Hearing tests indicate progressive hearing loss in mutants.

<p>(<b>A</b>)Representative ABR thresholds (with click) from wild-type B6 (right panel) and mutant <i>Atoh1^trhl/trhl</i>(left panel) mice recorded at 21 days of age (P21); n = 5 were tested for each genotype. Note the differences in threshold, waveform morphology and amplitude of the peaks. The X-axis represents time in milliseconds and Y-axis represents amplitude of the action potentials in microvolts. Each waveform, at a different, declining dB level to examine response, is stacked onto the same graph. The right panel displays a much stronger response to the stimulus and clear waveforms at 70 dB but the left panel does not show a very strong response even at 90 dB. (<b>B</b>)Average of ABR thresholds evoked by 16 kHz pure tone recorded from wild-type and <i>Atoh1^trhl/trhl</i>mice at ages 2, 3, and 8 months (n = 5 for each grouping). ABR threshold was higher for mutant strains and progressively worsened over the measured time period, in comparison to littermates. Error bars represent standard deviation. The graph in (<b>C</b>) showsDPOAE amplitudes in mice of three different genotypes at P80 (n = 10 for each genotype). DPOAE amplitudes of the homozygous mutant mice were undetectable at all frequencies while B6 +/+ mice had normal DPOAE amplitudes. The heterozygous had minor reduction of DPOAE amplitudes at 15-20 kHz. Error bars indicate standard error at each time point, for each mouse group.