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WASHINGTON - Sea urchins may be blind but they have the same genes that help people see as well as genes for a sense of smell and one of the most complicated immune systems in the animal world, researchers say.
According to the latest issue of Science, sea
urchins also have genes associated with diseases such as Huntington's and muscular dystrophy, offering new routes to understanding illnesses.
The sea urchin - a pincushion-shaped animal found at the bottom of the sea - shares more than 7000 genes with humans.
It was long known to be more closely related to humans and other vertebrates than other creatures favoured by biologists for research, such as fruit flies and C. elegans roundworms. Comparing human genes with those of other species can help scientists figure out why they evolved and find ways to help when things go wrong.
The studies published in Science confirm this relationship and also make some surprising findings, such as genes for sight found at the bottom of their feet.
"I've been looking at these organisms for 31 years and now I know they were looking back at me," said Gary Wessel, a biology professor at Brown University in Rhode Island.
"We've already learned an enormous amount from the sea urchin, from something as basic as how identical twins form to in-vitro fertilisation procedures.
"With a complete map of the urchin's DNA, we can now learn more quickly and easily how each process works during development."
The team of researchers, led by George Weinstock, of Baylor College of Medicine, studied Strongylocentrotus purpuratus - the California purple sea urchin.
They found that the urchin has about 979 genes for proteins that sense light and odours - similar to what is found in vertebrates that actually do see and smell things. How the sea urchin uses them is not yet clear.
Also remarkable was the animal's immune system, said immunologist Jonathan Rast of the University of Toronto.
Dr Rast hopes the sea urchin's immune system will help in understanding how the human immune system evolved.
Like people, sea urchins have many immune genes that are active in the gut, which may help in coping with symbiotic bacteria that help digest food.
"It is one thing to be able to recognise all bacteria and get rid of them. It is another thing to maintain that in a complex way so you don't kill all of them," Dr Rast said.
Vertebrates have adaptive immune systems as well as innate immune systems that attack invaders without necessarily recognising them, but invertebrates do not.
The study shows sea urchins appear to have the genetic predecessors to the adaptive immune system - the antibodies and T-cells that can change and respond to new germs.
- REUTERS
