MMP20 modulates cadherin expression in ameloblasts as enamel develops.
Matrix metalloproteinase-20 (enamelysin, MMP20) is essential for dental enamel development. Seven different MMP20 mutations in humans cause non-syndromic enamel malformations, termed amelogenesis imperfecta, and ablation of Mmp20 in mice results in thin brittle enamel with a dysplastic rod pattern. Healthy enamel formation requires the sliding movement of ameloblasts in rows during the secretory stage of development. This is essential for formation of the characteristic decussating enamel rod pattern observed in rodents, and this is also when MMP20 is secreted into the enamel matrix. Therefore, we propose that MMP20 facilitates ameloblast movement by cleaving ameloblast cell-cell contacts. Here we show that MMP20 cleaves the extracellular domains of the E- and N-cadherin adherens junction proteins, that both E- and N-cadherin transcripts are expressed at significantly higher levels in Mmp20 null vs. wild-type (WT) mice, and that in Mmp20 ablated mice, high-level ameloblast N-cadherin expression persists during the maturation stage of development. Furthermore, we show that E-cadherin gene expression is down-regulated from the pre-secretory to the secretory stage, while N-cadherin levels are up-regulated. This E- to N-cadherin switch supports epithelial migration in other tissues and may be an important event necessary for the ameloblasts to start moving in rows that slide by one another.
Department of Mineralized Tissue Biology and Harvard School of Dental Medicine, The Forsyth Institute, 245 First Street, Cambridge, MA 02142, USA.
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Guan
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Bartlett
D022005:Adherens Junctions / Q000378:metabolism / Q000648:ultrastructure; D000565:Ameloblasts / Q000378:metabolism*; D000566:Amelogenesis / Q000502:physiology*; D000818:Animals; D015820:Cadherins / Q000032:analysis / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D018929:Cell Culture Techniques; D019070:Cell Lineage; D002465:Cell Movement / Q000502:physiology; D003743:Dental Enamel / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D004658:Enamel Organ / Q000166:cytology; D005838:Genotype; D053519:Matrix Metalloproteinase 20 / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000235:genetics
D015820:Cadherins; D053519:Matrix Metalloproteinase 20; C507113:Mmp20 protein, mouse
ameloblast; cadherins; enamel biomineralization/formation; gene expression; junctional complexes; matrix metalloproteinases (MMPs)