Molecular Mechanisms of Tonotopy Development in the Brain Stem

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ABSRACT Normal nervous system maturation is dependent on neurotrophin signaling. Neurotrophins are proteins, and along with their signaling receptor pathways, help regulate the development, maintenance and function of vertebrate nervous systems, making it a dynamic factor that promotes biologically relevant tasks. Irregular neurotrophin signaling results in pathophysiological conditions throughout the peripheral and central nervous system. In the auditory periphery for example, this includes atypical arrangement of innervation patterns along the frequency gradient (i.e., tonotopic axis) of the inner ear and hearing loss. Beyond the auditory periphery of all vertebrates, however, the establishment of functional specialization in the central auditory pathway via neurotrophin signaling are lacking. Understanding gradients of neurotrophin signaling is a significant and timely problem in developmental neurobiology in general, and the avian auditory pathway proves to be a particularly advantageous model system for experimentally examining it. A better understanding of normal auditory circuit assembly – along with the unique functional properties of brainstem neurons – will provide a significant foundation for developing stem cell-based therapies for auditory-related disorders. Stem cell-derived auditory neurons will only prove useful, therapeutically, if they are able to re-create specialized functional properties that are characteristic of normal auditory circuit maturation. A careful characterization of neurotrophin signaling, the underlying molecular mechanism by which they operate, the role it plays in establishing normal auditory properties and the functional consequence of altering this biological process is necessary and appropriate. The research proposed here aims at addressing these issues by providing a comprehensive understanding of developmental properties associated with neurotrophin signaling and its role in establishing normal functional phenotypes along the tonotopic axis in the cochlear nucleus: a brainstem structure essential for the temporal processing of sound.