They see this as a step toward testing for thousands of diseases caused by alterations in a single gene – without endangering the child through invasive methods such as amniocentesis in the womb. The team from the university of washington in seattle presents the results in the journal "science translational medicine.
"This is a thunderclap and fundamentally changes the perspective on prenatal testing," said human geneticist and medical ethicist prof. Wolfram henn from the university of saarland told the german press agency dpa. According to the article, there are more than 3,000 disorders caused by the alteration of a single gene. Taken individually, they are rare, but in total they affect about one percent of all newborns. Cystic fibrosis, for example, is one of the most serious diseases.
It is now up to policymakers to address the ethical issues surrounding this technical possibility, henn said. The publication had been expected in the professional world. "From a technological point of view, it is the holy grail of genome analysis, but from an ethical point of view, it is very problematic to reveal to parents the complete genome of their child before birth."
The scientists led by jay shendure and jacob kitzman had given an expectant mother around 18./19. A blood sample is taken from the mother at the second week of pregnancy and a saliva sample is taken from the father. They searched for free DNA sticks of the child in the mother’s blood. It has been known for a long time that such genetic snippets are floating around in the mother’s body before birth.
Other tests are also taking advantage of this fact, and a screening for trisomy 21 (down syndrome) is also to be launched in germany. The test determines whether three instead of two copies of chromosome 21 are present. Until now, this has been possible by taking cells from the amniotic fluid through the pregnant woman’s abdominal wall – with the risk of miscarriage. The new test is intended to complement pranatal diagnostics in high-risk pregnancies.
Shendure and kitzman used statistical methods to draw conclusions about the entire genome of the fetus and later compared their results with the genome in the umbilical cord blood of the newborn. They repeated the procedure on another couple at an earlier stage of pregnancy. The scientists also analyzed which genetic variants were transferred from the parents to the child and which must have developed through spontaneous mutations. According to the data, they discovered 39 of 44 new mutations when the child was still a phototype.
"The publication is proof that it is in principle technically possible to determine all of a person’s genetic information even before birth, without harming the child," said henn. "Including hidden predispositions that can lead to the potential emergence of hereditary diseases only in the next generation"."It remains to be seen whether the test is "sound". But experience has shown that such procedures have become faster, more reliable and less expensive. The authors themselves admit that the method still needs to be improved.
"And then the question arises, which will reach into the political arena: who is allowed to receive which genetic information at what point in time – not only about disease predispositions that are already significant in childhood, but also about diseases that only appear later, such as hereditary colon cancer, or even traits without disease value, for example athleticism? We do not yet have adequate answers to these questions," henn explained.
Henn is a member of the central commission for the safeguarding of ethical principles in medicine and its border areas of the federal medical association. The german ethics council is currently preparing a statement on the future of genetic diagnostics on behalf of the federal government.