Lecanda F, Warlow P M, Sheikh S, Furlan F, Steinberg T H, Civitelli R
Divisions of Bone and Mineral and Infectious Diseases, Department of Internal Medicine, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri 63110, USA.
J Cell Biol. 2000 Nov 13;151(4):931-44. doi: 10.1083/jcb.151.4.931.
Connexin(Cx)43 is the major gap junction protein present in osteoblasts. We have shown that overexpression of Cx45 in osteoblasts expressing endogenous Cx43 leads to decreased cell-cell communication (Koval, M., S.T. Geist, E.M. Westphale, A.E. Kemendy, R. Civitelli, E.C. Beyer, and T.H. Steinberg. 1995. J. Cell Biol. 130:987-995) and transcriptional downregulation of several osteoblastic differentiation markers (Lecanda, F., D.A. Towler, K. Ziambaras, S.-L. Cheng, M. Koval, T.H. Steinberg, and R. Civitelli. 1998. Mol. Biol. Cell 9:2249-2258). Here, using the Cx43-null mouse model, we determined whether genetic deficiency of Cx43 affects skeletal development in vivo. Both intramembranous and endochondral ossification of the cranial vault were delayed in the mutant embryos, and cranial bones originating from migratory neural crest cells were also hypoplastic, leaving an open foramen at birth. Cx43-deficient animals also exhibited retarded ossification of the clavicles, ribs, vertebrae, and limbs, demonstrating that skeletal abnormalities are not restricted to a neural crest defect. However, the axial and appendicular skeleton of Cx43-null animals were essentially normal at birth. Cell to cell diffusion of calcein was poor among Cx43-deficient osteoblasts, whose differentiated phenotypic profile and mineralization potential were greatly impaired, compared with wild-type cells. Therefore, in addition to the reported neural crest cell defect, lack of Cx43 also causes a generalized osteoblast dysfunction, leading to delayed mineralization and skull abnormalities. Cell to cell signaling, mediated by Cx43 gap junctions, was critical for normal osteogenesis, craniofacial development, and osteoblastic function.
连接蛋白（Cx）43是成骨细胞中主要的间隙连接蛋白。我们已经表明，在表达内源性Cx43的成骨细胞中过表达Cx45会导致细胞间通讯减少（科瓦尔，M.，S.T. 盖斯特，E.M. 韦斯特法尔，A.E. 凯门迪，R. 奇维泰利，E.C. 拜尔，以及T.H. 斯坦伯格。1995年。《细胞生物学杂志》130:987 - 995）以及几种成骨细胞分化标志物的转录下调（莱坎达，F.，D.A. 陶勒，K. 齐姆巴拉拉斯，S.-L. 程，M. 科瓦尔，T.H. 斯坦伯格，以及R. 奇维泰利。1998年。《分子生物学细胞》9:2249 - 2258）。在此，我们使用Cx43基因敲除小鼠模型，确定Cx43基因缺陷是否在体内影响骨骼发育。突变胚胎中颅顶的膜内成骨和软骨内成骨均延迟，源自迁移神经嵴细胞的颅骨也发育不全，出生时留有一个开放的孔。Cx43基因缺陷的动物还表现出锁骨、肋骨、椎骨和四肢的骨化延迟，表明骨骼异常并不局限于神经嵴缺陷。然而，Cx43基因敲除动物的中轴和附属骨骼在出生时基本正常。与野生型细胞相比，Cx43基因缺陷的成骨细胞中钙黄绿素的细胞间扩散较差，其分化的表型特征和矿化潜能受到极大损害。因此，除了已报道的神经嵴细胞缺陷外，Cx43的缺失还会导致成骨细胞普遍功能障碍，导致矿化延迟和颅骨异常。由Cx43间隙连接介导的细胞间信号传导对于正常的骨生成、颅面发育和成骨细胞功能至关重要。
