Genome analysis
A cheap method of DNA analysis has been created
Alexander Bulanov, Izvestia
The new method of DNA analysis will simplify and double the cost of diagnosing genetic diseases, and will also give doctors the opportunity to find new types of disorders. Moreover, the technology will be relevant both in the treatment of people and for the selection of embryonic cells that are used in the IVF procedure. This will allow couples with genetic disorders to have healthy offspring. The technique has already been tested on cells and has been used in a test mode to diagnose diseases in a group of patients. It is expected that the clinical use of the technique may begin in 2021.
A tangle of genes
The main goal of doctors involved in the diagnosis of genetic diseases is to identify violations in the patient's DNA chain, which contains all the information about his body. Moreover, different diseases are characterized by different genome changes. For example, a significant part of them is caused by point mutations affecting only a few nucleotides that make up the gene (for example, this often happens with cystic fibrosis). In other cases, there is a larger problem associated with a defect in a large segment of several genes – in particular, doctors observe a similar picture with Down syndrome, in which the disorder affects the whole chromosome.
As a rule, doctors begin to look for the root causes of the disease with the largest and most noticeable changes – for example, with the help of a microscope, they can examine DNA at the chromosome level. If this method does not help, then the patient is sent to other studies, implying a targeted study of individual genes. Thus, in practice, tests are used sequentially (as their accuracy and selectivity increase) until the cause of the disease is detected. However, this approach often turns out to be too expensive for the patient, since sometimes you need to pay from 10 to 50 thousand rubles for one procedure.
To simplify and reduce the cost of the diagnosis process was proposed by Russian scientists who used technologies that were previously used only for scientific research.
– In our work, we use the method of fundamental biology, which allows using sequencing (reading – Izvestia) DNA to determine its spatial position in the cell nucleus, – said Veniamin Fishman, a leading researcher in the sector of genomic mechanisms of ontogenesis at the Institute of Cytology and Genetics SB RAS. – At the same time, physically close sections of DNA in our experiment are stitched together, and we can detect this by sequencing.
According to the scientist, it is these DNA cross–links formed during the biochemical reaction that make it possible to judge the genome by evaluating its structure selectively - in key segments, after reading which it is possible to judge the state of larger DNA sections without going into their detailed study. As a result, this can halve the cost of analysis.
Healthy inheritance
The introduction of technology can also open up completely new medical prospects.
– We can find the genetic causes of defects in the intellectual and physical development of a child only in 15-20% of cases – this indicates that there are levels of DNA organization that cannot be adequately analyzed by methods used in modern medicine, – explained Igor Lebedev, Deputy Director for Scientific Work of the Research Institute of Medical Genetics of the Tomsk National Research Medical Center. – Studying the spatial position of DNA in cells can change this situation, allowing us to find violations in people who have previously failed to diagnose.
According to the expert, the technology can also be applied before the artificial insemination procedure, which will allow doctors to select only those embryonic cells that do not have genetic disorders. As a result, a healthy child will be born in a family with a risk of transmission of hereditary diseases.
Scientists have already entered the stage of testing the technology.
– The new diagnostic method has been successfully tested on tumor cells, which we use as a model due to the large number of predictable mutations found in them, - said Veniamin Fishman. – So far, the technology needs some improvements, but our forecast is optimistic.
The new development was evaluated at the V.A. Engelhardt Institute of Molecular Biology (IMB) of the Russian Academy of Sciences.
– The proposed research method can really simplify diagnostics and reduce its cost, – says Anna Kudryavtseva, a leading researcher at the IMB RAS. – It can also allow to detect disorders that are not yet determined by standard methods, in particular, diseases associated with balanced rearrangements in which a segment of the chromosome moves to an unusual place for it.
Now scientists have already started using the method to diagnose diseases in the first eight patients with various genetic disorders. If positive results are obtained next year, their number is planned to increase to 50, after which the technology will be able to switch to medical practice. There are chances that this will happen already in 2021.
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