Karen Greif

Education

      A.B. in Human Biology, Brown University, 1973
      Ph.D. in Psychobiology and Biochemistry, California Institute of Technology, 1978

Research Interests

I am studying the roles of proteins involved in synaptic transmission during early neurite development in vitro, using rat sympathetic neurons and embryonic chicken neurons as model systems. 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. Monoclonal antibodies are used as probes for cell surface and vesicular antigens, using immunocytochemical methods. 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 over-express the fusion protein and transport it similarly to native proteins. RNA interference is used to knock down protein levels. We have demonstrated that levels of synaptotagmin 1 (syt1), the main calcium sensor at the synapse, influence filopodia and branches on chick embryo forebrain neurons. Our working hypthesis is that in response to local calcium signals, syt1 mediates addition of membrane to the cell surface to facilitate filopodial development and hence axon branching.

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 has been published by MIT Press.

syt1 distribution along axons

 

Syt1 is concentrated along axons where filopodia are present and/or initiated. Live E8 chick forebrain neurons expressing a syt1-YFP construct were imaged for 5 minutes. (A) "Hot spots" of syt1 are observed inregions with many filopodia. (B) Syt1 fluorescence can be seen moving into the developing filopodium. (c) Analysis of syt1 distribution shows that there is significantly more syt1 fluroescence in regions of axons with filopodia than in regions lacking filopodia. Magnification 1000X. Image taken from Greif et al, Dev. Neurobiol, 2013

 

 

Courses Taught

Biology 110: Biological Explorations I --The Biology of Cancer

Biology 202:  Introduction to Neuroscience
Biology 210: Biology and Public Policy

Biology 340: Cell Biology

Biology 364: Developmental Neurobiology

Biology 395: Senior Seminar in Cell Biology

Biology 396: Topics in Neural and Behavioral Sciences

Biology 398: Senior Seminar in Science and Society

 

Some More Recent Publications

Articles
  • 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)
  • Greif, K.F. 2007. Can we model a cell? Emergent approcches to biological research. Soundings 90:91-101 (publsihed on-line Dec 2007).
  • Greif, K.F., N. Asabere*, G. J. Lutz and G. Gallo. 2013. Synaptotagmin-1 promotes the formation of axonal filopodia and branches along the developing axons of forebrain neurons, Devel. Neurobiology, 73(1):27-44. (Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/dneu.22033, July 27, 2012)

Abstracts

  • 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
  • Greif, K.F., F. Badiane*, K. Krasnec*, S. Chan*, S. Jackson* and N. Asabere*. 2007. Knockdown of synaptotagmin by RNAi influences axon outgrowth in sympathetic neurons in vitro, American Society for Cell Biology Annual Meeting Program #1277.
  • Greif, K.F., N. Asabere*, G. J. Lutz and G. Gallo.2010. Synaptotagmin-1 promotes the formation of axonal filopodia and branches in developing axons. American Society for Cell Biology Annual Meeting, Abstract number #1147.

*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. 2007. Current Controversies in the Biological Sciences: Case Studies of Policy Challenges from New Technologies, Cambridge, MA, MIT Press, 476 pp.