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What is PGT and How to Save White Rhinos?

At the end of last year our embryologist Tuuli Dmitrijeva participated in a conference “Preconception, Preimplantation and Prenatal Genetic Diagnosis (PGT)” and finally we have managed to summarize some of her thoughts.

The conference presented a lot of topics for discussion including Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS), woman’s age as a factor regarding aneuploidy, advances in prenatal molecular diagnostics etc. What turned out to be the most interesting for You?

Tuuli: Indisputably all the brightest minds in the field were present. It felt like I was lost among the game changers in the field of prenatal diagnostics.

There were indisputable peaks in their field around the world. I felt like I had lost my way to the meeting of the evangelists of prenatal genetics in the world. With their presentations, scientists have contributed to the creation and development of today’s IVF world; I saw in real life people whose scientific articles I am studying from which I am learning and gathering wisdom.

Biggest point of interest was how it has been possible to create germ cells out of somatic cells. The method has been used to create a blastocyst, but no transplantation has been carried out on humans. This has however been tested on Northern White Rhinos with the aim of possibly recuing them from extinction. (https://www.bbc.com/news/science-environment-46109393)

Were there any topics or reports about which the opinions of the scientists are going apart, and thus was any of the topics really controversial?

Tuuli: A stormy reaction among doctors and clinical embryologists was caused by Dr Nathan Treff’s reflection on mosaicism, namely he claimed that much of the mosaicism results could be the artefacts of today’s technique and method. But the mosaicism, or the variation within the genetic material in body’s cells, in nature has been confirmed by e.g three-coloured cats or two different eye colours in a single person. It should also be mentioned here that this researcher is looking for opportunities himself and will soon be coming up with a new method / opportunity to conduct genetic research on embryos without invasive intervention (i.e without biopsy). His comment is probably a bit biased, but in 5 years’ time we will know better where the world is moving.

One of the most important questions of the congress was: Are we ready to change the human genotype for clinical purposes? What was the found common ground at the conference?

Tuuli: No answer to this question. Positive and negative aspects were discussed, but above all the general opinion reflects that we are not ready yet. Both technically and psychologically. The reaction of the world to the recent statement by Chinese scientist, He Jiankui, that he carried out a procedure where they started with genetically modified embryos and a baby from such an embryo was born, is a testimony to the fact that we still need to clarify and specify the ethical side of such experiments. By the end of the day, however, clinical embryologists know that there are things where they can take part and help, but the last word will always remain for the nature itself.

In addition, at this day and age we are faced with the fact that we have a lot of genetic information, perhaps even too much. Yet we don’t know how to use all that data. Technological advances have been so rapid, that we now have to catch up with the knowledge.

Returning to pre-transplant genetic diagnostics – is PGS / PGD analyses or so called “selection of a healthy baby” common in Estonia or are these studies a new thing for us?

Tuuli: PGS / PGD or PGT (preimplantation genetic testing), as its new name, is fully available in Estonia, but currently not listed in the health services covered by Estonian Health Insurance Fund. It has been available in our clinic for almost 2 years.

The goal of PGT is either to look for a specific genetic failure (a parent wishing to conceive has a genetic mutation and its transmission may contain pathological changes in the child’s phenotype) or look at the entire set of chromosomes of the embryo and to see if any signs of aneuploidy (is one missing or above one chromosome copy) ) or if any chromosomal relocations are present.

Although a few years ago it was stated that woman’s age and the aneuploidity of the embryos correlate, it has gathered some critique and is not stated so easily today. Why? Because aneuploidy has been observed as much in younger women as in older. Although this doesn’t mean that a woman’s age does not play any role. Alongside age, other factors will play a larger role with increasing age and this combination plays a role in getting pregnant and carrying the baby to a successful birth.

We thank Tuuli for an interesting interview and wish the best to our readers!

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