JEEPERS! CREEPY PEEPERS!

By J. MADELEINE NASH

Imagine a creature with eyes everywhere--on the top of its head, on its chest, on its knees. Surely it must have leaped out of a monster movie, you say, or the caverns of ancient myth. But, no, this strange beast crawled--actually it flew--out of the pages of the august journal Science last week. In a new study, researchers from the University of Basel in Switzerland described how they genetically engineered swarms of bizarre fruit flies-not as an attention-grabbing stunt but as part of a serious effort to understand how nature fashions something as magnificent as an eye.

Scientists have long considered the highly variable organ of vision--from the kaleidoscopic eyes of insects to the gleaming eyes of cats--to be one of the greatest puzzles among all the structures invented by evolution. Did biology draw up a blueprint for eyes many times? Or are all eyes assembled according to the same rules?

To find out, developmental biologist Walter Gehring and two colleagues focused on a gene known as eyeless. Fruit flies that lacked this gene, they knew, failed to develop eyes. But the researchers wanted to know more about the powers of eyeless. So they inserted multiple copies of the gene into minuscule fruit-fly embryos, and the results were no less than eerie. The flies grew normal eyes--sparkling red, like multifaceted rubies--but they were all over: on the legs, the wings, the antennae. There were up to 14 eyes per fly.

The news stunned developmental biologists around the world. For until now, no one suspected that the eyeless gene was so powerful, capable of taking precedence over other genes, like those responsible for elaborating wings and legs. That an eye might partly form on a limb made sense, but not so perfect an eye, complete with all its light receptors. Marvels William McGinnis, a Yale University biologist: "All you have to do, it seems, is switch on the eyeless gene, and you get these beautiful eyes."

Structurally, observes McGinnis, insect eyes are very different from the eyes of humans and other vertebrates. For instance, fruit-fly eyes are compound, meaning they are composed of many (in this case 800) individual units, each with its own miniature lens. The difference between a mouse eye, say, and a fruit-fly eye is so enormous that many scientists have argued that the genetic programs responsible for creating different kinds of eyes must have evolved independently.

Yet when Gehring and his team replaced eyeless with a gene that controls eye development in mice, they found that the mouse gene also produced flies with multiple eyes. The implication was inescapable: the mammalian gene and the fly gene are so closely related that they are almost certainly derived from a precursor gene in a common ancestor--quite possibly some sort of sea-dwelling worm that lived 500 million or so years ago. "What does this mean?" asks molecular biologist Charles Zuker, of the Howard Hughes Institute in San Diego, with a half smile. "It means that we are basically just big flies."

The buzz Gehring created is unlikely to simmer down anytime soon. For master control genes like eyeless, which span the vertebrate and invertebrate worlds, are keys to millions of years of evolution, and scientists are already racing to find more of these revealing snippets of DNA.

--With reporting by David Bjerklie/New York

With reporting by David Bjerklie/New York