(A) Quantification of RIBEYE, GluA3 and CaV1.3 puncta in the organ of corti normalized to the number of IHCs in analyzed regions of interest. The number of GluA3 receptor and CaV1.3 puncta is unaffected (p>0.05). WT in blue, n = 9 images from three mice, 95 cells, quantified puncta — RIBEYE = 1456, GluA3 = 1459, CaV1.3 = 1897. KO in red, n = 13 images from three mice, 248 cells, quantified puncta — RIBEYE = 28, GluA3 = 2149, CaV1.3 = 2681. (B) Colocalization of synaptic puncta per IHC. In the absence of RIBEYE, the number of synapses, defined by colocalization of postsynaptic GluA3 and presynaptic CaV1.3, is unaffected (p=0.13) in KO. (C) Volume of presynaptic CaV1.3, Bassoon and postsynaptic Homer and GluA3 in WT (blue, n synapses — CaV1.3 = 1370; Bassoon = 1917; Homer = 5219; GluA3 = 1611) and KO (red, n synapses — CaV1.3 = 2132; Bassoon = 1817; Homer = 4990; GluA3 = 2334) mice. (D) Normalized cumulative distributions of volumes show increased sizes of postsynaptic GluA3 and Homer immunoreactivity. (C) Boxes represent standard deviations of the mean. Significance levels of two-tailed unpaired t-tests (A, B) or two sample Kolmogorov-Smirnov test (C): (D) represents the maximum distance of the Kolmogorov-Smirnov distribution functions. n.s., not significant; *p≤0.05; **p≤0.01; ***p≤0.001; ****p≤0.0001.