Fjose A, Molven A, Eiken H G
Laboratory of Biotechnology, University of Bergen, Norway.
Gene. 1988;62(1):141-52. doi: 10.1016/0378-1119(88)90588-4.
As the most primitive group among vertebrates, fish might serve as a model system when studying the genetic regulation of embryogenesis in higher animals. To identify genes important for early development, we have constructed a genomic library from Atlantic salmon (Salmo salar) and screened it with homeobox-containing probes from Drosophila melanogaster. Five different salmon homeoboxes were isolated. Two of these were located in the same clone, separated by only 7.5 kb. This demonstrates the presence of clustered homeobox genes in fish. The two clustered homeoboxes were sequenced and shown to be closely related to the ANT-C/BX-C class of Drosophila, being about 80% homologous to the Ultrabithorax gene (Ubx) homeobox. One of the clustered genes appears to be the salmon equivalent of the mouse Hox-2.1 gene, indicating that some of the vertebrate homeobox-containing genes are conserved in evolution. A more diverged homeobox that shares only 60% homology with Ubx, was also sequenced. In analogy to Drosophila, therefore, the salmon genome contains more than one class of homeoboxes. In addition, Northern-blot experiments demonstrated that two of the homeobox genes are expressed in salmon embryos, suggesting their importance for proper development.
作为脊椎动物中最原始的类群，鱼类可作为研究高等动物胚胎发生遗传调控的模型系统。为了鉴定对早期发育重要的基因，我们构建了大西洋鲑（Salmo salar）的基因组文库，并用来自黑腹果蝇的含同源异型框的探针进行筛选。分离出了5种不同的鲑鱼同源异型框。其中两种位于同一个克隆中，仅相隔7.5 kb。这证明了鱼类中存在成簇的同源异型框基因。对这两个成簇的同源异型框进行了测序，结果表明它们与果蝇的ANT-C/BX-C类密切相关，与超双胸基因（Ubx）的同源异型框约有80%的同源性。其中一个成簇基因似乎是小鼠Hox-2.1基因在鲑鱼中的对应物，这表明一些含同源异型框的脊椎动物基因在进化过程中是保守的。还对一个与Ubx同源性仅为60%的差异更大的同源异型框进行了测序。因此，与果蝇类似，鲑鱼基因组包含不止一类同源异型框。此外，Northern杂交实验表明，其中两个同源异型框基因在鲑鱼胚胎中表达，这表明它们对正常发育很重要。
