Fig. 6: ECM accumulation blunted experience-dependent synaptic change.
From: Extracellular matrix proteolysis maintains synapse plasticity during brain development
a, Schematic of the forced swim paradigm performed in this study. Forced swim (FS) groups were put on a Petri dish with a stirrer bar and exposed to water current for 8 h per day at 650 rpm, for 2 consecutive days. Control (CT) groups were put in a Petri dish without stirrer bars. Experiments were performed at 13–14 dpf. b, Representative images of brevican staining in CT and FS groups. c, Quantification of brevican intensity in synaptic region normalized to mean of CT group (CT, n = 16 fish; FS, n = 16 fish; **P = 0.0021, Welch’s t-test). d, Representative images of Chat-PSD95FingR dendrites from fixed sections stained for TdT in FS or CT group. e, Quantification of excitatory synapse density (Chat-PSD95FingR puncta) per µm of dendrite length in FS or CT group. Dots represent means per fish from n = 1–4 dendritic segments analyzed per fish (CT, n = 39 dendrites from n = 25 fish; FS, n = 34 dendrites from n = 23 fish; *P = 0.026, Welch’s t-test for fish). f, Schematic of time-lapse synapse imaging performed before (t = 0) and after (t = 30) forced swim paradigm. Experiments were performed at 10–12 dpf. g, Representative merged images of time-lapse assay in the Chat-PSD95FingR before (t = 0, pink) and after (t = 30, green) forced swim paradigm or control. Pink arrowheads, lost synapses; green arrowheads, new synapses. Nonmerged images are shown in Extended Data Fig. 10a. h, Quantification of newly observed, lost and stable synapses after forced swim paradigm (CT, n = 8 fish; FS, n = 9 fish; **P = 0.0060 for newly observed, P = 0.140 for lost, P = 0.507 for stable, Welch’s t-test). i, Representative images of brevican staining in mmp14b−/− fish from FS or CT group. j, Quantification of brevican intensity in synaptic region in mmp14b−/− fish normalized to CT group (CT, n = 13 fish; FS, n = 11 fish; P = 0.397, Welch’s t-test). k, Representative images of Chat-PSD95FingR dendrite in mmp14b−/− fish from FS or CT group. l, Quantification of synapse density (Chat-PSD95FingR puncta) per µm of dendrite length from FS or CT group in mmp14b−/−. Dots represent means per fish from n = 1–4 dendritic segments analyzed per fish (CT, n = 20 dendrites from n = 13 fish; FS, n = 27 dendrites from n = 16 fish; P = 0.48, Welch’s t-test for fish). m, Representative merged images of time-lapse assay in the Chat-PSD95FingR;mmp14b−/− fish before (t = 0, pink) and after (t = 30, green) forced swim paradigm or control. Pink arrowheads, lost synapses; green arrowheads, new synapses. Nonmerged images are shown in Extended Data Fig. 10b. n, Quantification of newly observed, lost and stable synapses after forced swim in the mmp14b−/− fish (CT, n = 14 fish; FS, n = 13 fish; P = 0.542 for newly observed, P = 0.621 for lost, P = 0.690 for stable, Welch’s t-test). Values were plotted as mean ± s.e.m. **P < 0.01; *P < 0.05. Scale bars, 20 µm (b,i), 5 µm (d,g,k,m).
