Supplementary Figure 3: SLM single and compound spine morphology; related to Fig. 3.
From: Single excitatory axons form clustered synapses onto CA1 pyramidal cell dendrites
(a) Left, mean spine volume from single synapses (orange, from n = 195 reconstructed spines) and compound synapses (blue, from n = 56 reconstructed spines) (***p < 0.0001, Mann-Whitney test). Right, mean PSD area for the same spines (**two-sided Mann-Whitney test, p = 0.007). Data represent mean ± SEM. (b) Left, relationship between spine volume and spine neck diameter for single (orange, from n = 195 reconstructed spines) and compound synapses (blue, from n = 56 reconstructed spines) (single: Spearman’s correlation, r = 0.31, p < 0.0001; compound: Spearman’s correlation, r = 0.12, p = 0.37; difference between best-fit slopes, p = 0.25). Center, mean spine neck diameter (two-sided Mann-Whitney test, p = 0.32, data represent mean ± SEM.). Right, histogram showing the percentage of spine neck diameters from single (orange) and compound (blue) connections (Χ2 test, p = 0.55). Inset, cumulative frequency plot (two-sided KS test, p = 0.46). (c) Left, a spine (yellow; from n = 251 reconstructed spine synapses) containing both a perforated PSD (denoted by arrowheads) and a spine apparatus (denoted by arrows). Center, cumulative frequency plot of volumes from spines with or without a perforated PSD (two-sided KS test, p < 0.0001). Right, cumulative frequency plot of volumes from spines with or without a spine apparatus (two-sided KS test p < 0.0001). (d) Percentage of single or compound dendritic spine synapses that contain a perforated PSD, a spine apparatus, both, or neither (from n = 195 reconstructed single connection spines and n = 56 compound connection spines). (e) A table of spine morphological parameters (from n = 195 single connection spines and n = 56 compound connection spines).
