Magazine article Science News

When Mice Fly: Bat DNA Leads to Longer Limbs in Mouse Embryos

Magazine article Science News

When Mice Fly: Bat DNA Leads to Longer Limbs in Mouse Embryos

Article excerpt

Give a mouse embryo a stretch of bat DNA, and its limbs grow a little longer, a new genetic study shows. The change, though small, may illustrate one evolutionary step on the path to wings.

Charles Darwin suggested that a series of such minor changes would be key to building new body features, like wings, from old ones. "If you have lots of these changes over time--and with natural selection--ultimately you'll end up with some structure like a bat wing," says study leader Richard Behringer, a developmental biologist at the University of Texas M.D. Anderson Cancer Center in Houston.

To support this idea, Behringer's team examined a gene called Prxl that controls bone growth by turning on other genes. Lab mouse embryos missing the gene grow puny limbs and misshapen heads, and pups die at birth. A short stretch of DNA near, but not part of, Prxl enhances its activation, helping a cell control how much of the gene's protein gets made.

The short-tailed fruit bat, with wings analogous to the front legs of mice, has a virtually identical version of Prxl. However, the enhancing stretch of DNA varies greatly between bats and mice, which are separated by 80 million to 100 million years of evolution. To test the effects of this difference, Behringer's team spliced the bat version of the enhancer into normal lab mice. In the limb bones of the mutant mice, Prxl was 70 percent more active than in unaltered mice.

More striking, the mutant embryo limbs grew slightly longer than those of normal mice, when measured a couple of days before birth. …

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