MBE Advance Access published online on September 25, 2007
Molecular Biology and Evolution, doi:10.1093/molbev/msm194
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Research Article |
A Degenerate ParaHox Gene Cluster in a Degenerate Vertebrate
Department of Zoology, Oxford University, South Parks Road, Oxford OX1 3PS, UK
1 Department of Zoology, Oxford University, South Parks Road, Oxford OX1 3PS, UK
2 Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
3 MPI Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin-Dahlem, Germany
4 Royal Swedish Academy of Sciences, Kristineberg Marine Research Station, Kristineberg 2130, Sweden
Corresponding author: Rebecca F. Furlong Department of Zoology, Oxford University, South Parks Road, Oxford OX1 3PS, UK, rebecca.furlong{at}zoo.ox.ac.uk, tel +44 (0)1865 281090, fax +44 (0), 1865-271184
Received for publication July 23, 2007. Revision received September 3, 2007. Revision received September 5, 2007. Accepted for publication September 7, 2007.
The ParaHox genes consist of three homeobox gene families, Gsx, Xlox and Cdx, all of which have fundamental roles in development. Xlox (known as IPF1 or PDX1 in vertebrates), for example, is crucial for development of the vertebrate pancreas and is also involved in regulation of insulin expression. The invertebrate amphioxus has a gene cluster containing one gene from each of the gene families, while in all vertebrates examined to date there are additional copies resultant from ParaHox gene cluster duplications at the base of the vertebrate lineage. Extant vertebrates basal to bony and cartilaginous fish are central to the question of when and how these multiple genes arose in the vertebrate genome. Here we report the mapping of a ParaHox gene cluster in two species of hagfishes. Unexpectedly, these basal vertebrates have lost a functional Xlox gene from this cluster, unlike every other vertebrate examined to date. Furthermore, our phylogenetic analyses suggest that hagfishes may have diverged from the vertebrate lineage before the duplications which created the multiple ParaHox clusters in jawed vertebrates.
Key Words: ParaHox • 2R • Genome evolution • Hagfish
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