Inst. f. Informatik   
Uni Leipzig

Bioinformatics Preprint 05-006

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The fish specific Hox cluster duplication is coincident with the origin of teleosts

Karen D. Crow, Peter F. Stadler, Vincent J. Lynch, Chris T. Amemiya, Günter P. Wagner


The Hox gene complement of zebrafish, medaka, and fugu differs from that of other gnathostome vertebrates. These fishes have seven to eight Hox clusters compared to the four Hox clusters described in sarcopterygians and shark. The clusters in different teleost lineages are orthologous, implying that a fish specific Hox cluster duplication has occurred in the stem lineage leading to the most recent common ancestor of zebrafish and fugu. The timing of this event, however, is unknown. To address this question, we sequenced four Hox genes from taxa representing basal actinopterygian and teleost lineages, and compared them to known sequences from shark, coelacanth, zebrafish and other teleosts. The resulting gene genealogies suggest that the "fish specific" Hox cluster duplication occurred coincident with the origin of crown group teleosts. In addition, we obtained evidence for an independent Hox cluster duplication in the sturgeon lineage (Acipenseriformes). Finally, results from HoxA11 and HoxB5 suggest that duplicated Hox genes have experienced strong diversifying selection immediately after the duplication event. Taken together, these results support the notion that the duplicated Hox genes of teleosts were causally relevant to adaptive evolution during the initial teleost radiation.

Keywords: Hox cluster, genome duplication, ray-finned fishes, Darwinian selection

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