Johnson Lisa, Ganss Bernhard, Wang Andrew, Zirngibl Ralph A, Johnson Danielle E, Owen Celeste, Bradley Grace, Voronov Irina
Faculty of Dentistry, Department of Oral Pathology, University of Toronto, Toronto, Ontario, Canada.
Faculty of Dentistry, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada.
J Cell Biochem. 2017 Oct;118(10):3328-3340. doi: 10.1002/jcb.25986. Epub 2017 May 3.
Vacuolar H -ATPases (V-ATPases) are ubiquitous multisubunit proton pumps responsible for organellar pH maintenance. Mutations in the a3 subunit of V-ATPases cause autosomal recessive osteopetrosis, a rare disease due to impaired bone resorption. Patients with osteopetrosis also display dental anomalies, such as enamel defects; however, it is not clear whether these enamel abnormalities are a direct consequence of the a3 mutations. We investigated enamel mineralization, spatiotemporal expression of enamel matrix proteins and the a3 protein during tooth development using an osteopetrotic mouse model with a R740S point mutation in the V-ATPase a3 subunit. Histology revealed aberrations in both crown and root development, whereas SEM analysis demonstrated delayed enamel mineralization in homozygous animals. Enamel thickness and mineralization were significantly decreased in homozygous mice as determined by μCT analysis. The expression patterns of the enamel matrix proteins amelogenin, amelotin, and odontogenic ameloblast-associated protein (ODAM) suggested a delay in transition to the maturation stage in homozygous animals. Protein expression of the a3 subunit was detected in ameloblasts in all three genotypes, suggesting that a3-containing V-ATPases play a direct role in amelogenesis, and mutations in a3 delay transition from the secretory to the maturation stage, resulting in hypomineralized and hypoplastic enamel. J. Cell. Biochem. 118: 3328-3340, 2017. © 2017 Wiley Periodicals, Inc.
液泡型H⁺-ATP酶（V-ATP酶）是普遍存在的多亚基质子泵，负责维持细胞器的pH值。V-ATP酶a3亚基的突变会导致常染色体隐性遗传性骨硬化症，这是一种因骨吸收受损而引发的罕见疾病。患有骨硬化症的患者还会出现牙齿异常，如牙釉质缺陷；然而，尚不清楚这些牙釉质异常是否是a3突变的直接后果。我们使用在V-ATP酶a3亚基中存在R740S点突变的骨硬化症小鼠模型，研究了牙齿发育过程中牙釉质矿化、牙釉质基质蛋白和a3蛋白的时空表达。组织学检查显示牙冠和牙根发育均存在异常，而扫描电子显微镜分析表明纯合子动物的牙釉质矿化延迟。通过显微计算机断层扫描分析确定，纯合子小鼠的牙釉质厚度和矿化程度显著降低。牙釉质基质蛋白釉原蛋白、釉成熟蛋白和牙源性成釉细胞相关蛋白（ODAM）的表达模式表明，纯合子动物向成熟阶段的转变延迟。在所有三种基因型的成釉细胞中均检测到了a3亚基的蛋白表达，这表明含a3的V-ATP酶在釉质形成过程中发挥直接作用，a3突变会延迟从分泌阶段到成熟阶段的转变，从而导致牙釉质矿化不足和发育不全。《细胞生物化学杂志》2017年第118卷：3328 - 3340页。© 2017威利期刊公司。
