Measuring and Mathematically Modeling Ionic Transport in Auditory Systems

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Throughout the animal kingdom, ears finely tuned for picking up vibrations in the air allow animals to sense the world around them at a distance. The sensory receptors that translate nanometer-sized movements into electrical events that underlie hearing, have quite different shapes and locations in the ears of vertebrates and invertebrates. Despite this, it is remarkable that all auditory receptors rely on differences in potassium concentrations between cellular compartments to power them, unlike other receptors that use sodium or calcium gradients. This project will use sensory cells in fly (Drosophila melanogaster) 'ears', which are located within its antennae, to understand the processes that lead to the development of such potassium gradients. Results from this research will generate molecular tools for measuring potassium concentrations inside and outside cells. In addition, the project will develop mathematical tools for illuminating the operation of complex cellular systems, and, as part of the broader impact objectives, it will also develop a set of experiments using equipment from Backyard Brains, which can be performed in high school biology classes and which will be designed to help students understand electrical current flow in living organisms, an idea which presents a challenge for many students. Summer workshops will give high school teachers the opportunity to use the equipment, which will then be made available for them to use in their classrooms. In addition, the project will expand the field of Computational Biology/Neuroscience at the University of Iowa by training undergraduate and graduate students.Central to this proposal is the use of scolopidia, the mechanoreceptors of Drosophila ears, as a tractable model for studying the processes that establish potassium gradients. Scolopidia are cellular ensembles, consisting of sensory neurons and supporting cells. One support cell is the scolopale cell, a glial-like cell that envelops the sensory dendrites, creating a space filled with receptor lymph, which has a high potassium concentration. The project will use the powerful genetic tools developed by the Drosophila community, to identify the nature and location of ion transporters involved in generating potassium gradients. The project proposes to develop novel genetically-encoded potassium indicators to determine the ion’s concentration in the scolopale space. In addition, mathematical models that capture the dynamics of the coupled scolopale cell and its extracellular space, and that shape the electrical properties of fly ears, will be built. There is much to learn about the coupling of electrodiffusion processes between cells, to clarify the understanding of several physiological processes in cellular ensembles like epithelia. Since scolopidia are also found in mosquito ears, the research could provide new insights to help combat this prominent disease vector.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.