In the Zernicka-Goetz lab, I will be working on a model of mosaic embryos to understand the fate of the aneuploid cells and how they interact with normal cells in vivo during early mammalian development. Aneuploidy refers to a major change in the number of chromosomes in a cell and is associated with pathologies such as cancer and Down syndrome. It is known that aneuploidy causes low human fertility and most developmental defects. The majority of pre-implantation embryos are mosaics of euploid (normal) and aneuploid (abnormal) cells, and some mosaic diploid-aneuploid human embryos are able to develop to term. In this context, how aneuploid cells contribute to developmental pathologies and how they are eliminated in human embryos are outstanding questions in reproductive and developmental biology. Mouse models for chromosome mosaicism enable analyses that are not allowed with human embryos for ethical reasons. Therefore, I will use a mouse model of chromosome mosaicism previously generated in the Zernicka-Goetz lab. Using this model and state-of-the-art techniques in developmental biology, molecular genetics, genomics and in vivo imaging, I will address: 1) how aneuploid and diploid cells interact and compete with each other, 2) which signaling pathways are activated during the elimination of aneuploid cells, and 3) how diploid cells are able to compensate for the elimination of aneuploid cells. Results from this work could contribute to the understanding of aneuploidy in mosaic human embryos in the IVF setting and give insights into how cancerous aneuploid cells are able to trick normal cells and proliferate to form tumors.