Characterization of aneuploidy, cell fate and mosaicism in early development

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PROJECT SUMMARY The presence of aneuploidy (chromosomal abnormalities) in embryos is considered one of the major limitations to successful human reproduction and a significant cause of gestation failure, accounting for approximately 50% of early miscarriages. Aneuploidy rates are strikingly high in in vitro fertilized human embryos, and around 60% of these embryos are mosaic, containing both aneuploid and normal euploid cells. The frequent occurrence of mosaicism exists in both naturally conceived and IVF pregnancies. However, despite the high incidence of aneuploidy in human embryos, our knowledge of the molecular mechanisms and developmental fate of these cells is restricted due to the considerable ethical limitations associated with human embryo and fetal research. My previous work demonstrated lineage-specific behavior of aneuploidy in early differentiation using an in vitro human embryonic stem cell (hESC) model. To further characterize the cellular physiology of aneuploidy after implantation, an in vivo animal model is required. Common marmosets exhibit naturally occurring aneuploidy, making them a more representative model for humans than rodents are. Therefore, I propose a marmoset model to further dissect aneuploidy cell fate and its molecular and cellular consequences during early development. My preliminary data uncovered that aneuploid marmoset embryonic stem cells (cj-ESCs) preferentially differentiate into trophectoderm lineages in response to BMP4 stimulation, similar to the behavior I observed with hESCs in my previous work, suggesting a conserved role of aneuploidy in restricting stem cells to extraembryonic fates. During the training period, I will use a unique marmoset stem cell model (gastruloid) that recapitulates early lineage specification and gastrulation to investigate the role of BMP4 signaling in the phenotypic manifestation of aneuploidy (Aim 1). To further investigate the elimination and allocation of aneuploidy, I will construct mosaic marmoset embryos to probe aneuploidy cell fate and behaviors during pre-and post-implantation embryonic development in vitro (Aim 2). Since my preliminary data indicates a higher tolerance of aneuploidy in the extraembryonic lineages, during the independent phase of the award period, I propose to analyze the gene expression profile of aneuploidy in the marmoset placenta to understand the effects of aneuploidy on the cellular physiology of extraembryonic tissue. In addition, during this phase, I will construct a placental/trophoblast organoid from cj-ESCs to further dissect the behaviors of aneuploidy in different placental lineages (Aim 3). Together, the proposed research will present a comprehensive model for studying a previously uncharacterized mechanism underlying the elimination of aneuploidy during embryogenesis, paving the way for translational applications to assisted reproductive technologies. The proposed project will also serve as a platform for me to obtain training and scientific expertise in molecular and developmental biology, animal reproductive sciences, and computational genomics which will contribute significantly to my career development as an independent investigator in the field of reproductive biology.