Metabolic regulation during extraembryonic endoderm differentiation
Abstract
The inner cell mass undergoes orchestrated cellular divisions resulting in the formation of the epiblast (EPI) and primitive endoderm (PrE). Understanding the process of cell fate specification is crucial to appreciate the intricacies of proper embryonic development. While the mouse embryo is an excellent model, limitations do exist with number, technical challenges, and accessibility, therefore, in my thesis I employed two cell-based models to recapitulate the EPI-PrE fate in vitro. Many signaling pathways have been implicated in this lineage decision, metabolism and its downstream products have been recently regarded as a driver of lineage commitment. Using various biochemical, molecular, and computational modalities, I sought to understand how metabolism and ROS play a role in XEN differentiation. In Chapter 2, I demonstrated that ROS generated by NOX1 and NOX4, which are regulated by the GATA6 transcription factor, is required to induce XEN-like differentiation. While exogenous ROS supplementation promoted XEN-like differentiation, overexpressing Nox1 and/or Nox4 produced high levels of ROS yet failed to promote XEN-like differentiation. Next in Chapter 3, I examined if mitochondrial ROS played a role in XEN-like differentiation. Strikingly, the metabolic profile of XEN-like cells was glycolytic in nature. Furthermore, these observations were further supported using embryo-derived XEN cells (Chapter 4), which also relied on glycolysis as an energy source. Metabolomic and biochemical analyses showcased how embryo-derived XEN cells maintain high lactate levels by increased LDHA activity and re-routing pyruvate away from the mitochondria. More importantly, modulating pyruvate-lactate fate using pharmacological agents affected XEN differentiation in vitro. Collectively, my results emphasize how metabolism, and its products contribute to XEN differentiation, and more broadly serves to expand our knowledge of mammalian development.