a, Mean ABR thresholds were significantly reduced at three frequencies in ears injected with Cas9–Tmc1-mut1–lipid compared to uninjected Tmc1Bth/+ ears after four weeks. b, DPOAE thresholds were elevated in the same group of inner ears after Cas9–Tmc1-mut1 injection as in a after four weeks. c, Mean ABR thresholds were significantly reduced at five frequencies in ears injected with Cas9–Tmc1-mut2–lipid compared to uninjected Tmc1Bth/+ ears after four weeks. d, DPOAE thresholds were elevated in the same group of inner ears after Cas9–Tmc1-mut2 injection as in c after four weeks. e, Mean ABR thresholds were significantly reduced at three frequencies in ears injected with Cas9–Tmc1-mut4–lipid compared to uninjected Tmc1Bth/+ ears after four weeks. f, DPOAE thresholds were elevated in the same group of inner ears after Cas9–Tmc1-mut4–lipid injection as in e after four weeks. g, Significantly stronger wave 1 amplitudes were detected in ears injected with each of the Cas9–Tmc1-mut–lipid complexes shown at 16 kHz (80 and 90 dB SPL). Individual values (n = 8, 13, or 18) are shown; horizontal bars represent mean values. h, Eight weeks after Cas9–Tmc1-mut1–lipid injection into Tmc1Bth/+ ears, mean ABR thresholds were significantly reduced at five frequencies compared to uninjected Tmc1Bth/+ ears, which showed ABR thresholds >80 dB at all frequencies after eight weeks. Mean ABR thresholds of untreated wild-type (WT) C3H mice of eight weeks of age are shown in purple. Red arrows indicate no ABR response at the highest SPL level of 90 dB. i, DPOAE thresholds were significantly elevated at two frequencies (8 and 11 kHz) in the same group of inner ears after Cas9–Tmc1-mut1 injection as in h after eight weeks. Mean DPOAE thresholds of untreated wild-type C3H mice of eight weeks of age are shown in purple. Statistical analysis of ABR and DPOAE thresholds and wave 1 amplitudes was performed by two-way ANOVA with Bonferroni correction for multiple comparisons: *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Values and error bars reflect mean ± s.e.m. Among the different frequencies assayed, the number of ears tested (n) varies within the range shown (Supplementary Table 2).