Lentiviral introduction of SNAP-25 mutants not binding syt-1 rescues cell survival and synapse formation. A, Normalized number of hippocampal neurons counted on glial islands. Between 5 and 18 coverslips were analyzed per condition. B, Western blot of high-density cultures visualizing SNAP-25 endogenous (SNAP-25 WT, gray), Snap-25-null + WT rescue, Snap-25-null + SNAP-25B D186/D193A, Snap-25-null + SNAP-25B D166/E170A, and Snap-25-null + SNAP-25B D51/E52/E55A (all as fusions with EGFP). C, Representative immunocytochemistry images of hippocampal autaptic cultures stained against GFP (green, marker for EGFP-SNAP-25), MAP2 (cyan), and VGLUT1 (red). Image acquisition by confocal microscopy was followed by maximum intensity projection and image analysis. Scale bar, 10 μm. D, Quantification of synapses within 1 μm the dendritic mask. The whole autaptic neuron was analyzed. Bar graph displays mean ± SEM. **p < 0.01 (Kruskall–Wallis test followed by Dunn's post test).