By Ryan Flinn and Reg Gale - 2012-05-18T04:01:00Z

Rare DNA mutations are so plentiful in the human genome that they make it difficult to precisely identify the genetic switches that cause many common human diseases, two studies found.

The data, released yesterday in the journal Science, shows that the vast majority of genetic variations found in people are rare and evolutionarily recent. Well-known DNA variations that are common across large populations probably dont widely affect many illnesses, the authors said.

The research means it may be more difficult to isolate the roots of ailments such as diabetes and heart disease, and cures will be more elusive, said Joshua Akey, associate professor of genome sciences at the University of Washington in Seattle and an author of the study.

The task of correlating individual variants with particular diseases is probably more complicated than we would have anticipated a few years ago, Akey said in an interview. Its exciting because were starting to see patterns of variation we were never able to access before because the technology wasnt there, and its frustrating because we dont know what it means.

In a study of 2,440 people from Europe and Africa, the researchers discovered about a half-million mutations, most of which were rare, novel or population-specific. The second effort, led by Matthew Nelson and Vincent Mooser of London-based drugmaker GlaxoSmithKline Plc (GSK), targeted DNA that was already considered to have potential for medical development.

The findings highlight issues involved in the trend toward personalized medicine, in which drugmakers seek to determine whether a patient is genetically susceptible to a particular disease or would be especially responsive to certain treatments. More than 72 such therapies are available now, a fivefold increase from the 13 available in 2006, according to the Personalized Medicine Coalition, an industry advocacy group based in Washington.

It could have significant implications for our health and medicine, Eric Topol, director of the Scripps Translational Science Institute in La Jolla, California, said in an interview. That whole common-disease, common-variant theory continues to have holes punched in it.

Last month a different study concluded sequencing the genomes of patients to reveal what ailments might mar their futures wasnt the best predictor for the most common diseases.

That study didnt sequence individuals. Instead, researchers collected data from thousands of identical twins in five countries and used a computer model to determine the effectiveness of genome sequencing. They concluded most people would get negative results from having their genome sequenced for all except one of 24 identified conditions, including heart disease, diabetes and Alzheimers.

Originally posted here:
Rare DNA Mutations Raise Question Theories of Disease