A limited understanding of cochlear biochemistry has hindered attempts to unravel the biochemical mechanisms directing neuron/hair cell connections. In other tissues, cell adhesion molecules have been implicated in the molecular mechanisms underlying directed axonal growth, fasciculation, intercell recognition and synaptogenesis. Previous work has demonstrated the presence of the cell adhesion molecules N-CAM and L1 in the inner ear. The proposed study asks: What are the roles of N-CAM and L1 in neuronal development in the cochlear? The hypothesis is that the cell adhesion molecules facilitate directed axonal growth and assist in the establishment of correct neuron/hair cell connections in the cochlea.. The developing cochlea from the intact mouse (a preparation with both afferent and efferent connections) and from tissue culture (a purely afferent preparation) will be used in this study. In addition,k two mouse models with impaired neurosensory connections will be studied (the Bronx Waltzer mutant and an experimentally produced hyperthyroid animal). The project aims to identify and attempt to quantitate cell adhesion molecules and their molecular forms in developing cochlea by Western Blot and ELISA analyses; to visualize cell adhesion molecules in developing tissue by immunocytochemistry at the light and electron microscope levels in order to compare their distributions to the known temporospatial development of the cochlear innervation; and to deduce the role of the molecules in vitro with antibody perturbation studies Successful experiments can be expected to 1) identify cell adhesion proteins that may participate in the development of defined morphological arrangements in the cochlea and 2) provide information on their roles in the development. This work is pertinent to the study of the biochemistry of deafness caused by impaired cochlear development.
