Developmental mechanisms and evolution of vertebrate masticatory systems

结合实验胚胎学、比较胚胎学和分子生物学，对脊椎动物下颚和舌头结构的发育机制和进化进行了研究。通过对中华鲟、鲨鱼和陆虎的正常发育模式的观察，表明齿颌目和齿颌目在早期胚胎模式中基本形态结构是保守的。特别是，中胚层结构表明，agnathans在导致舌头形成的鳃下系统的发育程序中处于低水平。然而，在外胚层和外间充质的特定部位之间的地形关系中，在鼻基板和垂体基板的位置上发现了微小的差异。这种差异与Fgf8基因初始表达域的位置有关。后者基因的表达与下颌弓外切间充质的形成有关。通过局部应用生长因子浸透的微球，我们可以证明，在阶段和发育环境依赖的方式下，颅面外切间质可以被修复。因此，上皮-间充质相互作用在颅面外间充质的初始形成中起着重要作用。扩展这一概念，我们将同样的技术应用于七鳃鳗胚胎，并表明通过组织相互作用的重新模式获得了颌口

Combining the experimental embryology, comparative embryology, and molecular biology, developmental mechanisms and evolution of the vertebrate jaw and tongue structures were investigated. By observing normal developmental patterns of sturgeons, shark, and the lanmprey, it was shown that basic morphological architecture was conserved in early embryonic patterns between gnathostome and agnathan species. Especially, mesodermal configuration has shown that agnathans were at low level of developmental programing of the hypobranchial system that leads to the tongue formation. In the topographical relation between specific parts of the ectoderm and ectomesenchyme, however, a small differerence was detected with regard to the positions of nasal and hypophysial placodes. This difference involved the positions of initial Fgf8 gene expression domain. The lattter gene expression is responsible for the patterning of mandibular arch ectomesenchyme. By local application of growth factor-soaked beads, we could show that in a stage-, and developmental context-dependent manner, the craniofacial ectomesenchyme can be repattened. Thus, epithelial-mesenchymal interactions play fundamental roles in initial shaping of the craniofacial ectomesenchyme. Expanding this concept, we applied the same technique to the lamprey embryo and shoed that the gnathostome jaw was obtained through repatterning of tissue interaction