The search for the origin of chromosomal abnormalities in human preimplantation embryos

It has been known since the 1990ies that human preimplantation embryos obtained after in vitro fertilization (IVF) and intracytoplasmic sperm injection display an astonishing frequency -by and large ¾ of the embryos analyzed - of chromosomal abnormalities. These abnormalities can be inherited from the oocyte or the sperm, but more frequently they occur after fertilization, during the first
cleavages of the embryo. We want to study the origin of these chromosomal abnormalities through the analysis of the genome and the gene expression patterns in early embryos, between the zygote and the 8-cell stage. We will focus on the systems that the cell uses to check mistakes in segregation of chromosomes, however the analysis of all the genes expressed at such early stages, in combination with chromosomal abnormalities, may yield other markers of genetic health in the early embryo, which may improve IVF efficiency. Moreover, the embryo seems to have ways of dealing with these abnormalities, as at day 5, there seem to be much less abnormalities. This has been coined "self-correction" of the embryo. Thus, we want to determine the role played by programmed cell death (apoptosis) during the elimination of abnormal cells in blastocysts.