New early detection of diseases in fetuses

Researchers are developing controversial procedure of early examination

07/06/2012

Genetic impairments of children can already be detected in the womb with the help of an amniotic fluid analysis. However, the procedure is extremely controversial, not least because the intervention entails a considerable risk. In the worst case, a miscarriage is imminent. However, researchers at the University of Washington at Seattle have developed a new, non-invasive method to enable complete genome sequencing.

The scientists around Jacob O. Kitzman and Jay Shendure use for the „non-invasive prenatal genetic diagnosis“ the fetuses the mother's blood and the father's saliva. Accordingly, the health risk of the examination is minimal. However, this type of early detection of genetic alterations, such as trisomy 21 (Down syndrome), remains ethically controversial. Because critics assume that the number of abortions with improved early detection would increase significantly. Here too extensive intervention in the natural reproductive process, so the charge of opponents prenatal diagnostics.

New method with clear advantages over amniocentesis
Compared to the amniocentesis study hitherto practiced, however, the new diagnostic procedure of the US researchers is undoubtedly a significant improvement. Direct health risks for the unborn child are excluded in this form of prenatal diagnosis. The scientists of Washington University in Seattle have „sequencing the genome from both parents“ used to analyze the genotype of the fetus. They took a blood sample from a woman in the 18th week of pregnancy and searched for haploid (simple chromosome set) DNA sections. From previous studies it was already known that in the mother's blood plasma, corresponding DNA pieces of the child can be detected. The US researchers used the DNA fragments found and combined them with the genome of the fathers sequenced using saliva samples to analyze the genotype of the fetuses. Based on statistical calculations, Jay Shendure and colleagues were able to determine the genome sequence of the human fetus relatively accurately. When compared with the umbilical cord blood taken later, it was found that the „Inheritance predicted with 98.1 percent accuracy“ was, the US researchers write in the article „Noninvasive 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 too „39 of 44 de novo point mutations detected in the fetal genome“ were. Thus, the accuracy of the new prenatal diagnostic procedure was also relatively high in terms of possible spontaneous mutations in the genome of the child. The human geneticist and medical ethicist Wolfram Henn of the University of the Saarland explained in the light of the current research results of US scientists to the news agency „dpa“, this is „a thunderclap and fundamentally changes the perspective on prenatal examinations.“ The researchers around Jacob O. Kitzman and Jay Shendure had provided the proof, „that in principle it is technically possible to determine all the genetic information of a human before birth, without touching the child“, Wolfram Henn continues. A corresponding analysis also makes the discovery possible, „Covert plants that can only lead to the potential occurrence of hereditary diseases in the generation after next, "explained the human geneticist.

Reliable early detection of hereditary diseases
Although the US researchers acknowledge that „technical and analytical challenges“ to ensure safe predictions in the new diagnostic procedure, but they expect it, „that the non-invasive analysis of hereditary variation and de novo mutations in fetal genomes, the prenatal diagnosis of recessive and dominant Mendelian disease“ significantly easier in the future. Wolfram Henn also emphasized that the test, however, is still to come „solid“ must prove. However, if successful, this could provide a reliable prediction of thousands of hereditary diseases such as the Pätau syndrome (trisomy 13), Edwards syndrome (trisomy 18) or various metabolic diseases (eg cystic fibrosis). Overall, more than 3,000 so-called monogenic disorders are known, with about one percent of newborns having corresponding changes in the genome, the US researchers report.

Ethical controversy surrounding prenatal diagnostic procedures
However, the ethical controversy with development of the new method of prenatal diagnostics is by no means over, but could increase significantly in the future with increased use of this early method of investigation. Here, the human geneticist Wolfram Henn sees politics as having the duty to devote himself to 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 their entire genome before birth“, explained Henn. For a human selection of the surviving fetuses is also extremely controversial in the professional world. So there is no clear answer to the question of who should receive which information about the genetic material of the fetus at what time, explained Henn. (Fp)

Also read:
Mother coins unborn child
Negative conclusion after 10 years of stem cell research

Image: Dieter Schütz