Gene mapping for everyone? Study says not so fast

WASHINGTON (AP) — Gene scans for everyone? Not so fast. New research suggests that for the average person, decoding your own DNA may not turn out to be a really useful crystal ball for future health.

Today, scientists map entire genomes mostly for research, as they study which genetic mutations play a role in different diseases. Or they use it to try to diagnose mystery illnesses that plague families. It’s different from getting a genetic test to see if you carry, say, a particular cancer-causing gene.

But as genome mapping gets faster and cheaper, scientists and consumers have wondered about possible broader use: Would finding all the glitches hidden in your DNA predict which diseases you’ll face decades later?

Johns Hopkins University developed a model using registries of thousands of identical twins, who despite their shared genes can develop different diseases. They examined 24 ailments, including different types of cancer, heart disease, diabetes and Alzheimer’s.

Under best-case scenarios, most people would be told they had a somewhat increased risk of at least one disease, said Dr. Bert Vogelstein, a Hopkins cancer geneticist and the study’s senior author.

But a negative test for most of the rest of the diseases doesn’t mean you won’t get them. It just means that you’re at no more risk than the general population. Those are the findings Vogelstein’s team reported Monday in the journal Science Translational Medicine. Why? Cancer, for example, typically doesn’t result from inherited genes but from mutations that can form anytime, Vogelstein explained. Many other common diseases are influenced by lifestyle and environment — so you’d still have to eat well, exercise and take the other usual precautions.

The study examined just one possible future use of genome mapping. It doesn’t mean there aren’t other benefits from the effort.

Make no mistake: This technology does have huge promise for customizing care for certain people, especially children with otherwise undiagnosed illnesses, said Dr. James Lupski of Baylor College of Medicine, who wasn’t involved in Monday’s study.

Last year, Baylor researchers reported one of the first examples of genome mapping directly benefiting a patient. It found a mutation that pointed to the right treatment for a 14-year-old girl’s baffling trouble breathing.

But even if finding a genetic explanation doesn’t lead to treatment, knowing whether it was inherited can help parents decide whether to chance having another baby, Lupski added.

“There are families where this can be transformative,” said Lupski. He had his own genome mapped to identify the cause of a rare nerve disorder.

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Personal Gene Mapping Has Limits, Study Says

MONDAY, April 2 (HealthDay News) — Many people have pinned their hopes on human genome scans as the cornerstone of the rapidly emerging field of personalized medicine, able to predict the future health of individuals.

But there may be limits to what information whole genome sequencing can provide, according to new research slated for presentation Monday at the American Association for Cancer Research annual meeting in Chicago. The study will be simultaneously published online in Science Translational Medicine.

“In most cases, genome sequencing is not going to tell people what disease they’re going to get or die from. It can be valuable in telling what diseases they have an excess risk for,” said study co-author Dr. Bert Vogelstein, director of the Ludwig Center for Cancer Genetics and Therapeutics at Johns Hopkins University in Baltimore.

“Genome sequencing is not going to be the dominant component of patient care,” he added. “It will not be a substitute for preventive medicine strategies incorporating routine check-ups, exercise, physical status, lifestyle.”

The costs of whole genome sequencing are plummeting, making the test more accessible to more people, yet the ability of the test to provide useful information to patients has not been studied quantitatively, Vogelstein said.

The authors used data on identical twins in registries in Sweden, Denmark, Finland and Norway, as well as a U.S. registry of World War II military veteran twins, to look at genetic risk for 24 common diseases including diabetes, Alzheimer’s and breast cancer.

The researchers calculated that genetic sequencing would reveal a predisposition to at least one disease in 90 percent of the twins studied.

But that’s only predisposition, not whether you actually fall ill or not. The actual risk of getting one of these conditions would be no different from that of the general population, the authors noted.

The analysis also concluded that most individuals would receive negative test results for 23 of the 24 diseases but, again, this hypothetical information would not necessarily predict the future. Even with a negative test result, the risk for developing most of the diseases for which one tested negative would still be 50 percent to 80 percent of that in the general population.

To put the results in context: 2 percent of women who undergo whole genome tests will likely get a positive result for ovarian cancer risk, explained Vogelstein, who is also an investigator at the Howard Hughes Medical Institute, in Chevy Chase, Md.

That puts their overall risk of developing a tumor in their lifetime at 10 percent.

And the 98 percent of women who get a negative result don’t necessarily get a “get-out-of-jail-free pass” as they still harbor the same risk as the general population, Vogelstein said.

If it comes down to a choice between spending money on a genome test and spending it on health measures such as regular check-ups and joining a gym, it might be wise to go with the latter, he said.

“If I spend it on a gym membership, that will definitely decrease my risk for ovarian cancer,” Vogelstein said.

On the other hand, a genetic test might seem prudent for someone with a family history of a specific disease.

Commenting on the study, Dr. Marc Williams, vice president of clinical genetics for the American College of Medical Genetics and Genomics in Salt Lake City, said: “There’s certainly some promise in this type of testing but we’re still trying to sort out what are the best situations in which to apply this type of whole genome technology.”

Williams pointed out that “if we broadly apply it without thinking about the clinical context — why we are doing the test, what we hope to learn — then we could get into a lot of trouble in terms of coming up with a lot of information we don’t know what to do with.”

In the end, though, said study author Vogelstein, it comes down to an individual decision.

More information

The Human Genome Project has more on genetic sequencing.

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Gene mapping for everyone? Study says not so fast

WASHINGTON (AP) — Gene scans for everyone? Not so fast. New research suggests that for the average person, decoding your own DNA may not turn out to be a really useful crystal ball for future health.

Today, scientists map entire genomes mostly for research, as they study which genetic mutations play a role in different diseases. Or they use it to try to diagnose mystery illnesses that plague families. It’s different from getting a genetic test to see if you carry, say, a particular cancer-causing gene.

But as genome mapping gets faster and cheaper, scientists and consumers have wondered about possible broader use: Would finding all the glitches hidden in your DNA predict which diseases you’ll face decades later?

Johns Hopkins University developed a model using registries of thousands of identical twins, who despite their shared genes can develop different diseases. They examined 24 ailments, including different types of cancer, heart disease, diabetes and Alzheimer’s.

Under best-case scenarios, most people would be told they had a somewhat increased risk of at least one disease, said Dr. Bert Vogelstein, a Hopkins cancer geneticist and the study’s senior author.

But a negative test for most of the rest of the diseases doesn’t mean you won’t get them. It just means that you’re at no more risk than the general population. Those are the findings Vogelstein’s team reported Monday in the journal Science Translational Medicine. Why? Cancer, for example, typically doesn’t result from inherited genes but from mutations that can form anytime, Vogelstein explained. Many other common diseases are influenced by lifestyle and environment — so you’d still have to eat well, exercise and take the other usual precautions.

The study examined just one possible future use of genome mapping. It doesn’t mean there aren’t other benefits from the effort.

Make no mistake: This technology does have huge promise for customizing care for certain people, especially children with otherwise undiagnosed illnesses, said Dr. James Lupski of Baylor College of Medicine, who wasn’t involved in Monday’s study.

Last year, Baylor researchers reported one of the first examples of genome mapping directly benefiting a patient. It found a mutation that pointed to the right treatment for a 14-year-old girl’s baffling trouble breathing.

But even if finding a genetic explanation doesn’t lead to treatment, knowing whether it was inherited can help parents decide whether to chance having another baby, Lupski added.

“There are families where this can be transformative,” said Lupski. He had his own genome mapped to identify the cause of a rare nerve disorder.

View the original article here

Mapping the brain’s superhighways

Curved sheets of fibers in the left hemisphere of a human brain are woven together like fabric, a new study reveals. Courtesy of MGH-UCLA Human Connectome Project

The impossibly complicated brain just got a little simpler. Instead of looking like a tangled mess of noodle soup, pathways in the brain are arranged more like a package of neatly interwoven ramen noodles, a new brain scanning study reveals. The results offer more clues to how the human brain gets built and how it has evolved.

Scientists led by Van Wedeen of Massachusetts General Hospital and Harvard Medical School in Boston used a scanning technique called diffusion magnetic resonance imaging that detects the direction of traffic flow along white matter tracts, the brain’s information superhighways. The scans revealed that these brain signals form a grid, made up of parallel and perpendicular tracts woven together into curved sheets. 

This grid is a general feature of primate brains, Wedeen and colleagues report in the March 30 Science. Brains of rhesus monkeys, owl monkeys, marmosets and prosimian galagos contained similar geometric patterns to those found in human volunteers, suggesting the grid’s deep evolutionary roots.

One day, doctors may be able to diagnose brain disorders by identifying variations in this regular brain pattern. 

Found in: Body & Brain

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