Membrane fusion is a biological process central to communication between cells.  The fusion of small vesicles to a neuronal cell membrane during synaptic transmission is a prime example of this process.  While considerable advances have been made in our understanding of this type of membrane fusion, it has proven difficult to study in living systems and the mechanism of vesicle fusion remains largely unknown.

In our lab we have developed a synthetic model system for vesicle fusion which allows us to experimentally interrogate the fusion process in a well-controlled and reliable manner.  We have synthesized lipid-DNA conjugates that can be incorporated into small unilamellar vesicles 50-100 nm in diameter.  The hybridization of complementary lipid-DNA conjugates on apposing vesicles can be used to mediate docking [251] and fusion [258], [261] between those vesicles, as shown in the figure above.  Using this model system, we have been able to observe lipid mixing and content mixing in the bulk phase as vesicle fusion occurs and have been able to address how the number density and geometry of DNA partners affects those processes.

Our synthetic lipid-DNA conjugates can also be used to tether small vesicles to a supported lipid bilayer. [217], [227], [235], [237]  The vesicles are laterally mobile and can be visualized with fluorescence microscopy.  Our current work involves developing an approach to reliably visualize DNA-mediated docking and fusion between individual vesicles tethered to a supported bilayer.  This will allow us to observe DNA-mediated vesicle fusion on a single event level and will provide us with an excellent tool to address important questions surrounding vesicle fusion.

"Covalent Attachment of Lipid Vesicles to a Fluid-Supported Bilayer Allows Observation of DNA-Mediated Vesicle Interactions", Bettina van Lengerich, Robert J. Rawle, and Steven G. Boxer, Langmuir, in press. [pdf]

"Effects of Linker Sequences on Vesicle Fusion Mediated by Lipid-Anchored DNA Oligonucleotides", Yee-Hung M. Chan, Bettina van Lengerich, and Steven G. Boxer, PNAS, 106, 4, 979-984 (2009). [pdf]

"Lipid-anchored DNA Mediates Vesicle Fusion as Observed by Lipid and Content Mixing", Yee-Hung M. Chan, Bettina van Lengerich, and Steven G. Boxer, Biointerphases, 3, 2, FA17-FA21, (2008). [pdf]

"Kinetics of DNA-mediated Docking Reactions Between Vesicles Tethered To Supported Lipid Bilayers", Yee-Hung M. Chan, Peter Lenz, and Steven G. Boxer, PNAS, 104, 48, 18913-18918 (2007). [pdf]