The role of LMTK1A kinase activity in dendritic spine formation. A, The effect of kn LMTK1A on spine formation in vitro. Hippocampal neurons were transfected with GFP and an empty vector (Cont), LMTK1A wt, or kn at 7 DIV and dendritic spines were observed at 18 DIV. Bottom, Higher magnification of the box indicated in top. Scale bars: top, 50 μm; bottom, 10 μm. B, Quantification of the spine density (mean ± SEM, n = 10 for Control; n = 14 for LMTK1A wt; n = 20 for kn). C, The effect of LMTK1A on spine formation in vivo. Neural progenitors were transfected with GFP and an empty vector (Cont) (left), LMTK1A wt (middle), or kn (right) at E14, and dendritic spines were observed at P20. Bottom, Higher magnification of the box indicated in top. Scale bars: top, 50 μm; bottom, 10 μm. D, Spine densities are shown as mean ± SEM (n = 12 for control; n = 10 for LMTK1A wt; n = 11 for kn). *p < 0.05, **p < 0.01, ***p < 0.001.