GENETIC-ANALYSIS OF VERTEBRATE SENSORY HAIR CELL MECHANOSENSATION - THE ZEBRAFISH CIRCLER MUTANTS

The molecular basis of sensory hair cell mechanotransduction is largel y unknown. In order to identify genes that are essential for mechanose nsory hair cell function, we characterized a group of recently isolate d zebrafish motility mutants. These mutants are defective in balance a nd swim in circles but have no obvious morphological defects. We exami ned the mutants using calcium imaging of acoustic-vibrational and tact ile escape responses, high resolution microscopy of sensory neuroepith elia in live larvae, and recordings of extracellular hair cell potenti als (microphonics). Based on the analyses, we have identified several classes of genes. Mutations in sputnik and mariner affect hair bundle integrity. Mutant astronaut and cosmonaut hair cells have relatively n ormal microphonics and thus appear to affect events downstream of mech anotransduction. Mutant orbiter, mercury, and gemini larvae have norma l hair cell morphology and yet do not respond to acoustic-vibrational stimuli. The microphonics of lateral line hair cells of orbiter, mercu ry, and gemini larvae are absent or strongly reduced. Therefore, these genes may encode components of the transduction apparatus.