Yan Y L, Hatta K, Riggleman B, Postlethwait J H
Institute of Neuroscience, University of Oregon, Eugene 97403, USA.
Dev Dyn. 1995 Jul;203(3):363-76. doi: 10.1002/aja.1002030308.
To understand the hierarchy of developmental controls underlying axis specification in vertebrate embryos, it is helpful to identify relationships between regulatory molecules and the genes that give axial cells their differentiated phenotypes. This work reports the cloning and expression pattern of one of these differentiation genes, a type II collagen (col2a1) gene from the zebrafish Danio rerio. Along the embryonic axis, col2a1 is expressed dynamically in three rows that are each a single cell wide: the notochord and the rows of cells immediately dorsal and ventral to it--the floor plate of the central nervous system, and the hypochord. In addition, col2a1 is expressed in the pharyngeal arches, the epithelium of the otic capsule, and in the mesenchyme of the neurocranium. Experiments probed the expression pattern of col2a1 relative to that of known or potential regulators of axis development, including axial, sonic hedgehog, twist, and cyclops. The results showed that the spatial and temporal pattern of col2a1 expression in axial mesoderm follows the expression of twist closer than other genes tested. In cyclops embryos, which lack an intact floor plate, col2a1 expression was usually low, but not missing in cells in the ventral spinal cord. Because col2a1 expression reveals abnormalities in the notochord of cyclopsb16 embryos, and less col2a1-expressing mesenchyme accumulates rostral to the notochord in cyclops embryos, the effects of the cyclopsb16 mutation are not confined to the central nervous system.
为了理解脊椎动物胚胎中轴特化背后的发育控制层次结构，识别调控分子与赋予轴向细胞分化表型的基因之间的关系很有帮助。这项工作报道了其中一个分化基因的克隆及表达模式，该基因是来自斑马鱼（Danio rerio）的II型胶原蛋白（col2a1）基因。沿着胚胎轴，col2a1在三排细胞中动态表达，每排细胞只有一个细胞宽：脊索以及紧邻其背侧和腹侧的细胞排——中枢神经系统的底板和下索。此外，col2a1在咽弓、耳囊上皮以及神经颅的间充质中表达。实验探究了col2a1相对于已知或潜在的轴发育调节因子（包括axial、sonic hedgehog、twist和cyclops）的表达模式。结果表明，轴向中胚层中col2a1表达的时空模式比其他测试基因更接近twist的表达。在缺乏完整底板的cyclops胚胎中，col2a1表达通常较低，但在腹侧脊髓细胞中并未缺失。由于col2a1表达揭示了cyclopsb16胚胎脊索中的异常，并且在cyclops胚胎中，col2a1表达的间充质在脊索前方积累较少，所以cyclopsb16突变的影响并不局限于中枢神经系统。
