Figure 1.
Elimination of SNAP-25 leads to impaired neuronal survival and outgrowth. A, Double staining for SNAP-25 (or SNAP-23) and synaptophysin as a synaptic marker of primary cultured hippocampal neurons infected with recombinant lentiviruses. A synapsin promotor was used to restrict eGFP expression to neurons and enable morphological analysis (left column). This revealed inferior outgrowth/branching in Snap-25 null (−/−) neurons compared with control (+/+; +/−). Nevertheless, neurons lacking SNAP-25 still formed synaptophysin-positive synapses. Expression of SNAP-25a, SNAP-25b, or SNAP-23 in Snap-25 null neurons recovered the morphology. B, Left, The number of cells (mean ± SEM) present after 10–14 d in culture. Survival of null neurons was dramatically reduced but rescued with SNAP-25a, SNAP-25b, or SNAP-23 expression. Right, The number of branches (mean ± SEM) as a function of distance to the soma. Neurite extension in surviving Snap-25 null neurons was significantly depressed (***p = 0.001, Student's t test) compared with control neurons or null neurons rescued with SNAP-25a, SNAP-25b, or SNAP-23.