Hair cells in tmc1/2a/2b triple mutants lack mechanosensitivity. A, The amplitude of microphonic potentials correlates with stimulus intensity in WT siblings; however, tmc1/2a/2b triple-mutant larvae (3 dpf) have no detectable microphonic potentials, even with high-intensity stimuli (n = 9 for each genotype; F(1,16) = 32.3). B, Otocyst injection of FM 1-43 vital dye, which labels hair cells with intact MET channels, does not label inner ear hair cells in tmc1/2a/2b triple-mutant larvae (6 dpf), further demonstrating a uniform lack of hair-cell activity in all end organs. Side view of inner ear is shown. *Injection damage. AC, Anterior crista; LC, lateral crista; PC, posterior crista; AM, anterior macula; PM, posterior macula. Scale bar, 50 μm.