Entries in Genome (3)


New Baby Genome Mapping to Detect Disorders in the Womb?

Stockbyte/Thinkstock(SEATTLE) -- A new, noninvasive procedure may one day allow women to test their unborn babies for more than 3,500 genetic disorders. It could perhaps replace amniocentesis, in which a probe is inserted through a woman’s abdomen, extracting a small amount of amniotic fluid to test for abnormalities in the fetus.

Scientists at the University of Washington took blood samples of a woman who was 18 weeks pregnant, and saliva from her partner to map the fetus’s DNA. The method was then repeated in another couple.

They then reconstructed the genetic code of the unborn baby, then tested the accuracy of the results by using umbilical cord blood after the baby was born.

“The primary significance of this is that…it may broaden the availability of genetic screening to more patients, while at the same time screening for much larger panels of disorders than can currently be detected,” said Jacob Kitzman, lead author of the study.

The new procedure can test for, among thousands of diseases, spina bifida and Down syndrome, the most common genetic disorders in the U.S., and is safer than amniocentesis.

“This is an incredible breakthrough with huge ethical implications,” said Art Caplan, a professor of medical ethics at University of Pennsylvania Medical Center.

Caplan said today’s amniocentesis testing was relatively “crude,” and new advances would allow more people to obtain reliable genetic information about their children.

Miscarriage is the primary risk of amniocentesis -- the uterus can become infected, the water can break or there’s premature labor.  The risk of miscarriage ranges from one in 400 to one in 200.

About 200,000 amniocentesis procedures are performed every year in the U.S., according to the Mayo Clinic, but “with accurate testing that poses no risk, this new form of genetic testing is likely to be offered to every women and family who is pregnant if the cost is low,” said Caplan.

While researchers said they don’t believe these findings will have an impact on genetic test in a clinical setting in the immediate future, they hope follow-up work will bring technical and methodological improvements that will allow for an easier-to-apply, more accurate and less costly version of the test.

When the time comes for the procedure to be used in a clinical setting though, Kitzman said clinicians would face the challenge of interpreting these results and communicating them with expectant parents -- both the results themselves and the uncertainties that come with them.

While these advances will help better understand risk factors for illness, Caplan predicted “they will be among the most controversial forms of testing ever to appear in medicine as the debate over abortion and disabilities both shift to whole genome genetic testing.”

While the ethical questions that have always surrounded prenatal testing will not disappear with the new procedure, Kitzman said the “noninvasive tests may provide some advantage by posing less potential risk to the fetus.”

"In my experience, full information for parents permits ethical decisions for a family,” said Dr. F. Sessions Cole, professor of pediatrics at Washington University School of Medicine at St. Louis. "A longer term ethical issue concerning the ability to predict disease development in later childhood or adulthood from fetal DNA will also need to be addressed. Hopefully, this new information will prompt development of nutritional, pharmacologic, behavioral, environmental, and other strategies to reduce genetic disease risk.”

Copyright 2012 ABC News Radio


The Short Answer on Pygmy Height? Genes

Comstock/Thinkstock(PHILADELPHIA) -- Why do we walk on two legs instead of crawling around on all fours?  Why are sons so often taller than their fathers?  And why are pygmies so short?

It is human to ask these questions, and the answers can sometimes be found in the smallest places.

Researchers from the University of Pennsylvania announced on Thursday that they may have discovered why pygmies are short -- and the answer lies in the footprints of natural selection in the human genome.

Pygmy tribes are found all over the world and represent the largest group of mobile hunter-gatherers.  Pygmies are unusual in that their average height is a meager 4 feet, 11 inches.  They grow up just like other humans until they become teenagers, at which point they typically fail to undergo a normal growth spurt. Their short stature mirrors their short lifespan, with average life expectancy a mere 17 years.

These tribes have captured the interest of social scientists and biological researchers who, for years, have tried to understand why pygmies diverged from the norm. Theories on their short stature have ranged from suggestions that it was a natural adaption to their difficult lifestyle, to the notion that the thick forest kept them away from sunlight, decreasing vitamin D and leading to low calcium levels and slow bone growth.

More recently, it has been suggested that, due to their short life-span, the bodies of pygmies have evolved to shunt energy originally devoted to growth, in favor of efforts towards early reproduction.

But in the new study, published in the journal PLoS Genetics, researchers for the first time were able to apply new genetic tools to address this question -- and it looks like genes could hold the answer.

The researchers not only found genes linked to pygmy height, but they also found that those same genes are implicated in reproductive hormone activation and immune system function -- providing some explanation to how the trait has survived for 2,800 years.

“The truth is we don’t know where pygmies came from,” said lead researcher Dr. Sarah Tishkoff, associate professor of genetics and biology and the University of Pennsylvania.  “By looking at a million genetic variants across the genome, we finally have a good understanding of their ancestry.”

Tishkoff notes that pygmies’ genomes are a veritable toolbox that allows them to take on their challenging existence. They found that a gene associated with height was also linked to oxytocin, the hormone responsible for nipple stimulation and breast feeding in women, linking it to the theory of early reproduction and species preservation in such short-lived people.

Another gene, linked to bacterial resistance and immune function, also happened to shut down the actions of human growth hormone in the pygmies’ bodies.

“Everything is intricately linked,” Tishkoff said.  “As evolution is tinkering with one of these systems, others are affected as well.”

Tishkoff says she studies pygmy genes because she is interested in the science behind human adaption -- the what, when, where and why of human origins.

And while these findings certainly help us understand why a pygmy is shorter than the average Joe, they also show us how humans have adapted to their environments over time -- information that may help the rest of us adjust appropriately to our own futures.

Copyright 2012 ABC News Radio


Extreme Gene Testing: One Researcher’s Experience

Comstock/Thinkstock(STANFORD, Calif.) -- When you look at 56-year-old scientist Dr. Michael Snyder, it’s unlikely that “diabetes” would be the first word to come to mind.

“I don’t look like the type of man who has diabetes,” he said. “I have a thin frame and stay active.”

Based on his appearance, most other doctors would agree. However, Snyder’s first-of-its-kind research, through which he subjected himself to frequent lab tests over a period of more than a year, revealed that he did, in fact, have the condition -- and it allowed him to confront it earlier rather than later.

But it also afforded him a rare opportunity: to see the link between his genes and illness play out right before his eyes.

Snyder and colleagues at his lab at Stanford University have spent the past 14 months sequencing his genome -- frequently -- and following the changes in his health. He discovered his personal risk for developing type 2 diabetes, heart disease, a lethal blood disorder and skin cancer.  He saw his genome change in response to viral attacks on his body, including the development of diabetes after catching a respiratory virus from his children.

When Snyder noticed changes in his genome consistent with diabetes, he alerted his personal physician, who was skeptical at first. Laboratory testing, however, revealed an elevation in his blood sugar that lasted several months.

He changed his diet -- cut out sugary desserts, began exercising more frequently, and eventually lost 15 pounds. In his lab, these changes were evident in his genome, and on re-check at his doctor’s office, his diabetes was gone.

Snyder discovered other interesting ways to apply his personal genome monitoring to his own health. He figured out on his own the dosage he needed of his cholesterol-lowering medications based on his personal sequencing of liver proteins. He was able to draft a lineup of dosages for other medications, too, including the anti-diabetes medication he anticipated he needed.

It is easy to see how many in the general public might be interested in emulating Snyder’s approach. However, Dr. F. Sessions Cole from St. Louis Children’s Hospital warns that Dr. Snyder’s response to infection or development of type 2 diabetes may not be appropriate to apply to others -- at least not yet.

“Applicability to the general public will require larger studies to determine patterns,” he said.

For now, Snyder will continue to sequence his own genome regularly, following the hidden changes in real time.  He avoided developing complications from diabetes because of this monitoring. Before his study began, he saw his personal physician once every three years for a check-up.

“If I hadn’t seen the diabetes in my genome,” he said, “I wouldn’t have known it was there.”

Copyright 2012 ABC News Radio

ABC News Radio