ER SNARE function is required for NE fusion. NE assembly was examined by mixing interphase cytosol, light membranes, sperm, and an energy regenerating system with buffer, 50 µM dominant-negative αSNAP mutant (αSNAP(L294A)), 20 µM of the cytoplasmic fragment of Bnip1 (cytBnip1), 30 µM of the cytoplasmic fragment of syntaxin 18 (cytStx18), or 70 µM of the cytoplasmic fragment of Use1 (cytUse1). Fluorescently labeled dextran was added to detect nuclei with closed NE. The samples were also stained for membranes and DNA. Bar, 20 µm. The percentage of NE fusion was determined as described in Fig. 8 A and the data plotted are the mean ± SD of three independent experiments. *, P < 0.05; **, P < 0.005; and ***, P < 0.001; Student’s t test.