Role of glycolysis in mesoderm specification and self-organisation of the anterior posterior axis in the mouse embryo.

One of the most important events in pregnancy occurs early in the process, when the embryo implants into the uterus of the mother. This event it so crucial for pregnancy success, that implantation failure is estimated to be responsible for around 30% of miscarriages. Repeated issues with this step during assisted reproductive therapy is considered as a condition called recurrent implantation failure and can be devasting for parents hoping to conceive through in vitro fertilisation (IVF). From the perspective of the embryo, implantation also reflects an important moment in its development. As embryos begin to develop and grow, cells must be come different from one another in a controlled manner so that the full spectrum of different cell types are generated. These different early cell populations must also grow and expand at the correct rate, so that organs are generated of the correct size and proportion. As developmental biologists, we know a lot about what controls the generation of different cell types, and as this is beginning around the stages of implantation, it is a major focus of many research laboratories across the globe. However, the question of how cells uptake the correct nutrients to expand these early cell populations is relatively understudied. In fact, we know very little of how these two essential processes: cell differentiation and growth, are coordinated in early development. It is essential to know more, as problems in the provision, uptake and usage of nutrients by the early embryo may be important for our better understanding of early pregnancy loss. In addition, it is likely to provide researchers in IVF clinics improved methods to assess the health of embryos in their selection for embryo transfer to the mother.
How cells uptake and use nutrients is a highly complicated process, that uses multiple overlapping metabolic pathways inside the cell. This research proposal will focus on understanding how cells specifically uptake glucose in a region of the early embryo called the mesoderm. This region later gives rise to many tissues in the adult body including the blood system, skeletal muscle and much of the skeleton. We will build on some preliminary data showing a surprising result that these cells have transporter proteins on the cell membrane to uptake glucose in a selective manner. We will follow how this glucose is used within the cell to fuel the generation of new cellular components important for regulating the growth of mesoderm progenitors. At the same time, we will look at how glucose is broken down and used in other parts of cellular metabolism linked to the regulation of developmental signalling pathways. We know these signalling pathways very well, as they are known to be important for the generation of multiple distinct cell types in early development, and in particular the early mesoderm. Therefore, we will uncover a direct link between the regulation of cell differentiation and growth. This will have far reaching consequences, both for an improved understanding of what happens in early pregnancy loss and for improving experimental protocols for the differentiation and expansion of specific cell types from stem cells and their use in regenerative medicine.

As organs and organisms develop and grow, two cellular processes must be tightly coordinated. In the first, cells must undergo a series of cell specification events to generate the complete array of required cell types. Secondly, progenitor populations must grow and proliferate at the correct rate to generate well-proportioned organs and tissues. Understanding the control mechanism that links growth and differentiation is both essential for a full appreciation of the underlying mechanisms of embryonic development and for the understanding how these cellular behaviours become uncoupled in the transition from homeostasis to cancer pathogenesis. This proposal aims to investigate the molecular mechanisms that lay at the interface between these two processes, as the early mesoderm is specified and expanded during early gastrulation. Given glucose is the most commonly used carbon source for energy production and biosynthetic pathways, we hypothesise that glucose uptake and metabolism is a central component in linking specification and growth during mammalian gastrulation. To test this, we will use and experimental system that enables the alteration of nutrient supply and metabolism in a controlled manner. During the course of development, a pole of mesodermal cells forms and break the symmetry setting up the anterior-posterior axis in gastruloids. We will first determine how glucose import is regulated by the differential expression glucose transporters. Next, we will determine the importance of glucose uptake in growth and specification of early mesoderm. Finally, we will implement state-of-the-art metabolic flux analysis to determine how glucose is metabolised through different biosynthetic pathways. Ultimately, this work will provide improve our ability to manipulate cell types metabolically to obtain specific cell types in vitro for further applications such as regenerative medicine.