Developing novel reporter systems to elucidate upstream regulators of cellular oxidative responses

Generation of reactive oxygen species (ROS) by the phagocyte NADPH oxidase is a critical and highly conserved antimicrobial function of myeloid immune cells such as neutrophils and monocytes. ROS production must be tightly regulated to ensure constant readiness for immune defence, while restraining inappropriate activation. A lack of ROS from this complex results in the devastating inborn error of immunity chronic granulomatous disease (CGD), characterised by recurrent infection but also autoinflammation and autoimmunity. Common hypomorphic variation in the genes encoding components of the phagocyte NADPH oxidase also drives pre-disposition to common autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Excess ROS production can, however, result in oxidative stress. Understanding how ROS is tightly regulated is thus important for the development of rational therapeutics immune-mediated diseases. 

Despite the elucidation of the NADPH oxidase complex structure and function, upstream regulators of ROS production remain largely undiscovered due to a lack of robust biological model systems. The Thomas Lab characterised EROS (Essential for Reactive Oxygen Species) as an indispensable regulator of ROS generation but we believe that there are many more. Recent developments in CRISPR-Cas9 technology now allows both the introduction of precise edits (homology-directed repair, HDR) and genome-wide forward genetic screening by introducing knockout (CRISPRko) libraries. This may identify therapeutic targets in inflammatory disease.

We will use CRISPR-HDR methods to endogenously tag key components of the NADPH oxidase complex with fluorescent proteins to generate reporter lines for iterative selection by flow cytometry. By screening these at genome-wide scale with CRISPRko libraries and sorting cells based on component expression, followed by functional screens using fluorescent ROS probes, we will elucidate upstream regulators of the complex expression and function. The function of these novel regulators can then be investigated and validated using primary and immortalised cells, structural biology, and selective mutagenesis. Interrogation of publicly available genomic datasets will guide ‘hit’ selection and possible therapeutic relevance.