The increasing number of couples trying to have children are concerned about the health of their future babies. The risk of occurrence of fetal genetic defects increases in women who get pregnant in their mature age, in persons with the diagnosed genetic burden in their family history and in infertile couples. The scientists from the INVICTA Clinic have developed a solution, unique in Europe, which uses the next-generation DNA sequencing and which will allow dealing with this problem.
The PGD NGS method (preimplantation genetic diagnosis with next-generation sequencing) uses the most up-to-date techniques of human genome sequencing for testing embryos. It may be used as a part of in vitro fertilization and provides comprehensive information concerning embryo’s DNA with regard to diseases or genetic mutations. It provides physicians with a unique opportunity to help couples who are exposed to an increased risk of genetic abnormalities in the foetus. This is the first solution of this kind in the world.
Until now, in case of appropriate indications, it has been possible to perform the preimplantation genetic testing, PGD, using the FISH technique or microarrays (e.g. aCHG). Both these techniques are effective, but they have their limitations. The most important relates to the scope of testing – the physicians have to know exactly what diseases or mutations are the target of testing. Now – thanks to the PGD NGS method – it is possible to perform the comprehensive analysis of the parents’ DNA and then the testing of the embryo and excluding the diseases resulting from chromosomal abnormalities (e.g. Down or Patau syndrome) as well as single-gene diseases in a single test.
What is PGD NGS?
PGD NGS is used as a part of in vitro procedure. Following the oocyte fertilisation, the material for testing is collected from embryos after 3 days or in blastocyst stage. This material is transferred to the INVICTA genetic laboratory where it is prepared and analysed with the use of a special apparatus, PGM (Personal Genome Machine). With the proper preparation of the methodology the PGM allows obtaining comprehensive data on the genetic condition of the embryo. The patient is administered only the embryos free from abnormalities, therefore the couple gets the chance to have a healthy child.
In the future the specialised DNA sequencing tests will be performed in a woman and a man who are just preparing for enlarging their family. They will allow assessing the risk of occurrence of genetic diseases or defects in their future child. The physicians, having access to the detailed data on the genetic information of the potential parents, with the use of the special software will compare them and by reference to the mechanisms of inheritance will be able to determine the scale of the risk. Later on they will recommend the embryo testing, if appropriate.
Indications for the application of PGD NGS
The preimplantation genetic diagnosis with the next-generation DNA sequencing (NGS) is the solution intended in particular for:
- women deciding to become pregnant after they reached the age of 37,
- persons diagnosed as the carriers of genetic diseases,
- persons with genetic defects in the family (so-called positive genetic family history),
- women with recurrent spontaneous abortion,
- couples with the failure of the previous IVF programmes – despite administering the embryos with normal morphology,
- couples treated for idiopathic infertility for a long time
- persons concerned about having a baby with a genetic defect.
This new method provides unique opportunities as regards the range of obtained information as well as the sensitivity and precision of testing. The difference in the technology is as significant as the difference between the first cameras and the current digital technology. With the earlier microarray technique, obtaining the data of such quality was so far impossible. It is worth remembering that the key factor deciding on the success of PGD is the expertise of embryologists who collect the material for testing – due to the high sensitivity of embryos, the procedure requires enormous proficiency and the ability to select the optimum cell for analysis. This relates both to the FISH and microarray method (e.g. aCGH) and to the next-generation DNA sequencing. The INVICTA embryologists have been performing such diagnostics for over 9 years, with nearly 5 thousand tests completed in this period. This puts the Clinic in the 7th place in the world in terms of the number of completed cycles of PGD.
How does PGD NGS differ from other methods of embryo testing?
- This is the exceptionally sensitive method. The analysis covers more than a dozen thousand points on all 46 chromosomes. The previously used methods (microarrays, aCGH) allowed testing of only several dozen sites (which should be indicated precisely by the physician), thus giving much less information. Now the examination of one fragment of DNA can be conducted several hundred times, giving the extremely reliable and precise result.
- The next generation DNA sequencing (NGS) is described as the reference method (model for others), mainly due to the direct nature of the genetic material reading. Other methods (FISH and microarrays) use markers and light as change markers. Moreover, these techniques require the advanced optics which is prone to failure and not always provides the reliable results. For this reason, these methods are currently being abandoned for the use of NGS.
- PGD NGS, preimplantation genetic diagnosis with the use of the next generation DNA sequencing, allows testing for chromosome abnormalities (aneuploidies), monogenic diseases (including nearly 700 rare diseases) and translocations. It has not been possible until now.
- Given the short time of test performance (even less than 8 hours) the complete procedure can be conducted in embryos in the blastocyst stage in the so-called fresh cycle which increases the chances of pregnancy within in vitro fertilisation.
- It is possible to test the cryopreserved embryos. If a couple completed the in vitro programme and learned about their genetic burden following the programme completion, they may ask for performing the testing of the cells of embryos deposited in the bank; therefore the woman does not have to undergo the stimulation stage again and the whole process is much less expensive.
- There is a possibility to perform DNA testing of future parents even before the couple start trying to get pregnant. Both a woman and a man – despite their good health condition – can carry genetic mutations. The new method allows determining which of these abnormalities may have influence on the risk of occurrence of a defect in the child of a given couple. Based on this information, if the risk of fetal disease is significant, the couple may choose the in vitro fertilisation with preimplantation diagnosis and risk elimination. For some people this is the only chance of having healthy children.
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