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Jung-Bum Shin, Ph.D.
Assistant Professor
Department of Neuroscience
mailto:js2ee@virginia.edu
Ph.D., 2003, Free
University Berlin, Germany
2003-2009 Postdoctoral Fellow, Oregon Health Science University,
Oregon Hearing Research Center and Vollum Institute
Auditory Neurobiology
Hearing loss is America's leading disability, affecting millions of people of all ages. To develop preventative and restorative clinical approaches, it is crucial to understand how the hearing process works on the cellular and molecular level. Hearing is mediated by specialized hair cells in the inner ear, and the goal of our lab is to learn more about their function: how do hair cells develop, what proteins are they made of, and what are the molecular mechanisms of their dysfunction that cause hearing loss and balance defects? To this end, we use a variety of techniques to identify and characterize proteins involved in hair cell function.
Our lab combines Proteomics and Genomics to identify proteins and genes that are involved in hearing and deafness. Using this multi-faceted approach, we have already identified several genes that are involved in hearing loss (e.g. FSCN2), and we are currently working on several novel genes with possible roles in hearing and deafness.
Our lab is especially interested in the question of how the hair cell maintains its integrity over the years. Hair cells are among the cell types that cannot be renewed and therefore require a special maintenance strategy. Our hypothesis is that hair cells maintain their functionality by constantly turning over its proteins, and we use metabolic labeling in combination with peptide mass spectrometry to measure protein turnover in hair cells. We are especially interested in changes that occur during pathological stress situations (mechanical and oxidative stress).
Another focus of our lab is the dynamic behavior of hair cell proteins, especially components involved in the mechanotransduction process. We want to describe the subcellular movements of proteins that are involved in establishing and executing the mechanotransduction process, using in-vivo imaging. We will generate transgenic Xenopus frogs that express GFP-tagged proteins in hair cells and monitor the movement of these proteins in the living hair cell. We are especially interested in observing the dynamic processes associated with the disruption of the transduction complex caused by cellular stress situations, such as oxidative and mechanical stress.
Research projects
1.) Proteomics and genomics approaches to identify deafness genes
Proteomics and
Genomics technologies have contributed enormously to recent
advances in biomedical research. Our lab is using a
combination of Proteomics and Genomics tools to further our
understanding of the the components that are involved in the molecular
process of hearing. In short, we 1) sequence proteins in the
sensory hair cell using mass
spectrometry, 2) compare the proteomics data with
genetic data to identify possible
deafness genes and 3) generate transgenic mouse models
to evaluate the role of these putative deafness genes in vivo.
Techniques used: Mass spectrometry, DNA Sequencing,
Generation of transgenic mice
Model organism: Mouse
2.) Monitoring protein dynamics in hair cells using microscopy:
this project, we will study the immediate changes that are correlated with oxidative and mechanical stress to hair cells. Our goal is to visualize the dynamic processes that follow the disruption of the mechanotransduction complex. Of equal interest are the dynamic processes that enable the regeneration of the mechanotransduction complex, possibly involving the redistribution of mechanotransduction proteins. In order to observe the dynamics of bundle proteins (especially transduction complex components) in response to oxidative and mechanical stress, we will express tagged proteins in hair cells and monitor the movement of these proteins using in vivo fluorescence microscopy. Visualization of cellular and molecular events is a powerful tool, and the introduction of the Green fluorescent protein (GFP) and its variants has enabled us to visualize the action of proteins in their native cellular environment. Introducing and expressing genes of interest into hair cells has been difficult so far. Our approach is to generate transgenic Xenopus frogs that express a GFP-tagged version of our proteins, and to monitor these proteins in isolated frog hair cells.
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Inner ear organ of a transgenic Xenopus laevis frog expressing GFP in hair cells and supporting cell |
Techniques used: Xenopus transgenesis, confocal fluorescence
microscopy, DNA cloning techniques
Model organisms: Xenopus tropicalis, rat, mouse
3.) Turnover of hair cell proteins and its relevance for
auditory pathologies:
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Measuring protein turnover in the hair cell: Metabolic labeling followed by mass spectrometry analysis |
The exquisite mechanical sensitivity of sensory hair cells comes with the price tag of mechanical and oxidative vulnerability. To develop preventative and restorative clinical approaches, it is crucial to understand how the integrity of the sensory hair cell is maintained. The main restorative strategy for maintaining functionality of the hair cell is the dynamic turnover of proteins. The assumption would be that a healthy hair cell is able to counterbalance the accumulation of fatally modified proteins, whereas a defective hair cell or an excess of oxidative and mechanical stress leads to a breakdown of the turnover potential of the cell. Studying protein dynamics in the hair cell has proved to be difficult, due to the scarcity and fragile nature of hair cells and the lack of efficient gene delivery methods. We plan to measure the turnover of hair cell proteins by using metabolic labeling of hair cell proteins followed by mass spectrometry analysis.
Techniques used: Peptide mass spectrometry, explant organ
culture, metabolic labeling
Model organisms: Mouse, rat, Xenopus tropicalis, chicken
embryos
3.) Re-building the hair bundle:
| Blue: Novel bundle protein of unknown function |
In no other cell type is the principle "Form follows Function" as evident as in hair cells. Hair cells display a stunning cellular architecture that is optimized to execute its primary function as a mechanoreceptor. The goal of this project is to identify proteins that are responsible for certain features of the mechanosensory hair bundle, such as the tip and the basal taper of the stereocilium. We previously performed a mass spectrometry based screen to identify hair bundle proteins, and we will use this extensive list of bundle proteins to match the function of proteins with specific features of the hair bundle. Candidate proteins are involved in actin polymerization (important for tip and taper architecture) and protein-protein interactions.
Techniques used: Cell culture, transfection techniques,
DNA cloning techniques, protein biochemistry, immunofluorescence
labeling.
Model organisms: chicken embryos, mouse, rat
Selected Publications
