Next generation approaches to understand tissue specific regulation of the glucocorticoid response

点击翻译按钮获取中文摘要

Understanding how the regulators of steroid hormone receptors work together to process the cells' response to glucocorticoids is fundamental to several fields of biology, including gene regulation, signaling responses and biological heterogeneity. These systems are highly relevant as not only are glucocorticoids naturally produced by the body, they are also some of the most commonly prescribed therapeutics worldwide because of their low-cost and anti-inflammatory effects. Therefore, throughout our lives, cells are constantly coming into contact with steroids, either produced by the body or therapeutically. The Glucocorticoid Receptor (GR) is a protein found in almost every cell in the body. The GR responds to the body's production of the steroid hormone cortisol and translates this signal into action by activating genes that control a diverse range of cellular responses, including development, metabolism and immune response. The GR has been extensively studied at the molecular level. Such research has revealed how cortisol activates the GR and leads it to enter the nucleus. Once in the nucleus the GR binds directly to the promoters and enhancers of genes, activating them. We have also learnt that the GR does not work alone: the receptor is regulated by a complex network of interactions including co-activators, co-repressors and epigenetic modifiers, along with other nuclear receptors. The range of responses caused by the presence of different regulators within the different cell types can be huge. For example, while GR activation promotes the growth of mammary tissue, the same activation of the GR causes lymphocytes within the blood to rapidly reduce in number. In order to precisely control the cellular response to steroids it is vital that we understand how the differences in these responses are controlled by these regulators. Once understood we will be able to reprogram one cell type to respond more like another. Given the ubiquitous nature of GR activating compounds this has far-reaching implications: enabling us to block an unwanted cellular response, activating novel responses in cells to selectively direct them to survive or die, or precisely target a specific tissue to gain a specific outcome. It is this knowledge gap that the present project will address. Typically, studies that focus on complex systems like the GR are extremely time consuming as each part of the system must be identified and studied in turn. Instead, we will apply leverage to the development of single cell experimental techniques to enable the study of the GR as part of a much larger system. The first step will be to detect the co-regulators that interact with the GR in response to glucocorticoids in multiple tissues. These will define the parts of the system that the GR interacts with and how they change between the tissue.The second step will be to delete the genes that encode for these parts, the regulators of the GR, and then monitor how it alters the cells' response to activating the GR. State-of-the-art single cell sequencing technology makes this possible by enabling us to increase the number of regulator genes we can target and increases the amount of data we can collect. Additionally, because single-cell sequencing requires fewer cells than previous methods, the technology enables us to undertake the work in cells from healthy volunteers.The data we generate that describes the GR responses in these gene-edited cells will be fitted, using current and future computational methods, to build a functional and experimentally testable representation of the network of co-regulators that modulate GR signaling in each tissue. This will effectually provide us with a wiring diagram of the different tissues.Finally, we will use the models we have generated to establish how to precisely alter the cells' response to steroids in each tissue.