Mglinets V A
Genetika. 1995 Mar;31(3):304-14.
The processes of segmentation of axial structures in vertebrates during early embryonic development are reviewed. These processes include the formation of neuromeres, somitomeres, cranial ganglia, and branchial arches in the head and of neuromeres, somites, spinal ganglia, and motor nerves in the body of the embryo. The class of vertebrate homeobox genes Hox is described with respect to the arrangement of these genes in four clusters, the structural and functional similarity of paralogues in gene subfamilies, and the type of Hox gene expression in the head and body. A hypothesis concerning the existence of a genetic Hox code, determining the fate of individual segments in neuroectodermal and mesenchymal derivatives, is discussed. In the context of this hypothesis, phenotypic expression of the mutant Hox genes, accompanied by the loss of their function and cases of excessive and ectopic expression of Hox genes, are analyzed. Only in such cases do mutant phenotypes demonstrate symptoms of actual homeotic transformation, in which specific segmental structures are substituted by their homologues, as has been described for homeotic mutations in Drosophila.
本文综述了脊椎动物早期胚胎发育过程中轴结构的分割过程。这些过程包括头部神经节、体节、颅神经节和鳃弓的形成，以及胚胎身体中神经节、体节、脊髓神经节和运动神经的形成。文中描述了脊椎动物同源框基因Hox家族，包括这些基因在四个基因簇中的排列方式、基因亚家族中旁系同源基因的结构和功能相似性，以及Hox基因在头部和身体中的表达类型。文中还讨论了一种关于存在遗传Hox编码的假说，该假说认为Hox编码决定了神经外胚层和间充质衍生物中各个节段的命运。在此假说的背景下，分析了突变Hox基因的表型表达，包括其功能丧失的情况以及Hox基因过度表达和异位表达的情况。只有在这些情况下，突变表型才会表现出实际同源异型转化的症状，即特定的节段结构被其同源结构所取代，这与果蝇中的同源异型突变情况类似。
