By Janet Fang
Posting in Science
The next generation of sequencing the next generation? Scientists have developed a way to scan a baby's entire genome while in the womb, without having the mother undergo invasive prenatal screening.
A mother-to-be can one day learn about her unborn baby’s risk for genetic diseases without a large needle piercing her womb.
Using just a tiny sample of the mother’s blood, this new technique can scan the fetus’s entire genome – picking up indications of congenital diseases like cystic fibrosis and sickle-cell anemia and pretty much everything there is to know about the baby’s genetic make-up.
Traditionally, prenatal testing for genetic diseases requires amniocentesis -- taking a fetal tissue sample, either from the placenta or fluid in the womb, which can harm the fetus, however slightly (although, 1% of these procedures result in miscarriage).
Over a decade ago, chemical pathologist Y. M. Dennis Lo from the Chinese University of Hong Kong discovered fetal DNA floating in pregnant women's plasma – the yellowish liquid where blood cells are suspended. That discovery has since led to noninvasive, but limited, prenatal screening for certain diseases like Down syndrome and specific genetic characteristics, such as blood type.
But, the baby’s floating DNA is mixed in with the mom’s – making up only 10% of the total mix. On top of that, all the DNA molecules in the plasma are short broken fragments. “Imagine millions of jigsaw puzzle pieces and then put in 10 times as many pieces from another jigsaw and you try to assemble the first one,” Lo says.
As verification, the researchers recruited a couple that wanted prenatal testing for an inherited and possibly fatal type of anemia called β-thalassemia. Both parents carry the mutation.
Using blood from the pregnant woman, the team sequenced billions of DNA molecules, and navigated their way using genetic maps of the mother and father. The fetus, they revealed, had inherited the mutation for the blood disease from the father, but without a faulty one from the mother, the child will only be a carrier for the disease.
The study was published in Science Translational Medicine on Wednesday.
Several obstacles, however, prevent the widespread use of this new technique. For one, the type of DNA sequencing they used is too expensive for clinical testing, although most researchers expect its cost to plummet in the next few years.
At the moment, the three-week-long procedure would cost about $200,000 per case. "Cutting costs will be very important," says Lo. While sampling the entire fetal genome may remain prohibitively expensive for some while, Lo hopes within a year to develop a test focused on about five important genetic conditions.
“For any particular family you want to screen, there are only a handful of genes that are clinically important,” Lo says. These targeted tests focus in on disease-causing genes and could be 50 to 100 times cheaper, he adds.
Dec 8, 2010
Just think! A complete generation of blonde, blue eyed, atheletic children with a marked propensity to raising their right arms in a salute to their benificent leader...
Thanks, IMWeira, It partly answers my question. We've known for a while that our children are somewhat shaped by the genes they inherit from us. I'm not sure what the difference is between "genome" and "chromosone." But what if, by having children, a woman is also somehow, even a little bit, shaped by each child?
Back in the 70's when I was doing the mommy thing I had a doctor tell me that y chromones from the male babies would show up in my blood for years after I had them. Presumably x chromones would too but be unnoticed as I had plenty of my own xx's running around. I always wondered how that played out with further developments in dna testing after the ability to rapidly sequence dna came out. Now I know, broken chains in bits and pieces do not resemble the intact parental gene sequence. Does that answer the question rmberkiowitz?
This has super interesting implications. I wonder if this will ultimately lead to a selective evolution where most people choose to abort fetuses that are carry a gene for a certain type of disease.
How long does the baby's genome stay in the mother's blood? Is it only until delivery or shortly afterwards, or is it permanent? Does a mother carry around her baby's genome for the rest of her life? That could have some interesting implications.