Figure 3.

Altered presynaptic Ca²⁺ channel clusters and near normal postsynaptic AMPA receptor clusters at IHC synapses of Bsn mutants. A, Ca_v1.3 immunofluorescence in Bsn^gt IHCs (violet, n = 108 Bsn^gt ribbonless synapses; red, n = 108 Bsn^gt ribbon-occupied synapses) had reduced intensity compared with WT_gt (black, n = 105 synapses). The analysis shown is derived from one representative pair of triple-stained samples as shown in Figure 1. Ribbon-occupied BSN^gt synapses harbor more Ca_v1.3 immunofluorescence than ribbonless synapses but less than WT_gt. B, Pair of double-stained preparations demonstrating the reduction in synaptic Cav1.3 (green), but not GluA2 receptor (blue), immunofluorescence. C, Distributions of GluA2 cluster immunofluorescence intensities of Bsn^gt and WT_gt synapses overlapped (same preparation and color-codes as in A. D, Stimulated emission depletion microscopy demonstrating that ribbon-occupied and ribbonless synapses retained the ring-like morphology of GluA2/3 clusters (blue) in Bsn^ΔEx4/5 synapses, albeit with a slightly smaller diameter in the absence of a presynaptic ribbon (CtBP2, red, confocal mode).