Developing new tools and technologies to study calcium signalling in the brain's immune system

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Calcium (Ca2+) is a universal and diverse second messenger critical for general and specific cellular function, with its intracellular (IC) concentration finely maintained by a cell-specific toolkit of pumps, channels, and buffers. The cell and context specific expression pattern of these enables spatially and temporally heterogeneous changes in intracellular Ca2+ concentration, exploited for diverse phenotypic outputs.In neuroscience, Ca2+ signalling is vital for information processing via action potential propagation and neurotransmission in electrically excitable neuronal cells, coupled to changes in voltage. However, intracellular Ca2+ changes are also associated with activation of non-excitable cells of the central nervous system (CNS), particularly microglia, CNS resident surveillant innate immune cells activation of which occurs during neuroinflammation. Neuroinflammation is broadly defined as the set of CNS-localised and coordinated immunovascular responses to cell damage, and is associated with distinct changes in microglial morphology alongside a spectrum of "pro-inflammatory" phenotypes such as secretion of cytokines and chemokines, phagocytosis, and inflammasome activation. Although increases in calcium signalling in microglia with a range of characterised inflammatory stimuli have been measured in vitro and in vivo, and correlation with other microglial and neuronal phenotypes identified, stimuli specific thresholds and mechanistic details including the precise calcium mobilisation mechanisms and downstream phenotypically relevant signalling events involved remain ill-defined.Broadly, this PhD project aims to develop to generate a new understanding of how IC calcium signalling links to microglial activation states via generating microglial 'fingerprints' using high content imagine (HCI) approaches. These fingerprints will multiplex reports of intracellular calcium signalling with other physical, chemical, and functional readouts without assumption of which properties will correlate. A suite of novel in vitro assays in human microglia (HMC3) and neuronal (SH-SY5Y) immortalised cell lines will be developed and optimised in parallel. Initially, assays will benchmark of a broad spectrum of characterised "pro" and "anti" inflammatory stimuli associated with microglial activation covering a broad range of microglial expressed receptors, as well as treatment with novel tool compounds synthesised in house by chemists in the Madden lab. Some of the most amenable and powerful phenotypic assays will be upscaled for screening pre-annotated compound libraries using HCI (automated microscopy imaging of multiple endpoints (Lilly, 2018)) with the aim of identifying novel neuroinflammatory modulators and targets without prior knowledge of the molecular pathways involved. Image acquisition will likely use the CellDiscover for end-point and the IncuCyte for kinetic assays. Identified hits will then be taken forward for downstream target deconvolution, potentially discovering novel targets for treatment of neuroinflammatory associated diseases. Dysregulation of neuroinflammation is implicated in aetiology and/or pathogenesis of a range of brain disorders including dementias, neuropsychiatric conditions, and traumatic brain injury complications.