A basal deuterostome genome viewed as a natural experiment.pdfVIP

Available online at Gene 406 (2007) 1 – 7 /locate/gene Review A basal deuterostome genome viewed as a natural experiment R. Andrew Cameron ?, Eric H. Davidson Beckman Institute 139-74, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, United States Received 12 February 2007; received in revised form 26 April 2007; accepted 26 April 2007 Available online 6 May 2007 Abstract With the determination of its genome sequence the utility of the sea urchin model system increases. The phylogenetic position of the sea urchin among the deuterostomes allows for informative comparisons to vertebrate research models. A combined whole genome shotgun and bacterial artificial chromosome based strategy yielded a high quality draft genome sequence of 814 Mb. The predicted gene set estimated to include 23,300 genes was annotated and compared to those of other metazoan animals. Gene family expansions in the innate immune system are large and offer a first glimpse of how the long-lived sea urchin defends itself. The gene sets of the sea urchin place it firmly among the deuterostomes and indicate that various gene family-specific expansions and contractions characterize the evolution of animal genomes rather than the invention of new genes. ? 2007 Elsevier B.V. All rights reserved. Keywords: Evolution; Gene sets; Gene homology 1. Introduction Bilaterian animals that live in the ocean display an enormous amount of morphological and physiological variation. Their genomes embody the historical results of adaptation to specific living conditions that they and their ancestors have encountered over the more than one half billion years of existence on the planet. Thus the individual modern species that result from these various histories are “natural experiments” in that they reflect an accumulation of the successful properties on which natural selection has acted. There is subsequently a wide range of relatively simple biological systems in which particularly s