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The Levinson Emerging Scholars Program

Daniel Kashima - Neurobiology and Music

Daniel Kashima Daniel Kashima entered the University of Washington as a music major and one who enjoyed learning about Biology. Over his first two years as an undergraduate, he developed a heightened passion for learning more about the brain and thus applied and also was accepted into the Neurobiology program. The idea of conducting research in this area intrigued him and he feels fortunate to be accepted as an undergraduate researcher in the laboratory of Dr. Ed Rubel in his third year.

Dr. Rubel’s lab attracted Daniel as the research there focuses on auditory neuroscience. This effectively allows Daniel to bridge his two passions. His research uses techniques in molecular biology and physiology to uncover more information on the chicken sound localization circuit. Currently, he is using immunohistochemistry to look for an expression gradient of Eph receptors/ephrins along the midline of the chicken auditory system through development.

In his fifth year, the research component of his education continues to fascinate Daniel. He is currently trying to decide on what post-undergraduate path to pursue. Whether as an M.D., PhD, or both, research will undoubtedly be a major part of his future.

Daniel will graduate from the College Honors Program this Spring with degrees in Neurobiology and Music (classical guitar).

Mentor: Edwin Rubel, Otolaryngology-HNS

Project Title: The Role of Eph/ephrins in Axon Sorting in the Avian Sound Localization Circuit

Abstract: Auditory brain nuclei are organized in a tonotopic manner: the sound frequency to which neurons respond best, progressively and predictably shifts with its anatomical position, preserving the neighbor relationships of the auditory sensory epithelium, the cochlea. In birds, the bilateral nuclei n. magnocellularis (NM) and n. laminaris (NL). both part of a circuit responsible for sound localization, are arranged tonotopically. In each nucleus. neurons in the caudolateral region respond best to low frequencies (LF) and those in the rostromedial region respond best to high frequencies (HF). Our results show that axons projecting from NM to NL, thereby crossing the midline and forming the crossed dorsal cochlear tract (XDCT), are also arranged tonotopically. The mechanism governing this arrangement during development, however, is unknown. Studies done on the visual and olfactory systems implicate an expression gradient of Eph receptors and ephrins to form topographic axonal pathways. Although these molecules have been shown to be expressed in the chick auditory brainstem, no effort has been made to look for a gradient in expression in the XDCT. In order to address this, we will build on our results and look for a molecular gradient in XDCT. We will prepare parasagittal slices of chicken brainstem containing XDCT of 4 different developmental stages and use immunohistochemical methods to look for gradients in EphB2, EphB5, and ephrin-Bl expression. The slices will be imaged using widefield and confocal microscopy. Parasagittal sectioning incorporates the entire tonotopic extent of the XDCT into single slices such that protein expression levels will be compared within single slices. The presence of a gradient in Eph/ephrin expression will provide further insight into a possible mechanism underlying the tonotopic arrangement of the XDCT during development and can serve as a model to study the influence of molecular markers on axon sorting.