Departments of Biochemistry (W.S., A.Y., R.A., D.S., M.N., R.N., R.K.), Prosthodontics (W.S., K.B.), Periodontology (R.A., M.Y.), and Orthodontics (M.N., R.N., K.M.), School of Dentistry, Showa University, Tokyo 142-8555, Japan; Laboratory of Animal Resources (H.K., T.H., A.A.), Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo 113-0033, Japan; and Department of Physiology and Cell Biology (S.T.), Tokyo Medical and Dental University Graduate School and Faculty of Medicine, Tokyo 101-0062, Japan.
Endocrinology. 2015 Jan;156(1):314-22. doi: 10.1210/en.2014-1032.
Cdc42 is a widely expressed protein that belongs to the family of Rho GTPases and controls a broad variety of signal transduction pathways in a variety of cell types. To investigate the physiological functions of Cdc42 during cartilage development, we generated chondrocyte-specific inactivated Cdc42 mutant mice (Cdc42(fl/fl); Col2-Cre). The gross morphology of mutant neonates showed shorter limbs and body as compared with the control mice (Cdc42(fl/fl)). Skeletal preparations stained with alcian blue and alizarin red also revealed that the body and the long bone length of the mutants were shorter than those of the control mice. Furthermore, severe defects were found in growth plate chondrocytes in the femur sections of mutant mice, characterized by a reduced proliferating zone height, wider hypertrophic zone, and loss of columnar organization in proliferating chondrocytes. The expression levels of chondrocyte marker genes, such as Col2, Col10, and Mmp13, in mutant mice were decreased as compared with the control mice. Mineralization of trabecular bones in the femur sections was also decreased in the mutants as compared with control mice, whereas osteoid volume was increased. Together these results suggested that chondrocyte proliferation and differentiation in growth plates in the present mutant mice were not normally organized, which contributed to abnormal bone formation. We concluded that Cdc42 is essential for cartilage development during endochondral bone formation.
Cdc42 是一种广泛表达的蛋白，属于 Rho GTPase 家族，可调控多种细胞类型中的多种信号转导途径。为了研究 Cdc42 在软骨发育过程中的生理功能，我们生成了软骨细胞特异性失活 Cdc42 突变小鼠（Cdc42(fl/fl); Col2-Cre）。与对照组小鼠（Cdc42(fl/fl)）相比，突变型新生鼠的大体形态表现为四肢和身体更短。用茜素红和阿利新蓝染色的骨骼标本也显示，突变体的身体和长骨长度比对照组小鼠更短。此外，在突变鼠的股骨生长板软骨中发现了严重的缺陷，其特征为增殖区高度降低、肥大区变宽以及增殖软骨细胞的柱状结构丢失。与对照组相比，突变鼠的软骨细胞标志物基因（如 Col2、Col10 和 Mmp13）的表达水平降低。与对照组相比，突变鼠股骨小梁骨的矿化也减少，而类骨质体积增加。这些结果表明，本研究中突变鼠的生长板软骨细胞增殖和分化不能正常组织，这导致了骨形成异常。我们得出结论，Cdc42 对于软骨发育和骺板内骨形成过程是必需的。
