Developmental Genetics of Amphioxus: Insights into the Origin and Evolution of the Vertebrate Body Plan

动物发育背后的分子机制非常相似，这为研究远亲动物之间的身体部位同源性提供了有力的工具。霍兰德博士将脊椎动物与头脊索动物、文文鱼进行了比较，文文鱼在很多方面都接近脊椎动物进化而来的无脊椎动物的身体结构。文昌鱼的发育基因与其他动物的同源基因序列相似，分离鉴定，并将这些基因的表达域作为表征身体部位同源性的表型特征。Hox基因和Engrailed基因确定了文昌鱼后脑的界限，一些基因（如Wnts、Distal-less、PAX7和NK2）被用来绘制文昌鱼前脑和中脑的区域。在脊椎动物的眼睛和文昌鱼的光感受器之间（Pax6），脊椎动物的肾细胞和文昌鱼的肾盂之间（Pax2），以及脊椎动物的甲状腺和文昌鱼的内层之间（Pax8， TTFL）的比较中，也存在类似的原理。此外，致畸剂施用或显微手术后的发育基因表达模式正在确定脊椎动物和文昌鱼共同的表观遗传网络。

The molecular machinery underlying development is remarkably similar among animals, and this provides a powerful tool for suqqesting body part homologies between distantly related animals. Dr. Holland comparing vertebrates with the cephalochordate, amphioxus-which, in many ways, approximates the invertebrate body plan from which the vertebrates evolved. Developmental genes of amphioxus are isolated and identified on the basis of sequence similarities with homologous genes of other animals, and the expression domains of these genes are used as phenotypic characters to indicate body part homologies. Hox genes and Engrailed gene are establishing the limits of the amphioxus hindbrain, and several genes (e.g. Wnts, Distal-less, PAX7, and NK2) are being used to map the regions of the amphioxus forebrain and midbrain. A similar rationale underlies comparison between vertebrate eyes and amphioxus photoreceptors (Pax6), between vertebrate nephrons and amphioxus nephridia (Pax2), and between the vertebrate thyroid and the amphioxus endostyle (Pax8, TTFL). In addition, developmental gene expression patterns after teratogen administration or microsurgery are identifying epigenetic networks common to vertebrates and amphioxus.