Another Obesity-Associated Gene

NATIONAL CANCER INSTITUTE, BILL BRANSON For years, scientists have suspected that the FTO gene was somehow linked to obesity. Now, researchers led by Marcelo Nobrega of the University of Chicago have shown that the obesity-associated portions of FTO are linked to a distant gene called IRX3, according to a study published yesterday (March 12) in Nature. The researchers found that portions of the FTO gene were involved in switching on a promoter of IRX3, which encodes a transcription factor and is highly conserved in mice, zebrafish, and humans.

In 2007, researchers found that variants of the FTO gene were linked to obesity, but despite intense scrutiny, no direct link was found. “Now, we offer an explanation for that. They were looking at the wrong gene,” Nobrega told the Agence France-Press.

The research team found that in brain tissue samples from people with an obesity-linked mutation in FTO, IRX3 was highly expressed, although FTO was not. Mice lacking the IRX3 gene not only weighed 25 percent to 30 less than those that had it, these animals didn’t gain any weight on a high-fat diet and were seemingly resistant to diabetes.

“It’s a timely reminder that when contemplating the scene of a crime, it is wise to look beyond those potential culprits standing nearest to the body, some of whom may well be innocent bystanders, and to look for ‘motive’ amongst those who may be standing a little distance away,” Mark McCarthy of the University of Oxford, a researcher who has worked on the connection between obesity and the FTO gene, told National Geographic’s Not Exactly Rocket Science.