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First published online 15 October 2003
doi: 10.1242/dev.00811

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Development 130, 5903-5914 (2003)
Copyright © 2003 The Company of Biologists Limited

The amphioxus Hairy family: differential fate after duplication

Carolina Minguillón1,*, Senda Jiménez-Delgado1, Georgia Panopoulou2 and Jordi Garcia-Fernàndez1,{dagger}

1 Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Avenida Diagonal 645, E-08028 Barcelona, Spain
2 Evolution and Development Group, Depart. Prof. Hans Lehrach, Max-Planck-Institut fur Molekulare Genetik, 14195 Berlin (Dahlem), Germany

{dagger} Author for correspondence (e-mail: jgarcia{at}bio.ub.es)

Accepted 21 August 2003

Vertebrate Hairy genes are highly pleiotropic and have been implicated in numerous functions, such as somitogenesis, neurogenesis and endocrine tissue development. In order to gain insight into the timing of acquisition of these roles by the Hairy subfamily, we have cloned and studied the expression pattern of the Hairy gene(s) in amphioxus. The cephalochordate amphioxus is widely believed to be the living invertebrate more closely related to vertebrates, the genome of which has not undergone the massive gene duplications that took place early during vertebrate evolution. Surprisingly, we have isolated eight Hairy genes from the `pre-duplicative' amphioxus genome. In situ hybridisation on amphioxus embryos showed that Hairy genes had experienced a process of subfunctionalisation that is predicted in the DDC model (for duplication-degeneration-complementation). Only the summation of four out of the eight Amphi-Hairy genes expression resembles the expression pattern of vertebrate Hairy genes, i.e. in the central nervous system, presomitic mesoderm, somites, notochord and gut. In addition, Amphi-Hairy genes expression suggest that amphioxus early somites are molecularly prefigured in an anteroposterior sequence in the dorsolateral wall of the archenteron, and the presence of a midbrain/hindbrain boundary. The expansion of the amphioxus Hairy subfamily request for caution when deducing the evolutionary history of a gene family in chordates based in the singularity of the amphioxus genome. Amphioxus may resemble the ancestor of the vertebrates, but it is not the ancestor, only its closest living relative, a privileged position that should not assume the freezing of its genome.

Key words: Hairy, bHLH, amphioxus, DDC model, Subfunctionalisation, Duplication






© The Company of Biologists Ltd 2003