Christine de Die-Smulders



In the column 'A conversation with...', experts from Maastricht UMC+ discuss one of the questions submitted for the National Research Agenda. This time prof. Christine de Die-Smulders, a clinical geneticist and Professor of Preimplantation Genetic Diagnosis, discusses the question:

How will knowledge of genetics play a role in the understanding of, screening for and treatment of (rare) diseases?

"This is an extremely complex question, so we will start by narrowing the focus of the question to a specific discipline within genetics, namely preimplantation genetic diagnosis (PGD), which involves the testing of the genetic material of an unborn child for specific serious hereditary diseases. The current situation in the Netherlands is that PGD can be used for couples who want a child and have an increased risk of a particular hereditary disease. Hereditary breast cancer, Huntington's disease and cystic fibrosis are some of the disorders for which we can test. This is how the procedure works.


Let's say that the prospective parents know that there is a strong hereditary predisposition for breast cancer. In that case, they are first examined themselves for the genetic defect. Using IVF (in vitro fertilisation), a number of eggs are taken from the woman and fertilised in the laboratory, producing a number of embryos after a few days. On average, such an embryo consists of eight cells. One or two of these cells are examined in the lab. Some of the embryos will have the genetic defect that creates an increased risk of breast cancer, others will not. The 'healthy' embryos can be reinserted into the woman's womb. Ultimately, there is a twenty-percent chance that the embryo will grow into a healthy baby. If the procedure does not lead to a pregnancy, it can be repeated up to three times.

There are four centres in the Netherlands that are able and permitted to perform the IVF treatment required for the PGD examination. In addition to Maastricht UMC+, they are the University Medical Centers in Groningen and Utrecht and the Academic Medical Center in Amsterdam. However, the hospital in Maastricht is currently the only centre that is allowed to perform a PGD and the embryo selection, while the other three centres can send the genetic material to Maastricht for testing and selection. PGD procedures have been performed for around twenty years now and the range of hereditary diseases for which we can conduct tests is growing.


However, we only ever screen for one disease (or at most two diseases) for which it is known that the parents might have an hereditary predisposition. In other words, the search of the genome is very precise. It is absolutely not the case that we can tamper to our heart's content with an embryo's DNA, which is a fear that is sometimes expressed. People wonder, for example, whether we will have 'designer babies' in future, with parents being able to choose the colour of their baby's hair and eyes. But that is totally out of the question. Quite apart from the ethical objections, it is not even technically possible.

What the future might bring is still a mystery, since there are many technological advances occurring in the field of genetics about which we need to ask ourselves whether we should use them. Take a recent example from the UMC in Groningen, where research is currently being conducted into a test that would allow prospective parents to be assessed for the risk that their child will have one of fifty different serious hereditary diseases. But what do you do with the knowledge that your child has a 25-percent chance of a serious condition? And what if the chance is ten percent, or fifty percent? Suppose we adapt the test so that it can screen for two hundred different diseases: what do you then do with the information? That is a lot of information for the prospective parents to process and it raises some difficult dilemmas: terminate the pregnancy or not? For that reason alone, with PGD parents can also request psycho-social support so that they can make their own carefully-considered decision.


So far we have only been talking about screening, but a recent development has also brought us a lot closer to genetic treatment. With the CRISPR-Cas9 technique it is possible to simply cut out a genetic defect at a specific location in the DNA. With this method, the unwanted genetic material in a damaged embryo could be easily repaired. In that case, you would also no longer have to dispose of 'defective' embryos. Although that is still a pipe dream, we do already need to start asking ourselves how we should deal with such techniques. In other words, there are already vast technical possibilities. The knowledge of genetics can certainly help us in understanding, screening for and even treating diseases. But the important question we have to keep asking ourselves is: how far should we go?"

Would you like to know more about PGD and clinical genetics?

PGD Nederland is a partnership between the PGD Centre at Maastricht UMC+ and the PGD transport centres at UMC Utrecht, UMC Groningen and AMC Amsterdam.

The department of clinical genetics in Maastricht is part of the LAB Maastricht UMC+. The department is engaged in diagnosing and providing information about hereditary and congenital defects and is regarded as a centre of expertise in the field of medical genome diagnostics.

The CRISPR-Cas9 technique was voted the best scientific breakthrough in 2015 by Science, one of the world's most prestigious scientific journals.

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