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I am studying the patterns of expression and transport of proteins involved in synaptic transmission during early neurite development in vitro, using rat sympathetic neurons as a model system. Monoclonal antibodies are used as probes for cell surface and vesicular antigens, using immunocytochemical methods. We are especially interested in understanding why these proteins are expressed in developing neurons significantly before synaptogenesis begins, and hypothesize that these proteins may play roles in neurite outgrowth and branching. We also use fusion proteins that couple vesicle-associated proteins to the fluorescent marker, YFP, via a gene construct containing the sequence encoding our protein of interest along with the sequence for YFP. Cells transfected with the construct express the fusion protein and transport it similarly to native proteins.
In addition to my research in cellular neurobiology, I also maintain an active interest in science policy issues. A book exploring the interactions between science and policy in the life sciences is in press from MIT Press.
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Expression of synaptotagmin (red) and syntaxin(green) in neonatal sympathetic neurons after 24 hr in vitro. Synaptotagmin (a synaptic vesicle protein) is transported rapidly to growth cones and varicosities, while syntaxin (a presynaptic membrane protein) is seen only in the cell body and proximal portions of neurites. These observations suggest that different synaptic proteins are transported with different time courses in early neurites.
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Rat sympathetic neurons labeled with synaptotagmin-YFP in vivo after 8 hr in culture. Protein is seen concentrated in cell bodies, growth cones
and varicosities. Many short branches are observed. The fusion protein is transported as soon as neurites develop (from Narayan and Greif, 2004).
Articles:
Greif, K.F. 1994. Expression of pre-proenkephalin mRNA during postnatal development of rat superior cervical ganglion. Neurosci. Lett. 180: 203-208.
Greif, K.F. 1997. Bringing science policy into the classroom: a model course, Politics and the Life Sciences 16 (1): 131-133.
Greif, K.F., C.V. Kuh and J.A. Voytuk. 1997. Career trends for new doctorates in astronomy and astrophysics. Bulletin of the American Astronomical Society. 29(5): 1449-1465. (special volume: the American Astronomical Society’s Examination of Graduate Education in Astronomy)
Greif, K.F. 2001. 3’, 5’-cyclic adenosine monophosphate regulates expression of synaptotagmin in neonatal sympathetic ganglia in vitro, J. Neurobiol., 46: 281-288.
Greif , K.F. 2003. Academics are teachers and colleagues too (letter), Nature 421: 13.
Narayan, S. and K.F. Greif, 2004. Transport of a synaptotagmin-YFP fusion protein in sympathetic neurons during early neurite outgrowth in vitro after transfection in vivo. J. Neurosci. Methods 133: 91-98. (published online 23 December 2003)
Stearns, C.R.*, S. Gu and K.F. Greif. 2005. Differential transport of synaptic proteins in sympathetic neurons in vitro, Neurosci. Abstr. , Program No. 713.2
*Bryn Mawr Undergraduate
Books:
National Research Council (Committee on Dimensions, Causes and Implications of Recent Trends in the Careers of Life Scientists). 1998. Trends in the Early Careers of Life Scientists, Washington DC, National Academy Press, 178 pp
Greif, K.F. and J. F. Merz. 2006. Current Controversies in the Biological Sciences: Case Studies of Policy Challenges from New Technologies, Cambridge, MA, MIT Press, in press.
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