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

动物之间发育的分子机制非常相似，这为确定远亲动物之间的身体部位同源性提供了一个强有力的工具。霍兰德将脊椎动物与头脊椎动物文昌鱼进行了比较，文昌鱼在许多方面与脊椎动物进化而来的无脊椎动物的身体结构相似。文昌鱼的发育基因是在与其他动物同源基因序列相似性的基础上分离和鉴定的，并以这些基因的表达结构域作为表型特征来指示身体部位的同源性。Hox基因和Engraded基因正在确定文昌鱼后脑的界限，几个基因(如Wnts、Distal-less、PAX7和NK2)正被用于定位文昌鱼前脑和中脑的区域。脊椎动物的眼睛和文昌鱼的光感受器(Pax6)，脊椎动物的肾脏和文昌鱼的肾脏(Pax2)，以及脊椎动物的甲状腺和文昌鱼的内花柱(Pax8，TTFL)之间的比较也有类似的理论基础。此外，在给予致畸剂或显微手术后的发育基因表达模式正在识别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.