First published online October 10, 2008
Development 135, 2102e (2008)
© The Company of Biologists Limited
Evolution not just by degeneration
Gene duplication is a major source of evolutionary novelty because
paralogous (duplicated) genes can acquire new functions. Paralogous genes are
preserved in the genome mainly through subfunctionalization (the division of
an ancestral function). The duplication-degeneration-complementation (DCC)
model proposes that subfunctionalization occurs when duplicated genes retain
different subsets of regulatory elements (so-called complementary
degeneration). But, on p.
3543, Jarinova and colleagues claim that the DDC model does not
totally explain the evolution of duplicated hoxb5 genes in teleosts.
In zebrafish, the expression patterns of hoxb5a and hoxb5b
suggest that the ancestral hoxb5 gene underwent subfunctionalization.
By comparing the Hoxb5 loci of human, mouse, zebrafish and
Takifugu, the researchers identify conserved non-coding elements
(CNEs) near the zebrafish hoxb5 genes. Analysis of the regulatory
activities of these CNEs individually and collectively in transgenic assays
shows that multiple CNEs are needed to target reporter gene expression to
specific hoxb5a and hoxb5b expression domains. Thus,
complementary degeneration of regulatory elements might not be the only route
to subfunctionalization.

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Related articles in Development:
- Functional resolution of duplicated hoxb5 genes in teleosts
- Olga Jarinova, Gary Hatch, Luc Poitras, Christelle Prudhomme, Magdalena Grzyb, Josée Aubin, Félix-Antoine Bérubé-Simard, Lucie Jeannotte, and Marc Ekker
Development 2008 135: 3543-3553.
[Abstract]
[Full Text]