The overall goal of my research program is to elucidate the underlying molecular principles that govern the assembly of the postsynaptic component of a synapse. There are three main questions we wish to address. First, what are the sequences of events that occur during synapse formation? Second, how does a synapse maintain a stable anatomical identity? Finally, what is the mechanism whereby activity can induce a change in synapse function? To tackle these ambitious goals we use a combination of a number of techniques. The most central to our studies is electrophysiology, since this is the critical and meaningful way to measure the consequences of our molecular manipulations. Our typical assay is to record from a transfected cell that is labeled with GFP and simultaneously from a nontransfected neighboring cell. We stimulate a common bundle of presynaptic axons that synapse onto the pair of neurons and compare the size and properties of the synaptic currents in the two cells. We typically start with the overexpression of a synaptic protein to see if it can modify synaptic transmission. The most critical manipulation is to knock down (shRNA) or delete (genetic deletion in mice) the protein in question. Since many of the proteins of interest are members of a family of related proteins with overlapping function, multiple knock downs/knock outs are often necessary. For this particular renewal we are focusing on two related problems. First, the PSD-95 related MAGUKs, PSD-95 and PSD-93 are structurally very similar and previous findings from my lab had concluded that they had very similar functions. Our more recent data suggest that the role of PSD-93 is intimately dependent on the presence of PSD-95. This is a surprising and intriguing new development and we are in the process of dissecting out this dependence. The second topic involves analyzing the role of neuroligins in the establishment of the postsynaptic density. Current models suggest that neuroligins hold PSD - MAGUKs at the PSD, which in turn holds both the AMPA and NMDA receptors at the synapse. We are currently testing this model as well as a number of other questions that have arisen in our ongoing studies. These projects will provide fundamental knowledge concerning the molecular assembly of the synapse. Since synaptic dysfunction is intimately associated with numerous disease processes, our finding will help shed light on the mechanisms underlying these diseases. More specifically it is well established that mutations in the neuroligins are tightly linked to rare genetic forms of autism.
This research program will elucidate basic mechanisms underlying synaptic communication in the brain. Given the central role of synapses in neurological and psychiatric disease processes the findings from this research will contribute to the development of rational therapies for these diseases.
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