JTW's Evolutionary Origins - Authors: Amores, A.; Force, A; Yan,Y.L.; Joly, L.; Ameniya, C.; Fritz, A.; Ho, R.K.; Langeland J.; Prince V.; Wang Y.L.; Westerfield, M.; Ekker, M.; Postlesthwai J.H.
HOME
Hox Clusters and Gene Duplications
"HOX cluster genes encode DNA binding proteins that specify fate along the anterior-posterior axis of bilaterian animals. Remarkably, the order of HOX genes along the chromosome reflects the order they act along the body. Invertebrate chordates have one HOX cluster and little axial diversity, but tetrapods have four clusters and substantial axial complexity. Tetrapod clusters arose by duplications of an ancestral cluster containing 13 genes. Although it is widely assumed that vertebrates have four HOX clusters, initial studies of teleost fish, the most diverse group of vertebrates, revealed unexpected HOX genes [for instance some teleosts, like the zebrafish Danio rerio, have seven HOX clusters]"(Amores et al, 1998)
"Hence, the duplication events that produced the four mammalian clusters occurred before the divergence of ray-finned and lobe-finned lineages about 420 million years ago."
(Amores et al, 1998)
"These data suggest that all hox clusters duplicated in the lineage that led to zebrafish after it diverged from the lineage that led to tetrapods, with subsequent loss of one hoxd cluster."
(Amores et al, 1998)
"Comparative analysis of cluster content illuminates the history of HOX cluster duplication. The (AB)(CD) model suggests two sequential duplications, giving a proto-AB cluster and a proto-CD cluster after the first event. The alternative (D(A(BC))) model suggests three duplications, the first producing the D and proto-ABC clusters, the second giving the A and proto-BC clusters, and the third providing the B and C clusters. Cladistic analysis of cluster content favors the (AB)(CD) model. For example, loss of group 12 is a shared derived characteristic of teleost and tetrapod HOXA and HOXB clusters, and loss of groups 2 and 7 unites HOXC and HOXD clusters. This model minimizes the number of convergent gene losses and is also independently supported by sequence analysis."
(Amores et al, 1998)
"The conclusion that the genetic complexity of hox clusters in teleost fish has exceeded that of mammals for more than 100 million years calls into question the concept of a tight linkage of HOX cluster number and morphological complexity along the body axis. However, because teleosts are the most species-rich group of vertebrates and exhibit tremendous morphological diversity, it is tempting to speculate that the duplication event detected here may have provided gene copies that helped spur the teleost radiation."
(Amores et al, 1998)
- Amores, A.; Force, A; Yan,Y.L.; Joly, L.; Ameniya, C.; Fritz, A.; Ho, R.K.; Langeland J.; Prince V.; Wang Y.L.; Westerfield, M.; Ekker, M.; Postlesthwai J.H.
- Zebrafish Hox Clusters and Vertebrate Genome Evolution
- Science: Vol. 282, No. 5394, pp. 1711-1714
- November 27, 1998
- [Pubmed]
HOME