Burke A C, Nelson C E, Morgan B A, Tabin C
Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
Development. 1995 Feb;121(2):333-46. doi: 10.1242/dev.121.2.333.
A common form of evolutionary variation between vertebrate taxa is the different numbers of segments that contribute to various regions of the anterior-posterior axis; cervical vertebrae, thoracic vertebrae, etc. The term 'transposition' is used to describe this phenomenon. Genetic experiments with homeotic genes in mice have demonstrated that Hox genes are in part responsible for the specification of segmental identity along the anterior-posterior axis, and it has been proposed that an axial Hox code determines the morphology of individual vertebrae (Kessel, M. and Gruss, P. (1990) Science 249, 347-379). This paper presents a comparative study of the developmental patterns of homeobox gene expression and developmental morphology between animals that have homologous regulatory genes but different morphologies. The axial expression boundaries of 23 Hox genes were examined in the paraxial mesoderm of chick, and 16 in mouse embryos by in situ hybridization and immunolocalization techniques. Hox gene anterior expression boundaries were found to be transposed in concert with morphological boundaries. This data contributes a mechanistic level to the assumed homology of these regions in vertebrates. The recognition of mechanistic homology supports the historical homology of basic patterning mechanisms between all organisms that share these genes.
脊椎动物类群之间进化变异的一种常见形式是，构成前后轴不同区域的体节数量不同，如颈椎、胸椎等。“转位”一词用于描述这种现象。对小鼠同源异型基因进行的遗传学实验表明，Hox基因在一定程度上负责沿前后轴确定体节特征，并且有人提出，一种轴向Hox编码决定了单个椎骨的形态（凯塞尔，M.和格鲁斯，P.（1990年）《科学》249卷，347 - 379页）。本文对具有同源调控基因但形态不同的动物之间的同源框基因表达发育模式和发育形态进行了比较研究。通过原位杂交和免疫定位技术，在鸡胚的体节中胚层检测了23个Hox基因的轴向表达边界，在小鼠胚胎中检测了16个。发现Hox基因的前表达边界与形态边界协同转位。该数据为脊椎动物这些区域假定的同源性提供了一个机制层面的依据。对机制同源性的认识支持了所有共享这些基因的生物之间基本模式形成机制的历史同源性。
