Null mutation of chloride channel 7 (Clcn7) impairs dental root formation but does not affect enamel mineralization.
ClC-7, located in late endosomes and lysosomes, is critical for the function of osteoclasts. Secretion of Cl(-) by the ruffled border of osteoclasts enables H(+) secretion by v-H(+)-ATPases to dissolve bone mineral. Mice lacking ClC-7 show altered lysosomal function that leads to severe lysosomal storage. Maturation ameloblasts are epithelial cells with a ruffled border that secrete Cl(-) as well as endocytose and digest large quantities of enamel matrix proteins during formation of dental enamel. We tested the hypothesis that ClC-7 in maturation ameloblasts is required for intracellular digestion of matrix fragments to complete enamel mineralization. Craniofacial bones and developing teeth in Clcn7(-/-) mice were examined by micro-CT, immunohistochemistry, quantified histomorphometry and electron microscopy. Osteoclasts and ameloblasts in wild-type mice stained intensely with anti-ClC-7 antibody but not in Clcn7(-/-) mice. Craniofacial bones in Clcn7(-/-) mice were severely osteopetrotic and contained 1.4- to 1.6-fold more bone volume, which was less mineralized than the wild-type littermates. In Clcn7(-/-) mice maturation ameloblasts and osteoclasts highly expressed Ae2 as in wild-type mice. However, teeth failed to erupt, incisors were much shorter and roots were disfigured. Molars formed a normal dental crown. In compacted teeth, dentin was slightly less mineralized, enamel did not retain a matrix and mineralized fairly normal. We concluded that ClC-7 is essential for osteoclasts to resorb craniofacial bones to enable tooth eruption and root development. Disruption of Clcn7 reduces bone and dentin mineral density but does not affect enamel mineralization.
Department Oral Cell Biology, Academic Center of Dentistry Amsterdam (ACTA), University of Amsterdam and VU-University of Amsterdam, MOVE Research Institute, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands. j.guo@acta.nl.|School of Stomatology/Dental Clinic, Zhejiang Chinese Medical University, Mailbox 97, Binwen Road 548, Binjiang District, 310053, Hangzhou, China. j.guo@acta.nl.
Jing
J
Guo
Department Oral Cell Biology, Academic Center of Dentistry Amsterdam (ACTA), University of Amsterdam and VU-University of Amsterdam, MOVE Research Institute, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands.
Theodore J M
TJ
Bervoets
Nordic Bioscience Biomarkers and Research A/S, Hovedgade 207, 2730, Herlev, Denmark.
Kim
K
Henriksen
Department Oral Cell Biology, Academic Center of Dentistry Amsterdam (ACTA), University of Amsterdam and VU-University of Amsterdam, MOVE Research Institute, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands.
Vincent
V
Everts
Department Oral Cell Biology, Academic Center of Dentistry Amsterdam (ACTA), University of Amsterdam and VU-University of Amsterdam, MOVE Research Institute, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands.
Antonius L J J
AL
Bronckers
D000565:Ameloblasts / Q000378:metabolism; D000818:Animals; D015519:Bone Density; D016723:Bone Remodeling; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D002113:Calcification, Physiologic; D018118:Chloride Channels / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism; D003743:Dental Enamel / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics*; D010010:Osteoclasts / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D014092:Tooth Root / Q000473:pathology*; D055114:X-Ray Microtomography
D018118:Chloride Channels; D027963:Chloride-Bicarbonate Antiporters; C490803:Clcn7 protein, mouse
Ameloblasts; ClC-7; Histomorphometry; Immunostaining; Micro-CT; Tooth eruption