Neuronal and molecular basis for magnetic transduction in the nematode C. elegans

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This research will investigate how animals that use the earth's magnetic field for navigation and transform this force field into meaningful nervous signals and behavior. The magnetic field of the earth has horizontal and vertical components and while many animals are known to use either the horizontal (e.g. salmon), or the vertical component of the field (e.g. sea turtles), how they detect and translate this information is poorly understood. Determining how animals detect and process magnetic field information will solve one of the modern mysteries of sensory neuroscience. It will also improve our understanding of animal behavior by clarifying how living systems interact with natural and artificial magnetic fields. More specifically, this research will determine the subcellular location and nature of magnetic particles in the nematode C. elegans by identifying the molecules that allow worms to detect and orient to magnetic force fields. Further, it will elucidate how the nervous system processes magnetic information. The project will support the training of high school, undergraduate, and graduate students, as well as ongoing outreach efforts to increase science literacy among at risk children. Specifically, high school students will be trained through an ongoing summer science "boot camp" program and by recruiting local high school students to volunteer in the lab. They will learn how to generate hypotheses, perform experiments to test them, analyze and communicate their findings. Several graduate and undergraduate students will be given the opportunity to participate directly in the project, thereby gaining a complete scientific research experience. Graduate and undergraduate students enrolled in two biotechnology laboratory courses will also benefit by learning modern molecular techniques in the context of ongoing scientific research. All participating students will learn basic scientific literacy with the goal of presenting abstracts at meetings and co-authoring scientific publications based upon their research. The production of a behavior relies on the interaction between the sensory, integrating, and motor systems in an individual. While much is known about the transduction of most sensory modalities, how animals detect and orient to the earth's magnetic field remains one of the final frontiers of sensory neuroscience. Recently, the principal investigator identified neurons that process magnetic information, identifying candidate mechanisms for magnetic sensation, and, importantly, the first magnetosensitive neurons in any animal. This project will determine the cellular localization of magnetic particles in the tissues of C. elegans by purifying these particles in animals with fluorescently labelled candidate cells, or labelling them immunohistochemically. The size and composition of these particles will be determined using TEM and SEM-EDX analysis. Atomic force microscopy will be used to measure their magnetic moment and subcellular localization. To determine which proteins are responsible for assembling magnetic particles near the magnetosensory neurons, RNA interference will be used to silence iron-related gene expression. The magnetotactic response of these animals will then be evaluated, and the localization of magnetic particles evaluated through immunohistochemistry. Candidate proteins will be tagged using PCR-fusion. Previous mass spectrometry analysis of magnetic particles isolated from the tissues of C. elegans revealed them enriched for the mechanoreceptor PEZO-1 and several proteins involved in touch transduction in other animals. RNA interference will be used to silence candidate proteins involved in magnetic transduction and record the resulting changes in magnetic responses in the magnetosensory neurons using the calcium indicator GCaMP6. Sufficiency will be tested by means of cell-specific, ORF-mediated, rescue of candidate genes. Subcellular localization of these proteins will be accomplished through PCR-fusion to fluorescently tag them. To identify how C. elegans encodes magnetic fields, GCaMP6 will be expressed in sensory and downstream neurons. Neuronal responses will be recorded in animals exposed to magnetic fields of varying directions and amplitudes. Completion of this project will reveal how magnetic particles are assembled and contribute to the detection of magnetic fields by C. elegans. The resolution of the magnetic transduction machinery, and the neuronal basis of magnetic field coding will likely reveal conserved molecular and cellular strategies for harnessing the earth's magnetic field in the production of adaptive behavior.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.