Identical genomic organization of two hemichordate hox clusters.
Identical genomic organization of two hemichordate hox clusters.
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DOI：
10.1016/j.cub.2012.08.052
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发表时间：
2012-11-06
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影响因子：
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通讯作者：
Gerhart J
中科院分区：
文献类型：
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作者：
Freeman R;Ikuta T;Wu M;Koyanagi R;Kawashima T;Tagawa K;Humphreys T;Fang GC;Fujiyama A;Saiga H;Lowe C;Worley K;Jenkins J;Schmutz J;Kirschner M;Rokhsar D;Satoh N;Gerhart J
脊索动物、半索动物和棘皮动物的基因组比较可以为这些与最后共同的后口动物祖先截然不同的门的进化假设提供信息。由于 Hox 基因在两侧对称动物中发挥着关键的发育作用，我们分析了两个半索动物基因组的 Hox 复合体。我们发现Saccoglossus kowalevskii和Ptychodera flava都拥有12个基因簇，其中mir10位于hox4和hox5之间，间隔分别为550kb和452kb。簇中的基因 hox1-9 与脊索动物中的直向同源基因具有相同的基因组顺序和转录方向，其中 hox1 位于簇的 3' 端。在 5' 端，每个簇包含三个 Ambulacria（半索动物-棘皮动物进化枝）特有的后部基因，其中两个形成倒置的末端对。相比之下，棘皮动物 Strongylocentrotus purpuratus 包含一个 588kb 的簇，由 11 个半索动物基因的直系同源物组成，顺序不同，似乎反映了祖先半索动物样走行动物簇的重排。脊椎动物的 Hox 簇和基底脊索动物文昌鱼具有与半索动物簇相似的组织，但具有不同的后部基因。这些结果为后口动物祖先中 hox1-9/10 区域的有序复合体提供了基因组证据，但后部基因的数量和种类仍有待阐明。
Genomic comparisons of chordates, hemichordates, and echinoderms can inform hypotheses for the evolution of these strikingly different phyla from the last common deuterostome ancestor. Since hox genes play pivotal developmental roles in bilaterian animals, we analyzed the Hox complexes of two hemichordate genomes. We find that Saccoglossus kowalevskii and Ptychodera flava both possess 12-gene clusters, with mir10 between hox4 and hox5, in 550kb and 452kb intervals, respectively. Genes hox1-9 of the clusters are in the same genomic order and transcriptional orientation as their orthologs in chordates, with hox1 at the 3′ end of the cluster. At the 5′ end, each cluster contains three posterior genes specific to Ambulacraria (the hemichordate-echinoderm clade), two forming an inverted terminal pair. In contrast, the echinoderm Strongylocentrotus purpuratus contains a 588kb cluster of 11 orthologs of the hemichordate genes, ordered differently, plausibly reflecting rearrangements of an ancestral hemichordate-like ambulacrarian cluster. Hox clusters of vertebrates and the basal chordate amphioxus have similar organization to the hemichordate cluster, but with different posterior genes. These results provide genomic evidence for a well-ordered complex in the deuterostome ancestor for the hox1-9/10 region, with the number and kind of posterior genes still to be elucidated.