SUMMARY The long-term goal of my laboratory is to elucidate the mechanisms that regulate the development and function of hair bundles of cochlear hair cells, and how defect in hair bundles cause disease. We propose here to study the function of two genes, clarin1 (CLRN1) and clarin2 (CLRN2) that have been linked to hearing loss. Mutations in the murine Clrn1 and Clrn2 genes cause defects in hair bundle development and MET. We hypothesize that CLRN1 and CLRN2 form protein complexes with proteins that have previously been linked to hair bundle development and MET to affect the development and function of hair cells. To test our hypothesis, we will use genetically modified combined with immunohistochemistry, electron microscopy as well as biochemical, cell biological and electrophysiological methods to study CLRN1 and CLRN2 function in hair cells. Our preliminary data show the feasibility of our approach. We have identified CLRN1 and CLRN2 binding partners that are encoded by genes linked to deafness and our findings suggest that these bindings partners act in concert with CLRN1 and CLRN2 to regulate hair cell development and function.