Dynamics of Calcium Signaling in Multicellular Systems: Quantitative Experiments and Computational Modelling

Development of fully functional organs from undifferentiated cells requires constant communication between various participating cells. An important component in this cellular communication machinery are second messenger systems that relay external mechanical, chemical and hormonal stimuli to the genetic machinery of the cells. Due to their conserved nature in both healthy and diseased tissues, and their roles in mediating numerous critical cellular processes, there is a considerable interest to elucidate mechanisms of signal integration and transduction using a range of model systems. However, the shear complexity of protein-protein interactions along with non-intuitive feedforward/feedback loops makes it challenging to comprehensively understand second messenger regulation in multicellular systems. The work herein describes multiple studies that incorporate quantitative experiments using microfluidic- based cellular and organ-based assays, multiscale computational modelling along with transcriptomic approaches to reverse-engineer the dynamics of Ca²⁺ signaling during epithelial morphogenesis. Decoding the coupling between multicellular calcium dynamics and downstream gene regulation is critical in identifying new therapeutical approaches for addressing diseases exhibiting dysregulated calcium signaling and paves the way to define biological design principles important to rapidly advance the emerging field of synthetic biology. Towards this end, a review of the selective set of studies exploring the interplay between morphogen-directed positional informational systems and physiological signals including Ca²⁺ is presented in chapter 1. More specifically, the role of physiological signals in mediating and moderating morphogen-based response in multicellular systems is emphasized. In chapter 2, a quantitative image-analysis pipeline is presented to decode organ-level calcium signaling dynamics in Drosophila wing discs. Using this pipeline, we show that the calcium signaling dynamics is strongly correlated with physical properties of the organ such as the size. Based on these experimental findings, a multiscale mathematical model is formulated and presented in chapter 3 to explore the dynamic instabilities in Ca²⁺ signaling caused by the physical and chemical properties of the individual cells in the developing organ. In chapter 4, an experimental investigation using genetic tools along with omics analysis on the role of Gq mediated spatiotemporal Ca²⁺ waves in organ development is presented. Major findings from our studies along with future directions are presented in chapter 5.