Degenerate evolution of the hedgehog gene in a hemichordate lineage

Atsuko Sato, Helen White-Cooper, Karen Doggett, Peter W.H. Holland

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

The discovery of a set of highly conserved genes implicated in patterning during animal development represents one of the most striking findings from the field of evolutionary developmental biology. Existence of these ''developmental toolkit'' genes in diverse taxa, however, does not necessarily imply that they always perform the same functions. Here, we demonstrate functional evolution in a major toolkit gene. hedgehog (hh) encodes a protein that undergoes autocatalytic cleavage, releasing a signaling molecule involved in major developmental processes, notably neural patterning. We find that the hh gene of a colonial pterobranch hemichordate, Rhabdopleura compacts, is expressed in a dramatically different pattern to its ortholog in a harrimaniid entero- pneust hemichordate, Saccoglossus kowalevskii. These represent two of the three major hemichordate lineages, the third being the indirect developing ptychoderid enteropneusts. We also show that the normally well-conserved amino acid sequence of the autoproteolytic cleavage site has a derived change in S. kowalevskii. Using ectopic expression in Drosophila,wefind that this amino acid substitution reduces the efficiency of Hh autocatalytic cleavage and its signaling function. We conclude that the Hh sequence and expression in S. kowalevskii represent the derived state for deuterostomes, and we argue that functional evolution accompanied secondary reduction of the central nervous system in harrimaniids.

Original languageEnglish
Pages (from-to)7491-7494
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number18
DOIs
Publication statusPublished - 2009 May 5

Keywords

  • Autoproteolysis
  • Central nervous system
  • Molecular evolution pterobranch
  • Saccoglossus

ASJC Scopus subject areas

  • General

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