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Observatory: The Gene That Tells Planaria Worms Which End Is UpThe flatworms known as planaria have long amazed scientists with their capacity for regeneration. Cut off the head end of one, and it regrows a head. Cut off the tail end, and it regrows a tail. As little as one three-hundredths of a worm can regenerate a complete organism. Chris GashRelated Observatory: When Removing One Predator Harms the Prey (December 11, 2007) Observatory: Scientists Blend Materials to Create Oil-Repellent Surfaces (December 11, 2007) More Observatory Columns »Web Link Smed-{beta}catenin-1 Is Required for Anteroposterior Blastema Polarity in Planarian Regeneration (Science) “They are some of the champions of regeneration,” said Peter W. Reddien of the Massachusetts Institute of Technology and the Whitehead Institute for Biomedical Research. But as much as they have amazed scientists, planaria have also confounded them. While researchers know that stem cells are involved in regeneration, no one has been able to determine how the “polarity” occurs, how a worm knows whether to make a head or a tail based on where the wound is. Dr. Reddien, with a colleague, Christian P. Petersen, is the author of one of two papers in Science that solve some of the mystery. A single gene is responsible for the polarity. Dr. Reddien used a process called RNA interference that allows researchers to “turn off” genes one by one and see what occurs. By turning off a gene called Smed-betacatenin-1, the researchers found that a worm with a tail wound would regenerate a head, not a tail. In fact, Dr. Reddien said, they found that they could make as many as six side incisions and that the worms would grow a head at each. Needless to say, Dr. Reddien acknowledged, “this is the most dramatic effect I’ve seen.” Dr. Reddien said that after a wound, other genes known as Wnt genes become activated at the site, producing signaling chemicals that activate the regeneration gene. In their work, the researchers essentially shut down this signaling pathway. In the second Science paper, Alejandro Sánchez Alvarado and colleagues at the University of Utah turned up the signaling activity, creating tails in place of heads. Dr. Reddien said more work needed to be done to learn what initiates the Wnt genes and how Smed-betacatenin-1 then regulates regeneration in stem cells. “We know what the switch is,” he said. “Now we want to know who throws the switch, and once it’s thrown, what happens.” Tag CloudExternal InformationAdditional InformationSenate Adopts Energy Bill Raising Mileage for Cars...Ethanol Is Feeding Hot Market for Farmland... Amazon’s ?Forest Peoples? Seek a Role in Striking Global Climate Agreements... Gas Emissions Rarely Figure in Investor Decisions... Where Am I?News Main Page - Business - Observatory: The Gene That Tells Planaria Worms Which End Is Up |
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