The NK Homeobox Gene Cluster Predates the Origin of Hox Genes

Hox and other Antennapedia (ANTP)-like homeobox gene subclasses—ParaHox, EHGbox, and NK-like—contribute 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-duplicat...

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Bibliographic Details
Published in:Current biology 2007-04, Vol.17 (8), p.706-710
Main Authors: Larroux, Claire, Fahey, Bryony, Degnan, Sandie M., Adamski, Marcin, Rokhsar, Daniel S., Degnan, Bernard M.
Format: Article
Language:English
Subjects:
Amphimedon
Animals
Antennapedia Homeodomain Protein - genetics
Bilateria
Cnidaria - genetics
DNA, Complementary
Embryo, Nonmammalian - chemistry
EVO_ECOL
Evolution, Molecular
Gastropoda - genetics
Genes, Homeobox
Genome
Invertebrates - genetics
Metazoa
Multigene Family
Porifera - genetics
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Summary:Hox and other Antennapedia (ANTP)-like homeobox gene subclasses—ParaHox, EHGbox, and NK-like—contribute 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.
ISSN:0960-9822
1879-0445
DOI:10.1016/j.cub.2007.03.008