Evolution Diary

Spiny creature’s genome insight
By Molly Bentley

Scientists have unravelled the genetic code of the sea urchin, an animal whose evolutionary lineage may be key to understanding the relationship of humans and other vertebrates to invertebrates.

Analysis of the genome of the male California purple sea urchin ( Strongylocentrotus purpuratus ) has revealed many genes previously thought unique to vertebrates, along with an innovative immune system and a surprising array of sensory proteins.

“This was a big payoff genome,” said Eric Davidson from the California Institute of Technology (Caltech).

“It is the first time in a while that a genome has been sequenced that’s not closely related to another genome that’s already been sequenced,” explained the molecular biologist who was closely involved with the sequencing project, along with researchers at the Human Genome Sequencing Center (HGSC) at Baylor College of Medicine in Houston.

The results, appearing this week in the journal Science, with more than 40 more papers to follow in the December issue of Developmental Biology, are the culmination of three years of work by an international team of 240 scientists.

It turns out that the sea urchin is very much like us
Dr George Weinstock, HGSC

The group estimates the sea urchin has 23,300 genes. For comparison, the fruit fly has about 13,600 and humans 20,000 to 25,000.

“Any snorkeler who has ever marvelled at the spherical, almost otherworldly, symmetry of the sea urchin will be amazed to learn that this organism, so different in habitat and body plan from ourselves, actually shares a substantial number of the same genes and pathways,” said Francis Collins, director of the National Human Genome Research Institute (NHGRI) which helped fund the project.

“It turns out that the sea urchin is very much like us,” said George Weinstock, the co- director of the HGSC. “You wouldn’t think it to look at it. But it’s closer to us than a fly,” he said.

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