Williams N A, Holland P W
School of Animal and Microbial Sciences, University of Reading, U.K.
Mol Biol Evol. 1998 May;15(5):600-7. doi: 10.1093/oxfordjournals.molbev.a025961.
We report the genomic organization and deduced protein sequence of a cephalochordate member of the Otx homeobox gene family (AmphiOtx) and show its probable single-copy state in the genome. We also present molecular phylogenetic analysis indicating that there was single ancestral Otx gene in the first chordates which was duplicated in the vertebrate lineage after it had split from the lineage leading to the cephalochordates. Duplication of a C-terminal protein domain has occurred specifically in the vertebrate lineage, strengthening the case for a single Otx gene in an ancestral chordate whose gene structure has been retained in an extant cephalochordate. Comparative analysis of protein sequences and published gene expression patterns suggest that the ancestral chordate Otx gene had roles in patterning the anterior mesendoderm and central nervous system. These roles were elaborated following Otx gene duplication in vertebrates, accompanied by regulatory and structural divergence, particularly of Otx1 descendant genes.
我们报告了头索动物中Otx同源框基因家族成员（AmphiOtx）的基因组结构和推导的蛋白质序列，并展示了其在基因组中可能的单拷贝状态。我们还进行了分子系统发育分析，结果表明在第一批脊索动物中存在单个祖先Otx基因，该基因在脊椎动物谱系从通向头索动物的谱系中分化出来后发生了复制。C末端蛋白质结构域的复制专门发生在脊椎动物谱系中，这进一步证明了在祖先脊索动物中存在单个Otx基因，其基因结构在现存的头索动物中得以保留。蛋白质序列和已发表的基因表达模式的比较分析表明，祖先脊索动物的Otx基因在塑造前中胚层和中枢神经系统方面发挥作用。在脊椎动物中Otx基因复制后，这些作用得到了进一步发展，同时伴随着调控和结构上的分歧，特别是Otx1后代基因。
