Why Sequence the Sea Squirt?

The Ciona intestinalis genome is the smallest of any experimentally manipulable chordate (organism with a spinal cord). This organism provides a good system for exploring the evolutionary origins of the chordate lineage, from which all vertebrates sprouted. The animal's genome shows many similarities with the human and mouse genomes. Though containing only 15,000-16,000 protein-coding genes--half the size of the human genome--the Ciona genome contains genes similar to human genes that code for hormones and for components of the human immune system and nervous system. About 80 percent of Ciona's genes are also found in humans and other vertebrates. Comparison of the Ciona genome with the genomes of other animals also provides clues to the evolutionary origins of the human brain, spine, heart, eye and thyroid gland.

Ciona's 15,000-plus genes may be controlled by some 10,000 regulatory DNAs, including enhancers and silencers. The complete C. intestinalis genome sequence will provide a foundation for genome-scale analysis of regulatory networks through development.

C. intestinalis has a good genomic infrastructure (EST and cDNA collections, BAC and cosmid libraries, etc.), easily visualized cells and morphogenetic processes, and existing methods for transient transgene expression; and it is available throughout the world all year long. In addition, there is a deep classical literature on sea squirt development and an active community of researchers worldwide.

Genome Portal site: Ciona intestinalis