Hatakeyama J, Fukumoto S, Nakamura T, Haruyama N, Suzuki S, Hatakeyama Y, Shum L, Gibson C W, Yamada Y, Kulkarni A B
Functional Genomics Section, Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
J Dent Res. 2009 Apr;88(4):318-22. doi: 10.1177/0022034509334749.
Amelogenin and ameloblastin, the major enamel matrix proteins, are important for enamel mineralization. To identify their synergistic roles in enamel development, we generated Amel X(-/-)/Ambn(-/-) mice. These mice showed additional enamel defects in comparison with Amel X(-/-) or Ambn(-/-) mice. In 7-day-old Amel X(-/-)/Ambn(-/-) mice, not only was the ameloblast layer irregular and detached from the enamel surface, as in Ambn(-/-), but also, the enamel width was significantly reduced in the double-null mice as compared with Amel X(-/-) or Ambn(-/-) mice. Proteomic analysis of the double-null teeth revealed increased levels of RhoGDI (Arhgdia), a Rho-family-specific guanine nucleotide dissociation inhibitor, which is involved in important cellular processes, such as cell attachment. Both Amel X(-/-)/Ambn(-/-) mice and Ambn(-/-) mice displayed positive staining with RhoGDI antibody in the irregularly shaped ameloblasts detached from the matrix. Ameloblastin-regulated expression of RhoGDI suggests that Rho-mediated signaling pathway might play a role in enamel formation.
釉原蛋白和成釉蛋白是主要的釉质基质蛋白，对釉质矿化很重要。为了确定它们在釉质发育中的协同作用，我们培育了Amel X(-/-)/Ambn(-/-)小鼠。与Amel X(-/-)或Ambn(-/-)小鼠相比，这些小鼠表现出额外的釉质缺陷。在7日龄的Amel X(-/-)/Ambn(-/-)小鼠中，不仅成釉细胞层不规则且从釉质表面脱离，如同在Ambn(-/-)小鼠中那样，而且与Amel X(-/-)或Ambn(-/-)小鼠相比，双敲除小鼠的釉质宽度显著减小。对双敲除牙齿的蛋白质组分析显示，RhoGDI（Arhgdia）水平升高，RhoGDI是一种Rho家族特异性鸟嘌呤核苷酸解离抑制剂，参与细胞附着等重要细胞过程。在从基质脱离的形状不规则的成釉细胞中，Amel X(-/-)/Ambn(-/-)小鼠和Ambn(-/-)小鼠均显示RhoGDI抗体呈阳性染色。成釉蛋白对RhoGDI表达的调节表明，Rho介导的信号通路可能在釉质形成中发挥作用。
