Over 6,000 genes influence body weight in mice

Monell Center researchers say that more than 6,000 genes, about 25 per cent of the genome, contribute to obesity and body weight in mice.

Washington, January 15 : Monell Center researchers say that more than 6,000 genes, about 25 per cent of the genome, contribute to obesity and body weight in mice.

This is for the first time that a research team has carried out a study to count the number of genes that influence body weight.

"Reports describing the discovery of a new 'obesity gene' have become common in the scientific literature and also the popular press," said study author Michael G. Tordoff, behavioural geneticist at the Monell Center.

"Our results suggest that each newly discovered gene is just one of the many thousands that influence body weight, so a quick fix to the obesity problem is unlikely," he added.

During the study, the researchers surveyed the Jackson Laboratory Mouse Genome Database for information on body weights of knockout mouse strains.

The term 'knockout mice' is used for rodents that have had a specific gene inactivated, or "knocked out".

Studying how the knockout mice differ from normal mice provided researchers with information about that gene's function, and how it might contribute to disease.

The reason why the researchers selected data about mice was simply because they share many genes with humans and, thus, could provide valuable information on human disease.

The Monell survey revealed that body weight was altered in over a third of the viable knockout stains. It revealed that 31 per cent weighed less than controls, suggesting that the missing genes contribute to heavier body weight. Another 3 per cent weighed more, contributing to lighter weight.

Extrapolating from the total number of genes in the mouse genome, the researchers reckoned that over 6,000 genes could potentially contribute to the body weight of a mouse.

"It is interesting that there are 10 times more genes that increase body weight than decrease it, which might help explain why it is easier to gain weight than lose it," Tordoff said.

The implications of the new findings may extend beyond studies of obesity and body weight, for body weight is also associated with various diseases - viz., hypertension, diabetes, and heart disease.

Gene knockouts reported to affect these diseases and others could potentially be due to a general effect to lower body weight.

Monell geneticist and lead author of the study, Danielle R. Reed, says that the findings also hold clinical relevance.

"Clinicians and other professionals concerned with the development of personalized medicine need to expand their ideas of genetics to recognize that many genes act together to determine disease susceptibility," Reed said.

The study has been published in the online journal BMC Genetics.

ANI