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The auditory hair cells and spiral ganglion neurons in the inner ear serve as the backbone in the mammalian hearing process converting auditory waves into electrical impulse. The two types of sensory ganglion neurons, type I and type II innervate the inner hair cells and outer hair cells respectively. Despite a substantial amount of research directed toward understanding the development of these neurons the specificity of how these neurons innervate specific subtypes of hair cells remains unknown. In this study we analyze how the manipulation of inner and outer hair cells will impact neuronal projection. The specific hair cell subtypes are removed to analyze whether they guide the specific neuronal projection or if the neurons rely on another cellular source for their peripheral guidance. To alter the formation of specific subtypes of hair cells we utilized mouse strains that have disrupted the formation of specific subtypes of hair cells. Mouse strains that have a mutation in Atoh1, a bhlh transcription factor were used. Atoh1, is involved in the differentiation of both of the two types of hair cells in the inner ear. By manipulating Atoh1 expression with a conditional knockout mouse model with a genotype Atoh1-cre:Atoh1f/f we produced mice that lost all IHC’s. This enabled the observation of projection of type I and Type II spiral ganglion neurons in the absence of inner hair cells. The data obtained shows that in the absence of inner hair cells all the SGNs project to the OHC indicating that the inner hair cells serve as a guidance for the specific projection of Type I Sensory Ganglion Neurons.
Tolossa, Meskerem, "Distinguishing the Molecular and Cellular Cues for Neuronal Wiring in the Inner Ear" (2019). Honors Theses. 3185.