The NK homeobox gene cluster predates the origin of Hox genes
The NK homeobox gene cluster predates the origin of Hox genes
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DOI：
10.1016/j.cub.2007.03.008
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发表时间：
2007-04-17
期刊：
影响因子：
9.2
通讯作者：
Degnan, Bernard M.
中科院分区：
文献类型：
--
作者：
Larroux, Claire;Fahey, Bryony;Degnan, Bernard M.
Hox和其他ANTP样同源异型盒基因亚型ParaHox、EHGbox和NK样基因对双侧畸形的关键发育事件有贡献[1-4]。ANTP基因在多个动物基因组中的物理聚类证据[4-9]表明，所有四个亚类都是通过顺序顺式重复事件产生的。在这里，我们表明，Hox基因的起源发生在海绵和真后生动物谱系的分歧，并伴随着动物体平面复杂性的重大进化转变。通过使用全基因组信息demosponge Amphimedon queenslandica，我们提供了第一个确凿的证据，最早的后生动物拥有多个NK样基因，但没有Hox，ParaHox，或EHGbox基因。双齿类基因组中存在的8个NK样基因中的6个在71 kb内以类似于双侧NK簇的顺序聚集。我们推断，NK集群在最后的共同祖先海绵，刺胞动物，bilaterians至少由5个基因。看来ProtoHox基因起源于海绵和真后生动物谱系分化后的这一祖先簇内。维持NK集群在海绵和bilaterians超过5.5亿年，可能反映了固有的监管约束组织这个古老的集群。
Hox and other Antennapedia (ANTP)-like homeobox gene subclasses-ParaHox, EHGbox, and NK-likecontribute to key developmental events in bilaterians [1-4]. Evidence of physical clustering of ANTP genes in multiple animal genomes [4-9] suggests that all four subclasses arose via sequential cis-duplication events. Here, we show that Hox genes'origin occurred after the divergence of sponge and eumetazoan lineages and occurred concomitantly with a major evolutionary transition in animal body-plan complexity. By using whole genome information from the demosponge Amphimedon queenslandica, we provide the first conclusive evidence that the earliest metazoans possessed multiple NK-like genes but no Hox, ParaHox, or EHGbox genes. Six of the eight NK-like genes present in the Amphimedon genome are clustered within 71 kb in an order akin to bilaterian NK clusters. We infer that the NK cluster in the last common ancestor to sponges, cnidarians, and bilaterians consisted of at least five genes. It appears that the ProtoHox gene originated from within this ancestral cluster after the divergence of sponge and eumetazoan lineages. The maintenance of the NK cluster in sponges and bilaterians for greater than 550 million years is likely to reflect regulatory constraints inherent to the organization of this ancient cluster.