Identical genomic organization of two hemichordate hox clusters.

TitleIdentical genomic organization of two hemichordate hox clusters.
Publication TypeJournal Article
Year of Publication2012
AuthorsFreeman, R, Ikuta, T, Wu, M, Koyanagi, R, Kawashima, T, Tagawa, K, Humphreys, T, Fang, G-C, Fujiyama, A, Saiga, H, Lowe, C, Worley, K, Jenkins, J, Schmutz, J, Kirschner, M, Rokhsar, D, Satoh, N, Gerhart, J
JournalCurr Biol
Date Published2012 Nov 06
KeywordsAnimals, Biological Evolution, Chordata, Nonvertebrate, Genes, Homeobox, Genome, Molecular Sequence Data, Multigene Family, Phylogeny, Transcription, Genetic

Genomic comparisons of chordates, hemichordates, and echinoderms can inform hypotheses for the evolution of these strikingly different phyla from the last common deuterostome ancestor. Because 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 550 kb and 452 kb intervals, respectively. Genes hox1-hox9/10 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 588 kb 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-hox9/10 region, with the number and kind of posterior genes still to be elucidated.

Alternate JournalCurr Biol
PubMed ID23063438
PubMed Central IDPMC4524734
Grant ListR01 HD037277 / HD / NICHD NIH HHS / United States
R01 HD042724 / HD / NICHD NIH HHS / United States
U54 HG003273 / HG / NHGRI NIH HHS / United States

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