelogenin; Enamel; MMP20; Secretory stage