Gavaia Paulo J, Simes Dina C, Ortiz-Delgado J B, Viegas Carla S B, Pinto Jorge P, Kelsh Robert N, Sarasquete M Carmen, Cancela M Leonor
CCMAR, Universidade do Algarve, 8005-139 Faro, Portugal.
Gene Expr Patterns. 2006 Aug;6(6):637-52. doi: 10.1016/j.modgep.2005.11.010. Epub 2006 Feb 2.
Bone Gla protein (Bgp or osteocalcin) and matrix Gla protein (Mgp) are important in calcium metabolism and skeletal development, but their precise roles at the molecular level remain poorly understood. Here, we compare the tissue distribution and accumulation of Bgp and Mgp during larval development and in adult tissues of zebrafish (Danio rerio) and throughout metamorphosis in Senegal sole (Solea senegalensis), two fish species with contrasting environmental calcium levels and degrees of skeletal reorganization at metamorphosis. Mineral deposition was investigated in parallel using a modified Alizarin red/Alcian blue protocol allowing sensitive simultaneous detection of bone and cartilage. In zebrafish, bgp and mgp mRNAs were localized in all mineralized tissues during and after calcification including bone and calcified cartilage of branchial arches. Through immunohistochemistry we demonstrated that these proteins accumulate mainly in the matrix of skeletal structures already calcified or under calcification, confirming in situ hybridization results. Interestingly, some accumulation of Bgp was also observed in kidney, possibly due to the presence of a related protein, nephrocalcin. Chromosomal localization of bgp and mgp using a zebrafish radiation hybrid panel indicated that both genes are located on the same chromosome, in contrast to mammals where they map to different chromosomes, albeit in regions showing synteny with the zebrafish location. Results in Senegal sole further indicate that, during metamorphosis, there is an increase in expression of both bgp and mgp, paralleling calcification of axial skeleton structures. In contrast with results obtained for previously studied marine fishes, in zebrafish and Senegal sole Mgp accumulates in both calcified tissues and non-mieralized vessel walls of the vascular system. These results suggest different patterns of Mgp accumulation between fish and mammals.
骨钙素（Bgp或骨钙蛋白）和基质Gla蛋白（Mgp）在钙代谢和骨骼发育中起重要作用，但其在分子水平的确切作用仍知之甚少。在这里，我们比较了斑马鱼（Danio rerio）幼体发育和成年组织以及塞内加尔鳎（Solea senegalensis）整个变态过程中Bgp和Mgp的组织分布和积累情况，这两种鱼类的环境钙水平和变态时骨骼重组程度形成对比。同时使用改良的茜素红/阿尔新蓝方案研究矿物质沉积，该方案能够灵敏地同时检测骨骼和软骨。在斑马鱼中，bgp和mgp mRNA在钙化期间及之后定位于所有矿化组织，包括鳃弓的骨骼和钙化软骨。通过免疫组织化学我们证明这些蛋白质主要积累在已经钙化或正在钙化的骨骼结构基质中，证实了原位杂交结果。有趣的是，在肾脏中也观察到一些Bgp的积累，可能是由于相关蛋白肾钙素的存在。使用斑马鱼辐射杂种细胞系对bgp和mgp进行染色体定位表明，这两个基因位于同一染色体上，这与哺乳动物不同，在哺乳动物中它们定位于不同染色体，尽管在与斑马鱼定位显示同线性的区域。塞内加尔鳎的结果进一步表明，在变态过程中，bgp和mgp的表达均增加，与轴向骨骼结构的钙化平行。与先前研究的海洋鱼类结果相反，在斑马鱼和塞内加尔鳎中，Mgp在钙化组织和血管系统的非矿化血管壁中均有积累。这些结果表明鱼类和哺乳动物之间Mgp积累模式不同。
