EXCEED THE SPACE PROVIDED. Many inherited and acquired conditions involving deafness and loss ofbalance are due to defects in, or damage to, the sensory and support cells of the inner ear, but our molecular understanding of these and other mechanosensory cells is limited. This proposal focuses on the discovery and functionalanalysis of novel proteins required for sense organ differentiation or operation. Drosophila brings powerful genetic and molecular model system to the study of mechanosensory proteins. Fliesbear ciliated sense organs that are amenable to optical imaging and electrophysiological recording; they also show striking developmental and functional similarities to the sensory elements of the vertebrate inner ear. Positional cloning is used to isolate genes previously identified in behavioral and electrophysiological mutant screens. Transgenic animals and enable the location and function of normal and modified gene products to be tested in situ; this is particularly important because mechanosensitivity may not be reconstituted in heterologous systems. Several genes required for transduction of auditory and tactile stimuli have been identified bybehavioral mutations. Two of the affected genes were cloned and described, and the encoded proteins located by fluorescence tagging. nompA encodes a component of the dendritic cap, an extracellularstructure that links neuronal sensory processes to the stimulating cuticular structures. It shows structural similarities to tectorins, proteins that play an analogous role in the vertebrate inner ear. uncoordinated encodes a novel coiled-coil protein that is localized in differentiating sensory neurons to the basal body, the structure that gives rise to the ciliary sensory endings. It is the first known molecular marker for the centriole-basal body transition. It is next proposed to establish the exact function of these gene products by identifying domains within the Unc and NompA proteins that determine their localizationand function. Such domains will be used to search for other interacting proteins. A model for the synthesis and extracellulardeposition of NompA and similar proteins will be tested. The ultrastructural nature of the defects in the unc and nompA mutant sense organs will be investigated. At least two more proteins will be similarly identified and characterized, beginning with those encoded by the rempA and nompB genes. PERFORMANCE SITE ========================================Section End===========================================
