DNA Swap Between Eggs May Curb Inherited Disorders, Study Finds

April 14, 2010, 4:59 PM EDT  BusinessWeek

By Kristen Hallam

April 14 (Bloomberg) — Scientists discovered a way to transfer DNA from one fertilized human egg to another in a pioneering effort to avert the spread of a host of genetic disorders such as learning disabilities and diabetes.

The researchers at Newcastle University in northern England extracted the genetic material contributed by the egg and sperm and implanted it into a donor egg, according to the study published today by the journal Nature. It’s the first time DNA has been transferred between two fertilized human eggs.

The approach discards almost all the defective DNA inherited from the mother that disrupts the tiny energy generators inside cells, and may prevent related disorders such as blindness and liver failure, the researchers said. They are planning further experiments to see whether the technique could help people who carry mutated genes to have healthy babies — an end result that may still be a decade away.

“We have no way of curing these diseases at the moment, but this technique could allow us to prevent the diseases occurring in the first place,” said Doug Turnbull, the lead researcher and a professor at the university’s medical school, in a statement. “It is important that we do all we can to help these families and give them the chance to have healthy children, something most of us take for granted.”

Parents contribute a total of 23,000 genes to a child. In a fertilized egg, this genetic material is housed in two pronuclei, one from the egg and one from the sperm. The egg also contains mitochondria, tiny structures found in every cell that produce the chemical fuel needed for life. Mutations in the mitochondrial DNA, which are passed on from the mother, can disrupt the functioning of these energy generators.

‘Changing the Batteries’

The Newcastle scientists were able to extract both pronuclei and implant the material that makes each child unique into a donor egg with healthy mitochondria. They created 80 fertilized eggs using the technique and grew them in a laboratory for six to eight days. That showed for the first time that eggs produced in this way could reach the stage at which they each had divided into about 100 cells.

“It’s like changing the batteries,” Turnbull said today at a news conference in London. “These are diseases where there is battery failure. Because mitochondria are everywhere, these diseases can affect all parts of the body. None of my patients is exactly the same.”

About 1 out of every 200 children is born each year with mutations in mitochondrial DNA that cause no symptoms or only mild conditions. One in every 6,500 children is born with a more serious mitochondrial disease, ranging from muscular weakness to fatal heart failure. Some disorders lead to death in early infancy.

The research was funded by the Muscular Dystrophy Campaign, the U.K. Medical Research Council and the London-based Wellcome Trust, the world’s second-biggest medical research charity.

–Editors: Phil Serafino, Angela Cullen

To contact the reporter on this story: Kristen Hallam in London at khallam@bloomberg.net

To contact the editor responsible for this story: Phil Serafino at pserafino@bloomberg.net

DNAWellnessinfo.com Resource:  http://www.businessweek.com/news/2010-04-14/dna-swap-between-eggs-may-curb-inherited-disorders-study-finds.html

Key protein aids in DNA repair

April 11, 2010- physorg.com

Scientists have shown in multiple contexts that DNA damage over our lifetimes is a key mechanism behind the development of cancer and other age-related diseases. Not everyone gets these diseases, because the body has multiple mechanisms for repairing the damage caused to DNA by aging, the environment and other human behaviors – but the mechanisms behind certain kinds of DNA repair have not been well-understood.

In a paper published today in the journal Nature, researchers at the University of North Carolina at Chapel Hill’s Lineberger Comprehensive Cancer Center have shown that a particular protein – called Ku – is particularly adept at healing damaged strands of DNA.

According to Dale Ramsden, PhD, associate professor in the department of biochemistry and biophysics and a member of the curriculum in genetics and molecular biology, Ku is a very exciting protein because it employs a unique mechanism to repair a particularly drastic form of DNA damage.

“Damage to DNA in the form of a broken chromosome, or double strand break, can be very difficult to repair – it is not a clean break and areas along the strand may be damaged at the level of the fundamental building blocks of DNA – called nucleotides,” he notes.

Broken chromosomes can be compared to a break in a strand of yarn made up of several different threads or plies. Unless scissors are used to cut the yarn, the strand frays and may break or be damaged at several different places up and down the length of the yarn. These rough ends get “dirty” – making them harder to repair.

Provided by University of North Carolina

DNAWellnessinfo.com Resource:  http://www.physorg.com/news190207556.html

Disease Cause Is Pinpointed With Genome

Article by Nicholas Wade – New York Times
Published: March 10, 2010

Two research teams have independently decoded the entire genome of patients to find the exact genetic cause of their diseases. The approach may offer a new start in the so far disappointing effort to identify the genetic roots of major killers like heart disease, diabetes and Alzheimer’s.

In the decade since the first full genetic code of a human was sequenced for some $500 million, less than a dozen genomes had been decoded, all of healthy people.

Geneticists said the new research showed it was now possible to sequence the entire genome of a patient at reasonable cost and with sufficient accuracy to be of practical use to medical researchers. One subject’s genome cost just $50,000 to decode.

“We are finally about to turn the corner, and I suspect that in the next few years human genetics will finally begin to systematically deliver clinically meaningful findings,” said David B. Goldstein, a Duke University geneticist who has criticized the current approach to identifying genetic causes of common diseases.

Besides identifying disease genes, one team, in Seattle, was able to make the first direct estimate of the number of mutations, or changes in DNA, that are passed on from parent to child. They calculate that of the three billion units in the human genome, 60 per generation are changed by random mutation — considerably less than previously thought.

The three diseases analyzed in the two reports, published online Wednesday, are caused by single, rare mutations in a gene.

In one case, Richard A. Gibbs of the Baylor College of Medicine sequenced the whole genome of his colleague Dr. James R. Lupski, a prominent medical geneticist who has a nerve disease, Charcot-Marie-Tooth neuropathy.

In the second, Leroy Hood and David J. Galas of the Institute for Systems Biology in Seattle have decoded the genomes of two children with two rare genetic diseases, and their parents.

More common diseases, like cancer, are thought to be caused by mutations in several genes, and finding the causes was the principal goal of the $3 billion human genome project. To that end, medical geneticists have invested heavily over the last eight years in an alluring shortcut.

But the shortcut was based on a premise that is turning out to be incorrect. Scientists thought the mutations that caused common diseases would themselves be common. So they first identified the common mutations in the human population in a $100 million project called the HapMap. Then they compared patients’ genomes with those of healthy genomes. The comparisons relied on ingenious devices called SNP chips, which scan just a tiny portion of the genome. (SNP, pronounced “snip,” stands for single nucleotide polymorphism.) These projects, called genome-wide association studies, each cost around $10 million or more.

The results of this costly international exercise have been disappointing. About 2,000 sites on the human genome have been statistically linked with various diseases, but in many cases the sites are not inside working genes, suggesting there may be some conceptual flaw in the statistics. And in most diseases the culprit DNA was linked to only a small portion of all the cases of the disease. It seemed that natural selection has weeded out any disease-causing mutation before it becomes common.

The finding implies that common diseases, surprisingly, are caused by rare, not common, mutations. In the last few months, researchers have begun to conclude that a new approach is needed, one based on decoding the entire genome of patients.

The new reports, though involving only single-gene diseases, suggest that the whole-genome approach can be developed into a way of exploring the roots of the common multigene diseases.

“We need a way of assessing rare variants better than the genomewide association studies can do, and whole-genome sequencing is the only way to do that,” Dr. Lupski said.

With 10 genomes of healthy humans sequenced, Dr. Gibbs, a specialist in DNA sequencing, decided it was time to decode the genome of someone with a genetic disease and asked his colleague Dr. Lupski to volunteer.

Mutations in any of 39 genes can cause Charcot-Marie-Tooth, a disease that impairs nerves to the hands and feet and causes muscle weakness.

Fifty thousand dollars later, Dr. Lupski turned out to have mutations in an obscure gene called SH3TC2. The copy of the gene he inherited from his father is mutated in one place, and the copy from his mother in a second.

Both his parents had one good copy of the gene in addition to the mutated one. A single good copy can generate enough, or nearly enough, of the gene’s product for the nerves to work properly. Dr. Lupski’s mother was free of the disease and his father had only mild symptoms.

In the genetic lottery that is human procreation, two of their eight children inherited good copies of SH3TC2 from each parent; two inherited the mother’s mutation but the father’s good copy and are free of the disease; and four siblings including Dr. Lupski inherited mutated copies from both parents. These four all have Charcot-Marie-Tooth disease. The results are reported in The New England Journal of Medicine.

In Seattle, Dr. Hood and Dr. Galas have also applied whole-genome sequencing to disease. They analyzed the genome of a family of four, in which the two children each have two single-gene diseases, called Miller syndrome and ciliary dyskinesia. With four related genomes available, the researchers could identify the causative genes. They also improved the accuracy of the sequencing because DNA changes that did not obey Mendel’s rules of inheritance could be classed as errors in the decoding process.

The Seattle team believes whole-genome sequencing can be applied to the study of the common multigene diseases and plans to sequence more than 100 genomes next year, starting with multigenerational families.

The family whose genomes they report in Science were sequenced by a company with a new DNA sequencing method, Complete Genomics of Mountain View, Calif., at a cost of $25,000 each. Clifford Reid, the chief executive, said that the company was scaling up to sequence 500 genomes a month and that for large projects the price per genome would soon drop below $10,000. “We are on our way to the $5,000 genome,” he said.

Dr. Reid said the HapMap and genomewide association studies were not a mistake but “the best we could do at the time.” But they have not yet revolutionized medicine, “which we are on the verge of doing,” he said.

Dr. Goldstein, of Duke University, said the whole-genome sequencing approach that was now possible should allow rapid progress. “I think we are finally headed where we have long wanted to go,” he said.

DNAWellnessinfo.com Resource:  http://www.nytimes.com/2010/03/11/health/research/11gene.html

Vital cues for cancer prevention through DNA repairing gene

Naveen Kumar, TNN, Mar 6, 2010, 10.23pm IST

VARANASI: Now, the study of DNA repairing gene using single nucleotide polymorphism (SNP) marker would provide vital cue for cancer prevention, especially neck and head that comprises of as many as seven different types of cancer in the facial region. In addition, the study would also enable early prediction of much feared breast cancer in women.

While a team of scientists is studying the genomics in cancer, especially the squamous cell carcinoma in neck, head and breast region under the Hap Map project, the case studies in the last five years have revealed interesting contribution of DNA repairing genes including P53 associated genes, where SNP can be used as a marker for prompt diagnostic purpose.

Senior scientist Central Drug Research Institute Lucknow Dr SK Rath told TOI on Saturday, “The studies have shown that P53 associated genes play a vital role in DNA repair and act as tumour suppressor. It changes the DNA repair scene and plays pivotal role in protection against mutagenic and cytotoxic effects of DNA damage that also prevents cancer.” Similarly, SNP could also provide vital cue for DNA repairing in BRAC 1 and 2 genes that are believed to cause breast cancer in women, he added.

It is to be mentioned here that Dr Rath is a key member of the team that studied genotype of cancerous and non-cancerous cells under the project in the Xth five-year plan. Now, the team is researching on SNP of different people including smokers and non-smokers, drinkers and non-drinkers, where the cause of cancer

could not be ascertained.

Saying that million of SNPs exist in human genome that occur in gene within the regulatory region, Dr Rath emphasised that the method detects the most common type of variation in the genome, as it cater to small alteration, providing better scope for prediction. The SNP markers are preferred for population genomic disease association and are good indicators of squamous cell carcinoma in neck and head region that includes cancers of oral cavity, pharynx, nasopharynx, oropharynx, hypopharynx and tongue, he added.

Stressing that cancers of neck and head region are growing at alarming rate in states like UP, he said the case studies in Lucknow revealed that out of 100 cancer patients, the number of patients with cancer in the neck and head region increased from 30 to 49 (150 per cent increase) in the last five years. Worldwide, it is the fifth most common type of cancer affecting over one million population annually, he concluded.

DNAWellnessinfo.com Resource:  http://timesofindia.indiatimes.com/city/varanasi/-Vital-cues-for-cancer-prevention-through-DNA-repairing-gene/articleshow/5648729.cms

A First: Diagnosis By DNA

Matthew Herper, 02.25.10, 11:20 AM EST
Forbes Magazine dated March 15, 2010

Last year a five-month-old boy in Turkey stopped gaining weight and became dehydrated despite getting plenty of liquids. Specialists in Istanbul suspected Bartter’s syndrome, a potentially fatal kidney disorder that afflicts one in 100,000 babies, causing dangerously low levels of potassium and salt.

To confirm their hunch they sent a blood sample to Yale Medical School geneticist Richard Lifton. They asked him to determine whether the baby had the gene defect implicated in Bartter’s. But Lifton thought that Bartter’s might not be the culprit. So he did something that would have been prohibitively expensive a few years ago. He deciphered the DNA letters for all the baby’s genes. The gene scan revealed that the baby’s problem was not Bartter’s but something else called congenital chloride diarrhea, which also lowers salt levels. The result means that the baby, now doing better on a special diet, could be treated with drugs if his condition gets worse.

The case, published in the Proceedings of the National Academies of the Sciences in October, may be the first in which the results of DNA sequencing have altered treatment of a patient. Does this herald the beginning of a new kind of medicine in which patients with unexplained symptoms get their DNA sequenced? Yes, says Lifton: “This will be a court of last resort to try and identify causes of disease.”

Gene researchers have talked for years about how sequencing will transform medicine. Now that sequencing is cheap this transformation is under way. The cost of deciphering all 6 billion letters in the human genome has dropped from $1 million in 2007 to less than $20,000 today. Lifton used a two-step method to extract and sequence only the 1% of those letters that contain known genes, lowering the price to $2,500. New DNA sequencers just introduced by Illumina ( ILMN – news – people ) (whose model Lifton used) and Life Technologies ( LIFE – news – people ) could lower the cost of sequencing a whole genome to below $3,000 by year-end.

DNA sequencers haven’t been approved for use in medical testing, and insurers don’t pay for sequencing. But peering into DNA is becoming an option for wealthy patients with rare and scary diseases. Knome, a privately held company in Cambridge, Mass., started out in 2008 charging $350,000 to arrange sequencing and interpret the data for wealthy patrons as a vanity project. Now it offers the scans for as little as $25,000. Chief Executive Jorge Conde says several patients hoping to improve their care are among his customers.

The $600 million annual market for DNA sequencers is still all about research, with Illumina holding a 60% market share. But numerous companies are already jockeying for position in anticipation of a big future medical-test market.

Cancer patients may be among the first to benefit from DNA sequencing technology. In one early example of how this may work, Marco Marra, a researcher at the Michael Smith Genome Sciences Centre in Vancouver, last year sequenced the genes from a tumor that had spread from an 80-year-old patient’s tongue to his lungs. There is no standard therapy for this type of tumor. But the gene scan found the tumor was making large amounts of a growth-promoting protein called RET. When the patient’s medicine was switched to Pfizer ( PFE – news – people )’s Sutent, a drug that blocks this protein, the tumor shrank, according to a report in Nature.

A looming question is how the Food & Drug Administration will regulate sequencing technology. It could treat DNA sequencing like genetic tests and require separate approvals for each use. Some equipment makers hope for a faster path in which doctors practicing a new medical specialty emerge to evaluate and interpret gene scans, as radiologists do with X-rays. Clifford Reid, chief executive of Complete Genomics, which has finished 50 genomes, is skeptical that it will be that easy. “The FDA has been very quiet up until now,” he says. “We all have to expect the FDA to be intimately involved with these new tests.”

DNAWellnessinfo.com Resource:  http://www.forbes.com/forbes/2010/0315/health-illumina-genome-cancer-diagnosis-by-dna.html

Blood Tests May Reveal Tumor Size

Feb. 22, 2010 – cbsnews.com

(CBS) This article was written by Discover’sAndrew Moseman.

Doctors who are torn over how aggressively to treat a cancer patient, not knowing whether a tumor has fully regressed or is coming back, might someday be able to find out just by testing the patient’s blood. In a study forthcoming his week in Science Translational Medicine, John Hopkins researchers say they have tested a way to spot the “fingerprint” of cancer-the changes to the

Jeffery Schloss of the National Human Genome Research Institute, who wasn’t involved in the study, likened the approach to drawing a map. Sequencing the letters of the genetic code would be akin to plotting every house in a large neighborhood. The Hopkins team was looking only for neighborhoods-in particular, neighborhoods out of place compared with where they would be in normal tissue. The researchers in the study looked at tissue from people with breast or bowel cancer, and found multiple DNA rearrangements in each of the samples of cancerous tissue.

In each patient, the genetic changes in the cancerous cells amount to a unique marker of the patient’s tumor, the researchers say. Using blood samples from two of the colorectal cancer patients, they found the test was sensitive enough to detect this marker or “fingerprint” DNA that had been shed by tumors into the bloodstream.

The study’s approach could be invaluable for tracking the progress of a tumor. When a cancer is operated on or treated with radio – or chemotherapy, the levels of the fingerprint should fall, and vanish altogether if the tumor has been eradicated. Indeed, in one of their patients, the study authors saw the cancer biomarker drop after surgery but then rise again, suggesting to them that the cancer wasn’t fully eradicated.

Because the technique requires sequencing a person’s whole genome, it’s not coming to a hospital near you in the immediate future, says study author Bert Vogelstein: “This is really personalized medicine. This is not something off the shelf…. This is something that has to be designed for each individual patient”. But with the cost of genome sequencing rapidly coming down in price, this kind of approach might not be too far away, and doctors could use it to catch a recurring cancer before it’s large enough to be visible to other methods, like CT scans.


By Andrew Moseman
Reprinted with permission from Discover

DNAWellnessinfo.com Resource: http://www.cbsnews.com/stories/2010/02/22/tech/main6232081.shtml

Secrets of attraction may lie in immune system DNA

BY Rosemary Black
DAILY NEWS STAFF WRITER

Wednesday, February 17th 2010, 5:04 PM

Here’s some new information about the science of attraction: Your body odor may provide your mate with subconscious clues about the strength of your immune system.

Researchers from the University of Western Australia, reporting in the journal “Animal Behavior,” say that whether or not the object of your desire finds you irresistible may depend on how sweet your sweat smells, according to a report in the Daily Mail. A woman’s sweat holds genetic information that signals to a potential hubby whether their offspring would possess the best chance of fighting off illness.

The more varied a woman’s histocompatibility, or MHC, genes are, the more attractive she appears to the opposite sex.

The researchers studied the DNA of nearly 150 college students, who filled out questionnaires about their love lives. They looked at the students’ DNA to find variation in genes that are known to have an influence on the immune system, and found that the more diverse these genes were, the more disease-resistant a person was.

The researchers then matched the results of the genetic tests with the survey answers and learned that the women with the most varied histocompatibility (MHC) genes also had the greatest number of sexual partners.

Previous research has shown that the more different a person’s perspiration is to yours, the more pleasant you’re likely to find him or her. It’s theorized that this phenomenon came about so people wouldn’t accidentally marry their relatives or anyone else who’s genetically similar.

Another theory is that women with varied MHC genes could be more outgoing.

“It is possible that MHC-diverse women have more sexual partners because they actively seek more partners, rather than because males prefer diverse partners,” wrote the researchers.

Relationship expert Laurent Mackler says parents may affect how successful a woman is at finding a boyfriend – but not necessarily because of genetics.

“We are invariably attracted to people based on how familiar that person is to us from childhood,” says Mackler, author of “SoleMate: Master the Art of Aloneness & Transform Your Life.”

“As human beings, we are always seeking homeostasis, or balance, and looking for the parts of us that got lost as we grew up and had to adapt to the family system. So we’re attracted unconsciously to the people who embody these traits. We are looking for our other half and may not always find him.”

DNAWellnessinfo.com Resource:  http://www.nydailynews.com/lifestyle/health/2010/02/17/2010-02-17_secrets_of_attraction_may_lie_in_immune_system_dna_thats_sensed_through_sweat_sc.html

A new theory of how low doses of antibioitics create antibiotic resistance

Feb 11, 2010 – usatoday.com

E.coli bacteria is seen under a microscope.

CAPTION

By Centers for Disease Control

Exposure to low levels of antibiotics increases mutations in E. coli and Staphylococcus bacteria hundreds of time more than normal, making the creation of drug-resistance strains more likely, says a paper in today’s edition of the journal Molecular Cell.

This finding adds to concerns about antibiotic resistance brought on by poor prescriptions practices among doctors, patients who don’t take all their medicine and even low doses of antibiotics given to help animals grow faster.

The researchers found that while low levels of antibiotics may not be enough to kill off the bacteria, they still stress them. That stress causes them to produce free radicals, says James Collins, a biomedical engineer at Boston University and one of the paper’s authors.

Those free radicals are produced by oxidation, a process that’s known to damage cells. In the case of bacteria, the free radicals damage the bacteria’s DNA, causing some of the affected bugs to mutate.

Two and a half years ago Collins’ group began looking at how bacteria respond to antibiotics. It was then that they discovered that antibiotics can stimulate the pathways that create free radicals in bacteria.

A year ago they started considering what other implications their discovery might have.

“We wondered whether sub-lethal levels still produce free radicals. We know the cells wouldn’t die, but we know that free radicals can damage DNA, and that increases mutenigenesis,” he says.

And that’s exactly what they found. Basically, if the antibiotic dose isn’t high enough to kill every bacteria in sight, “you could be creating a zoo with a wide range of mutations,” he says.

The  finding is important “within the context of our understanding — or lack of understanding — of how bacteria become resistant to antibiotics,” says Deborah Hung, a molecular biologist at Massachusetts General Hospital, who wrote an accompanying Perspective piece on the article.

The  truth is that no one really knows exactly how bacteria become resistant to antibiotics, says Hung. So knowing that low levels of antibiotics might potentially increase the random chance that bacteria might mutate into resistant forms could have important implications for medicine.

By Elizabeth Weise

DNAWellnessinfo.com Resource:  http://content.usatoday.com/communities/sciencefair/post/2010/02/a-new-theory-of-how-low-doses-of-antibioitics-create-antibiotic-resistance/1

Stem Cell Research Makes Another Advance

February 8, 2010 – health Day

MONDAY, Feb. 8 (HealthDay News) — Scientists say they’ve developed a new and easier way to create what’s known as pluripotent stem cells

— cells that can develop into one of many cell types for use in regenerative medicine.

Unlike many other methods, this new technique doesn’t use viruses to introduce genes into cells or permanently alter a cell’s genome. Instead, tiny circles of DNA are used to transform stem cells taken from human fat into induced pluripotent stem cells, which are the starting point for research into many human diseases.

This is the first time that adult (non-embryonic) stem cells have been reprogrammed this way and it could be an important advance toward the use of such cells in humans, according to the Stanford University School of Medicine researchers.

“This technique is not only safer, it’s relatively simple,” study co-author Dr. Michael Longaker, a professor of surgery and deputy director of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine, said in a Stanford news release. “It will be a relatively straightforward process for labs around the world to begin using this technique. We are moving toward clinically applicable regenerative medicine.”

The researchers plan to create pluripotent stem cells to learn more about, and perhaps some day treat, human heart disease.

“Imagine doing a fat or skin biopsy from a member of a family with heart problems, reprogramming the cells to pluripotency and then making cardiac cells to study in a laboratory dish. This would be much easier and less invasive than taking cell samples from a patient’s heart,” study senior author Dr. Joseph Wu, an assistant professor of cardiology and radiology and a member of Stanford’s Cardiovascular Institute, said in the news release.

The study was published online Feb. 7 in the journal Nature Methods.

More information

The U.S. National Institutes of Health has more about stem cells.

DNAWellnessinfo.com Resource:  http://www.usnews.com/health/managing-your-healthcare/womens-health/articles/2010/02/08/stem-cell-research-makes-another-advance.html

Living fast? Scientists show lifespan is linked to DNA

Ian Sample, science correspondent
guardian.co.uk, Sunday 7 February 2010 19.55 GMT

Scientists have isolated a gene sequence that appears to determine how fast our bodies age, the first time a link between DNA and human lifespan has been found.

The discovery could have a profound impact on public health and raises the best hope yet for drugs that prevent the biological wear and tear behind common age-related conditions such as heart disease and certain cancers.

The work is expected to pave the way for screening programmes to spot people who are likely to age fast and be more susceptible to heart problems and other conditions early in life. People who test positive for the gene variant in their 20s could be put on cholesterol-lowering statin drugs and encouraged to exercise, eat healthily and avoid smoking.

The breakthrough is unlikely to lead to drugs that dramatically extend lifespan, but doctors say it may help prolong the lives of patients whose genes make them susceptible to dying young.

The research gives the kind of insight into the biology of ageing that has not emerged from work on other strategies that claim to extend lifespan, such as consuming vast quantities of antioxidants or pursuing a severely calorie-restricted diet.

“This may help us identify patients who are at a greater risk of developing common age-related diseases so we can focus more attention on them,” said Professor Nilesh Samani, a cardiologist at the University of Leicester, who led the research.

The research highlights the difference between chronological age and biological age, the latter of which is determined by our genetic makeup and lifestyle factors, such as diet and smoking. Two people of the same age can have biological ages that differ by more than 10 years.

A team led by Samani and Professor Tim Spector at King’s College, London found a common sequence of DNA was strongly linked to a person’s biological age. In a study of nearly 3,000 people, around 38% inherited one copy of the gene variant and were biologically three to four years older than those who did not carry the sequence.

A minority of 7% inherited two copies of the DNA sequence and were on average six to seven biological years older. The majority of the population, 55%, do not carry any copies of the variant.

The study, published in the journal Nature Genetics, was prompted by the huge variability in the age at which people develop medical problems that are often considered diseases of the elderly.

“I see patients in their 80s with high blood pressure who have healthy coronary arteries and I see people in their 40s who don’t seem to have any risk factors yet have advanced heart disease,” Samani said. “We think this kind of variability must have something to do with premature ageing.”

Most of the cells in our bodies contain long molecules of DNA called chromosomes that have protective caps at either end called telomeres. Every time a cell divides, the telomeres shorten, like plastic tips fraying on a shoelace. When the telomeres become very short, the cell starts to malfunction and show signs of ageing.

From blood samples, Samani and Spector found a particular gene sequence was more common in people who had unusually short telomeres for their age. The section of DNA was found on chromosome three, next to a gene called TERC, which makes an enzyme that repairs telomeres when they shorten.

People who carry one or two copies of the genetic sequence probably make less of the enzyme, called telomerase, when they are growing in the womb. This means they are born with shorter telomeres, and so are prone to ageing more quickly.

“The effect may be built in at a very early stage in life. If you’re born with shorter telomeres, there’s evidence you will be prone to heart disease and other age-related diseases,” Samani said.

Scientists are unlikely to reverse the ageing process by boosting telomerase in people’s bodies. Telomerase is almost completely deactivated after birth, but is switched back on in cancer cells so they can divide endlessly without dying. “Introducing telomerase might protect you from heart disease, but if you turn it on willy nilly you could cause cancer instead,” Samani said.

DNAWellnessinfo.com Resource:  http://www.guardian.co.uk/science/2010/feb/07/ageing-genetics