These studies suggest that some of the extracellular filaments are formed by CDH23 and protocadherin 15 (PCDH15), connecting the kinocilium of the hair cell and stereocilia into the bundle.[15] Mutations in the genes responsible for PCDH15 and CDH23 have been found to cause hearing impairment and balance disorders in both mice and humans.[16]CDH23-related hearing loss is associated with its role in the tip links of the inner ear hair cells. This evidence concerns the gene PCDH15 and Hearing impairment.