Dissecting the role of Notch signaling in mouse pre-implantation embryo development

PROJECT SUMMARY/ABSTRACT During pre-implantation mammalian development, cells must make their first critical fate choice to specify the trophectoderm (which forms the extra-embryonic placenta) or inner cell mass (which develops into the embryo proper). To achieve this lineage commitment, the embryo coordinates the major mechanical changes of compaction and polarization with critical signaling programs that drive cell fate. The role of Yap mechanotransduction in guiding trophectoderm fate beginning at the 8-cell stage has been well-studied. However, trophectoderm development is not driven by Yap signaling alone, but also requires activation of the Notch pathway. While other developmental contexts provide insight into how Notch could interact with mechanics and Yap to guide cell fate decisions, the role of Notch in mouse pre-implantation lineage determination remains unknown. This proposal will elucidate how Notch integrates with Yap and mechanics to guide trophectoderm specification and pre-implantation embryogenesis. I will investigate the central hypothesis that Notch lateral inhibition starting at the 2-cell stage primes a subset of cells toward the trophectoderm lineage; during polarization, Notch signaling could stabilize the apical domain to reinforce Yap signaling and maintain trophectoderm identity through blastocyst morphogenesis. Historically, live cell dynamics of pre-implantation embryo development have been challenging to study due to phototoxicity. However, recent advancements in light-sheet microscopy, biosensors, and optogenetics allow us to visualize and perturb signaling dynamics with unprecedented spatiotemporal resolution. I will harness this high-resolution imaging system to determine (1) how Notch signaling relates to embryo mechanics and (2) how Notch and Yap signaling dynamics specify and maintain trophectoderm fate. For the completion of these aims, I will gain training in advanced microscopy, quantitative developmental biology, scientific communication, teaching, and mentorship. The expertise from my sponsor, Dr. Orion Weiner, an expert in signaling dynamics and cellular mechanics, and support from the F31 NRSA will ensure that I receive the mentorship and resources necessary to complete my proposed research and training plan. My work will reveal how the embryo integrates different modes of signaling with mechanics to guide cell fate decisions. A better understanding how pre-implantation development is regulated will help advance Assisted Reproductive Technologies and ameliorate infertility.