Figure 9.
Effects of increased PSD-95 abundance on innate synaptic molecule dynamics, synaptic size dynamics and size distributions. A, Simulated limiting distributions of synaptic sizes (4000 synapses, last step of simulations) for two levels of global PSD-95 abundance (Ntotal) as indicated at bottom right. Inset, Mean synaptic size during last 72 simulation steps. B, Slopes of linear regression lines as in Figure 7D for the last 72 simulation steps for the two values of Ntotal; apparent <ϵ> values derived from these data are indicated. Fits using these values of <ϵ> are shown as black dashed lines. C, Coefficients of determination (R2) of linear regression fits as in Figure 7D for the last 72 simulation steps for two Ntotal values. D–F, Magnitude of synaptic size fluctuations in the simulated data for the two values of Ntotal. Averages of SDs, coefficient of variations and range/mean values calculated for all synapses over the last 24 simulation steps. Indicated p values are for t tests assuming unequal variances. G, Simulated FRAP curves for the two Ntotal values (200 synapses, 24 simulation time steps). H, Western blots of total PSD-95 levels in chronically silenced and control networks. Four networks in each condition. I, Average (±SEM) of normalized density of PSD-95 bands in Western blots from silenced and control networks (7 replicates from 2 experiments). Difference was not statistically significant (p = 0.62; t test assuming unequal variances). J, SILAC-based comparisons of synaptic protein abundance in silenced and control preparations. Mean ± SD of estimates from four replicates (or 3 where indicated; numbers in bars, top row). Numbers in bars (bottom row) indicate total number of peptides used to obtain H–M estimates. Legend, Gene name followed by common name.