Figure 4. MMP‐9 activity at dendritic spines and analysis of dendritic spine morphology.

1. Exemplary images from FITC‐tagged gelatin (DQ‐gelatin) assay showing colocalization map of FITC fluorescence that corresponds to gelatinolytic activity. Red fluorescent protein was used to label cell morphology, showing a short stretch of dendrite that overexpressed either the MMP‐9_C or MMP‐9_T variant. Warmer colors correspond to higher gelatinolytic activity. Dendritic spines with an increase in gelatinolytic activity are marked with arrows.
2. Quantification of analyzed data from four separate experiments. The relative increase in fluorescence was measured for individual spines over time as a readout of MMP‐9 activity. A total of 17 cells (MMP‐9_C) or 13 cells (MMP‐9_T) were analyzed.
3. Image from morphological analysis of spines from primary rat hippocampal neurons showing example of mushroom and thin spine shapes.
4. The rs20544 polymorphism influenced the percent distribution of spine shape. Quantification of percent distribution of mushroom and thin spines from time‐lapse imaging from three separate experiments. Neurons that overexpressed MMP‐9_C had more mushroom spines and less thin spines than the MMP‐9_T variant. For each polymorphic variant, six cells were analyzed; the total number of spines analyzed was n _spines = 419 for MMP‐9_C and n _spines = 465 for MMP‐9_T.

Data information: Error bars indicate the SEM. *P < 0.05, **P < 0.01, ***P < 0.001 (Mann–Whitney U‐test in B; two‐way ANOVA with multiple comparisons in D).