(261) Triploidy Triumph: Development of a Mouse Model of Aneuploidy

Around half of human embryos created by in vitro fertilization (IVF) globally have an abnormal number of chromosomes, a condition known as aneuploidy. While preimplantation genetic testing for aneuploidy (PGT-A) can detect this, it is invasive, costly, and time-consuming. Consequently, there is demand for novel non-invasive methods for aneuploidy detection. For such methods to be developed, robust animal and laboratory models of aneuploidy are essential. The aim of this study was to develop methods for creating embryos with three sets of chromosomes (triploid embryos) in mice. We hypothesize that the expression of key developmental genes between triploid embryos and control embryos will be different. 
Digynic embryos, with two maternal and one paternal sets of chromosomes, were developed by exposing mouse oocytes to cytochalasin-B at different doses and exposure times, preventing the expulsion of the second polar body. Diandric embryos, with one maternal and two paternal sets of chromosomes, were created by injecting two sperm into a single oocyte using intracytoplasmic sperm injection (ICSI). Total RNA was isolated from all resultant embryos and associated spent culture media using a phenol/guanidine-based lysis, followed by silica-membrane-based purification of total RNA. Total RNA was synthesized into complementary DNA for TaqMan qPCR experiments or used to generate libraries for next generation sequencing. The morphokinetic timings of developing embryos were also recorded using PrimoVision cameras. 
Exposure of embryos to 10 µg/mL of cytochalasin-B for 4 hours, beginning 3 hours post-insemination, successfully resulted in digynic triploid embryos. A proportion of these embryos (11.1%) developed through to the blastocyst stage. In contrast, both euploid and diandric triploid embryos generated via ICSI at 16 hours post-hCG administration exhibited limited development and failed to progress beyond the two-cell stage. Significant differences in the expression of key developmental genes were observed between embryos of differing ploidy status. Additionally, embryos which took longer to reach certain morphokinetic milestones were less likely to develop to the blastocyst stage, but timings were similar between ploidy states. 
By successfully generating triploid embryos, we have established a model for studying aneuploidy during early embryonic development. The aneuploidy model did display differences in expression of key development genes, despite no differences in key cleavage timings, compared to euploid embryos.