A nonsense mutation in the gene encoding a zebrafish myosin VI isoform causes defects in hair-cell mechanotransduction

In a three-gene ration screen of chemically mutagenized zebrafish, we identified a group of mutations that affect the development and function of hair cells, the mechanically sensitive cells of the inner ear and lateral-line organ. One mutant line, ru920, was discovered in a behavioral screen for defects in the acoustically evoked escape response. Despite apparently normal numbers of hair cells, mutants lack an inner-ear microphonic potential and exhibit reduced labeling of hair cells by a fluorophore that traverses transduction channels. This hair-cell-specific phenotype suggested a defect in the mechanoelectrical transduction apparatus. Positional cloning revealed that the recessive mutation introduces a premature stop codon in the ORF of myosin6b (myo6b), one of the two zebrafish orthologs of the human gene myosin VI. The ru920 line therefore provides an animal model with which to study the role of class VI myosin proteins in mechanotransduction.