Researchers are developing controversial early screening procedures
Genetic impairments in children can already be identified in the womb with the help of an amniotic fluid analysis. However, the procedure is extremely controversial, not least because the corresponding intervention entails a considerable risk. In the worst case, miscarriage threatens. However, researchers at the University of Washington at Seattle have now developed a new, non-invasive procedure that is intended to enable full genome sequencing.
The scientists led by Jacob O. Kitzman and Jay Shendure use the blood of the mother and the saliva of the father for the "non-invasive prenatal genetic diagnosis" of the fetuses. Accordingly, the health risk of the examination is minimal. However, this type of early detection of genetic changes, such as trisomy 21 (Down syndrome), remains ethically controversial. Because critics assume that the number of abortions would increase significantly with improved early detection. Here, the natural reproductive process is interfered too far, according to the accusation of opponents of prenatal diagnosis.
New procedure with clear advantages over amniotic fluid examinations Compared to the amniotic fluid examinations practiced so far, the new diagnostic method of the US researchers is undoubtedly a significant improvement. This form of prenatal diagnosis excludes direct health risks for the unborn child. Scientists at Washington University in Seattle used "sequencing the genome of both parents" to analyze the genetic makeup of the fetus. They took a blood sample from a woman in the 18th week of pregnancy and looked for haploid (simple chromosome sets) DNA sections. From previous studies it was already known that corresponding DNA pieces of the child can be detected in the mother's blood plasma. The US researchers used the DNA sections found and combined them with the father's genome, which was sequenced using saliva samples, to analyze the genetic makeup of the fetuses. Based on statistical calculations, Jay Shendure and colleagues were able to determine the genome sequence of the human fetus relatively precisely. When compared to the umbilical cord blood taken later, it was found that "inheritance was predicted with 98.1 percent accuracy", the US researchers write in the article "Non-invasive complete genome sequencing of a human fetus".
Spontaneous gene mutations were also predicted relatively reliably. When comparing the statistically calculated and the actual fetal genome sequence, the researchers found that "39 out of 44 de novo point mutations were detected in the fetal genome". The accuracy of the new prenatal diagnostic procedure was relatively high, also with regard to possible spontaneous mutations in the child's genome. The human geneticist and medical ethicist Wolfram Henn from the Saarland University explains to the news agency "dpa" that the US researchers' current research results state that this is "a thunderbolt and changes the perspective of prenatal examinations fundamentally." The researchers led by Jacob O. Kitzman and Jay Shendure would have provided the proof "that in principle it is technically possible to determine all of a person's genetic information before birth without touching the child," continued Wolfram Henn. A corresponding analysis also makes it possible to discover "hidden systems that can only lead to the potential occurrence of hereditary diseases in the next but one generation," explained the human geneticist.
Reliable early detection of hereditary diseases Although the US researchers admit that “technical and analytical challenges” to ensure reliable predictions remain with the new diagnostic method, they expect “the non-invasive analysis of hereditary variation and de novo mutations in fetal Genomes will greatly facilitate the prenatal diagnosis of recessive and dominant Mendelian diseases ”in the future. Wolfram Henn also emphasized that the test still had to be “solid”. If successful, however, this could enable a reliable prediction of thousands of inherited diseases, such as Pätau syndrome (trisomy 13), Edwards syndrome (trisomy 18) or various metabolic diseases (e.g. cystic fibrosis). A total of over 3,000 so-called monogenetic disorders are known, with about one percent of newborns showing corresponding changes in the genome, the US researchers report.
Ethical controversy about the prenatal diagnostic procedures However, the ethical controversy is by no means over with the development of the new prenatal diagnostic procedure, but could become even more acute in the future if this early examination method is used more frequently. Here, the human geneticist Wolfram Henn also sees politics as being obliged to address the ethical aspects of the new technical possibility. "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 entire genome of their child before birth," explained Henn. Because a human selection of the survivable fetuses is also extremely controversial in the professional world. So far, there has been no clear answer to the question of who can get what information on the genetic makeup of the fetus at what time, Henn explained. (fp)
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