FIGURE 4:

The Sec14 domain of Kal7 plays a role in determining spine length. Top, diagrams illustrating the proteins expressed. Hippocampal neurons prepared from P0 rat embryos were doubly transfected with vectors encoding MycKal7 and GFP (A) or HA₂-ΔSec14-Kal7 and GFP (B) or transfected with vector encoding a KalSec14-GFP fusion protein (C) at the time of plating. Neurons were visualized for GFP and Myc (HisMycKal7) or HA (HA₂-∆Sec14-Kal7) (red) at DIV13, a time at which endogenous Kal7 is barely detectable (Ma et al., 2008a). (D) Spine density was indistinguishable in neurons expressing Kal7 and ΔSec14-Kal7 but was significantly lower in Sec14-GFP–expressing neurons (t test); synaptic density is lower here than in Figure 3 because synapse formation is not complete in DIV13 neurons. (E) Quantification of spine length revealed that ∆Sec14-Kal7 produced significantly shorter spines than MycKal7 (p < 0.01), whereas Sec14-GFP produced aberrantly long spines (p < 0.05).