Figure 4. Loss of sensory transduction, not of Tmc1 and Tmc2 specifically, results in the synaptic differences observed at postnatal day 7 (P7) and P28.

(A–C) The mean number of synapses/inner hair cell (IHC) at each frequency region. Data from wild-type (WT) (black), Tmc1^Δ/Δ;Tmc2^Δ/Δ (red), Tmc1^Δ/Δ (blue), Tmie^sr (purple), and Tmc1^Bth (gold) groups are shown. WT, Tmc1^Δ/Δ, and Tmc1^Δ/Δ;Tmc2^Δ/Δ data are the same as those depicted in Figure 3, reprinted here to facilitate comparison. Individual points represent counts from one mouse. In A and B two-way interactions between genotype and timepoints were statistically significant for all frequencies based on two-way ANOVA (p < 0.001; Supplementary file 3B), suggesting the trajectory of synaptic development varies by genotype. The genotype-specific trajectory of synaptic development did not vary by frequency (three-way ANOVA; p = 0.68 based on three-way interaction between genotype, timepoints, and frequency; Supplementary file 3B). Frequency-specific synapse counts differed by genotype in C (two-way ANOVA; p = 0.002 based on two-way interaction between genotype and frequency; Supplementary file 3B). Bolded lines depict mean ± SD. Black horizontal bars and asterisks represent statistically significant differences in group means (multiple pairwise comparisons, *p < 0.05, **p < 0.01, ***p < 0.001; exact p values listed in Supplementary file 4A-C). Number of cochleas: 4 WT, 5–12 Tmc1^Δ/Δ;Tmc2^Δ/Δ, 4 Tmc1^Δ/Δ, 5–6 Tmie^sr, 4–6 Tmc1^Bth.