The movie begins with three compartments, or vacuoles, docked like nanometer-sized flying saucers inside a yeast cell. The boundary membranes, which look like interior walls, are where the three vacuoles meet. Suddenly, they break loose, flapping inside the outer membrane in what has become a single organelle. This is membrane fusion—essential for transferring chemical information inside cells—and, until now, nobody knew how it happened. The previous model of a radially expanding pore was unexpectedly replaced by this mechanism called vertex ring fusion by its discoverers, William Wickner, Dartmouth Medical School biochemistry professor, and colleagues. Using time-lapse fluorescence microscopy, they demonstrated that boundary membrane is released from the vertices, or junctures of boundary and exterior membranes (L. Wang et al., "Vacuole fusion at a ring of vertex docking sites leave membrane fragments within the organelle," Cell, 108:357-69, Feb. 8, 2002). Nobody yet knows what happens to the released membrane after...

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