Scientific American February 1999 [antikvár]

from the Editors Worm Gets the Early Bird / ea, the stars are not pure in his sight," reads the Book of Job. I "How much less man, that is a worm?" Typical. As Bartlett's Fa-' miliar Quotations will attest, worms are the most famously low vermin in literature. People are usually the writers' real targets, but worms take the rhetorical beating. Jonathan Edwards, for instance, invoked them to rail, "A little, wretched, despicable creature; a worm, a mere nothing, and less than nothing; a vile insect that has risen up in contempt against the majesty of Heaven and earth." Worms are the acme of insignificance. And yet biologists love them. Granted, researchers' affection falls mainly on the roundworm Caenorbahditis elegáns, an inoffensive microscopic beastie. As I write this, John E. Sulston of the Sanger Center in England and Robert H. Waterston of Washington University have only just published the complete genetic sequence for C. elegáns. For the first time, science knows all the genetic information that makes up a multicellular animal. That brilliant accomplishment foretells the completion of the Human Genome Project just a few years from now, when we will similarly know all the genes of humans. Bruce Alberts, the president of the National Academy of Sciences, quotably remarked to the Neiu York Times, "In the last 10 years we have come to realize humans are more like worms than we ever imagined." (He meant this genomic work, not the rise of the ]erry Springer Shotu.) We and the worms share many of the same genes—and why not? By and large, we're made of the same proteinaceous stuff. The differences mostly reflect proportion and organization. The great mystery is how that DNA directs development, telling one cell how to grow into a well-formed creature of differentiated tissues. C elegáns furthers that pursuit, too, but only so far. Past that, we need to turn to other creatures and other methods. Roundworms are ill equipped, for example, to teach us how limbs develop—and not merely because they don't have feet. Rather C. elegáns lacks even some of the ancient genes that evolution later co-opted for building vertebrate fins, legs, wings and arms. Chick embryos are better choices: they are easily manipulated and anatomical cousins to humans. Robert D. Riddle and Clifford J. Tabin bring us up to date in "How Limbs Develop," beginning on page 54. CHICK EMBRYO holds clues to development that worms cannot. JOHN RENNIE, Editor in Chief [email protected]