Figure 4.

Activity dependent re-organization of Bassoon and PSD95 cluster pairs for different activity promoting stimuli. (A) Cumulative frequency curves of the coupling distance (left) and probability (right) measured for coupled Bassoon and PSD95 clusters in high Mg²⁺/low Ca²⁺ (black, n = 18), 0Mg²⁺/Gly/Bic (green, n = 24), and Glu/Gly (orange, n = 7). n = number of neurons from 2 (Glu/Gly) or 3 (high Mg²⁺/low Ca²⁺, 0Mg²⁺/Gly/Bic) independent neuronal cultures. (B) Histograms of the mean coupling probability per neuron at a given distance in high Mg²⁺/low Ca²⁺ (gray), Glu/Gly (orange), and 0Mg²⁺/Gly/Bic (green). (C,D) Cumulative frequency curves of area (left) and eccentricity (right) of coupled (solid line) and uncoupled (dashed line) Bassoon (C) and PSD95 (D) protein clusters. (E) Scatterplot of the UMAP embedding and (F) corresponding kernel density estimation (KDE) maps of coupled Bassoon clusters in high Mg²⁺/low Ca²⁺ (black), 0Mg²⁺/Gly/Bic (green), and Glu/Gly (orange). Local maxima identifying synaptic (A,C,D) shown are the means (plain and dashed lines) with standard error (shaded area). Statistical difference was accessed using a randomization test (see section Materials and Methods and Supplementary Figures 8, 9). Exact p-values are reported in Supplementary Figures 8, 9 with *p < 0.05, **p < 0.01, and ***p < 0.001.