Exploiting genomics in evolutionary developmental biology

Genomics is providing a new stimulus to research in developmental biology. Here we describe how genomic approaches are giving new insight into the genetic basis for two major developmental transitions in evolution: the origin of vertebrates and the origin of multicellular animals. Our first approach uses complete genome sequences. We compared orthologue group complexity (an estimate of gene family size) between human, fruitfly, nematode and yeast genomes. These analyses suggest extensive gene duplication somewhere on the deuterostome lineage leading to humans. We show that similar events did not occur on the lineages leading to flies or to nematodes. To determine the timing of this event, we then incorporate gene sampling data from a cephalochordate, amphioxus. Molecular phylogenetic analysis of amphioxus genes reveals that gene duplications occurred close to vertebrate origins, coincident with a major developmental transition. By contrast, whole genome comparison between invertebrates and yeast did not reveal a similar event during the origin of multicellular animals. In this case, an EST survey of choanoflagellates is being used to identify genetic changes coincident with animal origins. (C) 2002 Elsevier Science B.V. All rights reserved.