Couples carrying known and matching genetic mutations, who can fall pregnant naturally, will need to seek IVF treatment in order to guarantee they are carrying a healthy embryo onto pregnancy, also known as “Single Gene Disorders” which are diseases created at gene level and is influenced on a specific geographical area in the world or ethnic group. The gene mutations for example, could be cystic fibrosis which is found in the population from Europe, Thalasemia, which is found in the populaion in the Mediterrenean area, sickle cell disease which is found in the population in Africa, Fragile X syndrome found in South America, muscular dystrophy found predominantly in the male population, or Huntington disease found in the European population.
Before seeking IVF treatment, couples need to undergo specific detailed genetic testing to determine the mutation they are carrying and then a special personalised testing method is created to check for the specific matching gene in the embryos. Once the results are obtained from preparation for the genetic testing it is then advised that couples can then begin IVF stimulation process to produce eggs, which is then injected with their partner`s sperm and left to fertilise. Day 3 of fertilisation shows the development of the embryos as a cluster of 4-8 cells. At this point in order to check the health of the embryos, a biopsy is performed where one to two cells are removed from the embryo very carefully and then sent for genetic testing.
Embryos obtained through IVF can be screened for the matching mutation gene that both parents are carriers of and can show which embryo is healthy and not a carrier of the gene, embryos that are only carry one of the mutation genes which shows they are only carriers or which embryos are exposed to both of the mutation genes and will go on to develop the genetic illness. This means that embryos carry a 50% chance of inheriting the disease from the mother and father. Embryos that undergo genetic testing can then be identified and determine and the disease carrying embryos are not transferred and separated from those identified as healthy embryos, and families are given the opportunity to have a healthy baby by the transfer of healthy embryos.
Couples, who are carriers of matching gene mutations, who fall pregnant naturally, carry a 50% risk that their child will be born with the disease, this can then lead to psychological problems and serious trauma as couples are then faced with the decision of whether to terminate the pregnancy as the disease can only be detected after 11 weeks via amniocentesis which also carries a risk to the child.
If couples carry the pregnancy to full term with their child being exposed to the disease then IVF technology can be used in order to bring an immunological “HLA compatible” baby for the affected sibling, who would need stem cell transplantation from a genetically “healthy” and suitable donor, to the world. This method is called “HLA typing in embryo” and it is performed in worldwide prestigious centres with high standards that our health group is also within.
PGD applications need a well-managed team, working together in which not only clinicians and embryologists are present but also genetics specialists and scientists working in the field of molecular genetics.
PGD in Rare Genetic Disease Carriage – Steps of the Treatment:
A standard PGD application for rare genetic diseases consists of six basic steps:
Genetic counselling and the evaluation of the status of the existing genetic disease carriage in the family:
The said genetic status should be examined in detail with couples first identifying the genetic pathology of the embryos and apply this technology. Hundreds of genetic diseases with a known mutation can be analysed in embryos with routine applications. However, there are also a wide variety of genetic diseases that does not show inheritance from family and can be found in one gene such as the Mendelian law which therefore cannot be analysed with modern technology in accuracy. Genetic evaluation and discussion of the said genetic status between the couple and with the experts are very important.
Preparation for the analysis at single cell level:
If genetic status or disease is clinically diagnosed, the pathogenic mutation or gene disorder should be identified and documented in all the people in the family by using advanced molecular genetic techniques. Then, an inheritance pattern and form of mutations are detected and analysed accurately according to the results. Many other genetic regions are also analysed additionally in order to minimize the disorder rate, because the diagnosis is at single cell level and this is included into the preparation process. This preparation phase is the most important and time-consuming part of the whole treatment package and the conclusion may take several days or several weeks depending on the complexity of the disease in genetic terms.
Ovulation induction and IVF treatment:
When preparation phase is completed, genetic laboratory informs IVF clinic that routine treatment can begin. The physician calls the mother candidate for large-scale clinical evaluation and start ovulation induction protocol in order to produce a large number of egg cells if the results are appropriate. Collection, fertilization and embryo development process of the egg cells are the same as conventional IVF treatment.
To take cell sample from each embryo, whose development continued as expected, is required in order to determine the genetic structure of the embryos via embryo biopsy method. The main purpose of embryo biopsy is the removal of one or more cells without damaging the growth and development process of the embryo in normal conditions. It should be stated that this procedure carries a damaging risk during the procedure, since it is an invasive procedure. Nevertheless, this risk is much lower than similar risks in the amniocentesis procedure when performed by experienced personnel.
Detection of genetic diseases in biopsied cells:
According to the preparation protocol, the materials obtained after the biopsy are examined for the disease in question and whether the embryos, which the cells are obtained, are appropriate for transfer or not is determined. Embryos that are found to be “suitable for pregnancy” according to the results of embryo development and the results of genetic analysis are selected for embryo transfer. In some cases, embryo transfer stage can be delayed due to certain medical or social reasons. In these cases, the embryos appropriate for pregnancy are frozen via cryopreservation methods and can be stored until the embryo transfer (for months or years).
Embryo transfer with genetically normal/appropriate embryos:
Embryos that are determined to be genetically “healthy” are transferred to a suitable uterus environment via fresh or frozen embryo transfer methods.
PGD application in rare genetic disease carriage is a treatment method that we institutionally have been carrying out for many years and, it can be applied to all known genetic diseases/mutations that can been identified to cause the disease.