DNA hunting. A pregnant woman undergoes an amniocentesis for fetal cells.
Yoav Levy / MedNet / Corbis
A baby could have the eyes of his mother, but the mother's DNA in the child's blood, less during pregnancy. Researchers have now used this DNA test for genetic diseases before birth. The technique could enable doctors to perform prenatal screening from only one of the mother's blood sample.
diagnosisprenatal check for chromosome abnormalities and genetic diseases is common. Doctors capturing fetal cells for DNA analysis using amniocentesis, which draws some of the fluid in the womb, or chorionic villus sampling, which picks a placental tissue extract. Of course, both tests slightly raise the chances of miscarriage, prompting researchers to seek alternatives. In 1997, chemical pathologist Dennis Y. Lo, now at the Hong Kong Chinese University, and his colleagues discovered a rich vein of fetal DNA, well, the veins of the mother. About 10% of the DNA fragments floating in the blood of the mother is from the fetus to die placenta or fetal cells. Clinical tests capitalize on this DNA to detect the baby's gender and whether the mother and child have incompatible Rh blood groups, which can lead to fatal complications. But the difficulty of distinguishing the maternal DNA to fetal DNA has prevented researchers to develop tests for testing for most other genetic diseases.
To overcome this problem, Lo and colleagues applied advanced DNA sequencing techniques, which can quickly sequence large amounts of DNA, billions of DNA fragments into a blood sample from a pregnant woman. Using DNA samples from a woman and her husband, the team analyzed 00,000 single nucleotide polymorphisms, change a letter in the genetic code that reveal where the DNA of the parents differs. With this information, researchers first determined that the blood of the mother carries the whole genome of the fetus and the baby DNA inherited from each parent.
The team then tested the approach on a pregnant woman in an obstetrics clinic. The woman and her partner each carried a defective copy of the gene for part of hemoglobin, which predispose the fetus to ß-thalassemia, which can lead to severe anemia. The team tests showed that the baby did not ß-thalassemia, but was a carrier, receiving a mutated version of the gene from the father and a normal mother. Analysis of the DNA of the baby obtained by chorionic villus sampling, whose mother had also suffered, confirmed the diagnosis. "We worked on the principle and made the first non-invasive genetic analysis of a fetus from the mother's blood," said Lo, whose team presents its findings online today in Science Translational Medicine .
Several obstacles stand in the way of widespread use of analysis of fetal DNA, however. On the one hand, the type of DNA sequencing used in the study is too expensive for clinical trials, although most researchers believe the cost to fall in the coming years. The results are also very complex and difficult to interpret, notes geneticist Diana Bianchi reproduction of the Tufts School of Medicine at Boston University. "It is a brilliant proof of concept study, but it is not ready for clinical application."
Yet many researchers are impressed. "I think it's a beautiful piece of work," says molecular geneticist Arthur Beaudet of Baylor College of Medicine in Houston, Texas. "It is an important step in the direction to show the ability of this approach," adds Mark Evans, an obstetrician gynecologist and geneticist at the School of medicine Mount Sinai in New York City. molecular biologist Sinuhe Hahn university women Hospital in Basel, Switzerland, says that the approach should allow fetal DNA tests for a variety of other genetic diseases such as cystic fibrosis and Tay-Sachs disease. "in essence, you have the whole genome of the fetus for you."
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