Research in our laboratory focuses on the cellular and molecular processes underlying differentiation of the mechanosensory hair cells of the inner ear, and on the innervation of these cells by axons of the eighth cranial nerve. The aquatic amphibians, Xenopus laevi, and Xenopus tropicalis, are being used as a model system for these investigations. The broad objective of this research is to gain an integrated view of the development and proliferation of sensory hair cells of the inner ear by using multidisciplinary approaches that draw on techniques from biophysics, anatomy, tissue culture, and molecular biology. A major long term goal of our research is to understand the genetic basis of hair cell function, differentiation, and regeneration.
As part of this effort we seek to gain an integrated view of sensory organ formation during inner ear development, and to identify novel genes expressed in the developing auditory and vestibular system.
Experiments underway in the laboratory are testing several hypotheses about the expression of ion channel genes during development, and about the mechanisms that produce functionally heterogeneous hair cells in mature inner ears. For example, in some experiments, we are determining whether endorgans of the inner ear that are responsive to stimuli of different frequencies have hair cells with different types and complements of ion channels for calcium and potassium ions. Our research uses molecular approaches to clone the genes for calcium and potassium ion channels, cytoskeletal proteins, and cell adhesion molecules expressed in the ear. An emerging body of data indicate that these types of proteins may interact in novel and complex ways in cells of the nervous system. We rely on RT-PCR methods to clone genes expressed in the inner ear, and use antibodies to confirm protein expression using methods that rely on immunodetection. As part of this effort, gene expression patterns in the developing auditory and vestibular system are visualized in sectioned and whole mount tissue with in situ hybridization and immunohistohemical techniques. Furthermore, multi-photon and confocal fluorescence microscopy are being used to gather information about cell structure and gene expression. The digitized data can be processed to render tridimensional images of developing inner ear endorgans. Presently an in vitro culture system is being developed that will be used to test hypotheses about hair cell differentiation and regeneration. Cell lines are being used as heterologous expression systems to investigate the function of genes of interest.
The knowledge gained from this research should prove useful in developing treatments for hearing and balance disorders based on hair cell and eighth nerve dysfunction, particularly those caused by trauma, or those with a genetic basis.