An extra eye

Published: Monday 15 November 1999

A valuable lesson for biologists about evolution comes from frogs that have an eye in the back of their heads. It has been observed in fruitflies that a protein called Pax6 can trigger the formation of extra eyes, suggesting that it plays a key role in the normal development of eyes. But scientists did not know whether the protein played the same role in higher mammals. Richard Lang of New York University Medical Center, USA, and his colleagues have shown that giving frog embryos an extra dose of Pax6 can cause a third eye to grow in the back of their heads by the time they are tadpoles. But it is believed that the protein cannot pull off this trick on its own and other factors must be involved because the eyes grow only in the head region ( Development , Vol 126, p4213).

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