Tiam1 knockdown increases dendritic spine length in DG granule neurons, but not in CA1 pyramidal neurons. A, D, Schematic representation of areas of image acquisition from DG granule neuron dendrites and apical CA1 pyramidal neuron dendrites, respectively. B, E, Representative dendritic segments and corresponding reconstructed segments from GFP and Tiam1 shRNA-expressing DG granule neurons and CA1 pyramidal neurons. Scale bars, 4 μm. C, F, Boxplots show significant differences in spine length and spine neck length in DG granule neurons expressing Tiam1 shRNA (colored boxes) compared with GFP-expressing control neurons (gray boxes; p = 0.00024 for spine length; p = 0.0014 for spine neck length; for GFP, n = 19 segments; for Tiam1 shRNA, n = 17 segments), no significant differences in head volume or spine density were detected (p = 0.9 for head volume; p = 0.6 for spine density; for GFP, n = 19 segments; for Tiam1 shRNA, n = 17 segments). No significant differences were detected in any spine parameters in Tiam1 shRNA-expressing spines in CA1 pyramidal neurons compared with corresponding GFP-expressing control neurons (for GFP, n = 12 segments; for Tiam1 shRNA, n = 25 segments; p = 0.26 for spine length; p = 0.55 for spine neck length; p = 0.17 for head volume; p = 0.7 for spine density; Wilcoxon rank-sum test) ***p < 0.001, **p < 0.01, Wilcoxon rank-sum test. n.s., Not significant.