Title: Sensing and Information Transmission in Cell Biology

Abstract: One of the hallmarks of life is its ability to sense and respond to its environment, this enables cells to communicate with each other. Cell-cell communication permits spatiotemporal coordination which allows cells to perform tasks that they would not be able to do individually. This thesis examines the molecular communication between cells at two different scales. The first being the simplest possible case, just two cells. While the second involves hundreds of cells directly coupled together. The two cells in the first case are mating yeast cells. Yeast paradoxically degrade the signal from their partner that they need to detect. While the data processing inequality suggests that such signal modification cannot increase the sensory information, we show using a reaction-diffusion model and an exactly solvable discrete-state reduction that it can. Experimental data suggest that mating yeast operate in the beneficial regime where degradation improves sensing. The second case involves hundreds of neuronal cells coupled together via gap junctions in a confluent monolayer that are subject to periodic stimulation. We provide mathematical modeling to understand two separate experiments. In the first we show that increasing the coupling strength between the individual cells can decrease the synchronicity of the cells before ultimately increasing it. This is due to the added connectivity strength causing normally dormant cells responding, but with a delay. The second experiments shows that connecting cells together can decrease synchronization between them. Our model offers an explanation: coupling desynchronizes cells because their internal dynamics are near a bifurcation. This bifurcation is known to promote desynchronization among intrinsic oscillators, and here we show that it promotes desynchronization among periodically driven excitable responders.