Aneuploidy
Cells with an abnormal number of chromosomes, called aneuploidy, are often observed in pre-implantation human embryos during IVF (in vitro fertilization). Such aneuploidies are thought to be the major limiting factor of successful human reproduction, causing only ~30% of all conceptions to result in a live birth. As such, preimplantation genetic testing for aneuploidy (PGT-A) has become an IVF add-on procedure to determine whether IVF embryos are to be considered for transfer or disposed of.
Aneuploidies in human embryos result from cell division errors pre- or post-conception. Division errors at the preconception stage result in embryos in which all cells have an abnormal number of chromosomes. Some affected chromosomes result in genetic syndromes, such as Down, but others lead to early developmental arrest. On the other hand, cell division errors in the post-conception stage lead to an embryo with a mixture of cells with a normal number of chromosomes and cells with an abnormal number of chromosomes, called mosaic embryos. Little is known about the developmental potential of these mosaic embryos.
Developmental potential
Nearly all human embryos show (some level of) mosaicism, and babies born of mosaic embryo transfers appear to be healthy, with mosaicism being resolved during pregnancy. Also, male and female embryos differently tolerate chromosomal abnormalities. As mosaicism does not necessarily result in an adverse pregnancy outcome, clinicians face the dilemma of whether to transfer mosaic embryos. This is very important for IVF couples, as one in five IVF couples has only mosaic aneuploid embryos available.
To better understand how different aneuploidies affect the developmental potential of the human preimplantation embryo, researchers from the Marks group will investigate the effects of aneuploidies during the early stages of embryonal development. Together with dr. Coonen, dr. Giselbrecht, and dr. Vrij from Maastricht University, they will use an early embryo-like model. Because the sexes tolerate chromosomal abnormalities differently, both male and female models will be studied. This research aims to provide a better guide for clinicians which embryo to choose for implantation to maximize chances of a successful pregnancy.
