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5 December 2013 11:26 am ,
Vol. 342 ,
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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14 April 2004 (All day)
Seafaring stickleback fish sport a pair of prominent spines sticking out from their pectoral fins. Their freshwater cousins look far less threatening, outfitted with much smaller spines. Now researchers have found that a simple change of gene activity could make all the difference--a rare demonstration of how a small genetic change can make a relatively rapid impact on an organism.
Sticklebacks started out as saltwater fish. As the glaciers of the last Ice Age receded 10,000 years ago, some of these fish swam inland, and many became trapped in lakes left behind by the glacial melt. Over time, the lake fish came to look quite different from their marine forefathers. These populations are now natural laboratories for evolutionary studies.
One prominent difference is the pelvic spines. Marine fish have prominent spines, presumably to deter predators, but the freshwater fish have only small ones, if any at all. That's probably because their new environment was short of the minerals needed to make the spines, which made spine-building consume too much of the fishes' energy to be worthwhile. By breeding saltwater and freshwater fish, David Kingsley, a vertebrate geneticist at Stanford University, and his colleagues have tracked down the genetic basis for the loss of the spines, showing that the spines didn't simply disappear for lack of raw materials. The breeding studies first helped his team home in on parts of the genome responsible for spine formation. They then began looking at genes in the region that seemed particularly influential and focused on a gene called Pitx1.
By using genetic markers to follow Pitx1 expression during development, they found that it was active in the incipient pelvic girdle of marine sticklebacks but not in the freshwater fish. Elsewhere in the bodies of the marine fish, Pitx1 was just as active as in freshwater fish, suggesting that a change in the gene's regulation--and not in the gene itself--caused the lake sticklebacks to lose their spines, the team reports in the 15 April issue of Nature. As further support they noted that mice with no Pitx1 activity have smaller than normal hind limbs and are asymmetrical, just like the freshwater stickleback.
The study is important, because it shows that “relatively simple genetic changes can have profound effects,” says R. Craig Albertson, an evolutionary biologist at the Forsyth Institute in Boston, Massachusetts.