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Scientists from Moscow State University have checked whether fetal DNA diagnostic systems work
Molecular biologists from Moscow State University compared popular systems for isolating DNA fragments from the blood of pregnant women and showed that they can really be used to search for developmental disorders in the fetus. Their findings were published in the journal Molecular and Cellular Probes.
"We found out why many researchers mistakenly thought that these kits were equally effective. Determining the optimal set for fetal DNA isolation will not only improve its quality, but will also serve as an impetus for the development of new approaches for diagnosis," says Mark Jain, a student of the Faculty of Fundamental Medicine of Moscow State University.
Scientists and doctors have known for several decades that fragments of DNA and proteins of the embryo often "escape" through the placenta into the mother's body and accumulate in her bloodstream in sufficiently large quantities. This makes it possible to diagnose many severe genetic diseases even before the birth of a child and protect it from their development.
In recent years, biotech and pharmaceutical companies have created several different versions of genetic tests for such diagnostics, whose effectiveness, as Jain notes, was not evaluated specifically on fetal DNA samples. At the same time, most doctors consider them equally effective.
Russian molecular biologists have made up for this shortcoming by comparing the quality of the two most popular extracellular DNA analysis systems, DSPVK and CNAK, created by the European company Qiagen.
To test it, they collected blood samples from 18 pregnant women in the first stages of fetal development and dozens of their peers who were not carrying a child. Using these toolkits, the researchers isolated extracellular DNA from these samples and checked how many fragments of the fetal genome were present in it.
To do this, scientists have created their own set of various analytical techniques that allowed them to separate maternal DNA from its embryonic "cousin", as well as from traces of the presence of viruses, bacteria and other foreign organisms in the woman's body.
This became possible due to the fact that the number of special molecular labels on the surface of "adult" and embryonic DNA is quite different. The fact is that when an egg and a sperm merge, all such structures, the so-called methyl tags, are removed from the genome, and appear in the same amount only closer to the birth of a child.
Such differences, as scientists say, can be used to isolate embryonic DNA from maternal blood, using special enzymes that recognize such tags and destroy the molecules carrying them. Using one of these substances, BstFN I, Russian biologists estimated the amount of fetal DNA "caught" by DSPVK and CNAK.
As it turned out, both systems could capture fragments of the genome of the unborn child in sufficient quantities for analysis, but they did it with very different efficiency. On average, CNAK captured twice as much of both germinal and parental DNA, and the proportion of the former in the total mixture was noticeably higher than when working with DSPVK.
On the other hand, as scientists emphasize, the second diagnostic technique is about three times more expensive than its more advanced competitor. Therefore, its use in most cases, when high accuracy of analysis is not required, will be more rational both from the point of view of doctors and their patients.
According to the press service of the university, Mark Jain and his colleagues, working on this project, also created a new way to diagnose Down syndrome, which can be carried out in a similar way in the ninth week of pregnancy. An application for patenting a new method is already under consideration by the relevant authorities.
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