examination of the process of experience dependent modification (or plasticity) of synapses at the cellular and molecular levels

David Wells, Ph.D. Associate Professor of Molecular, Cellular and Developmental Biology Email: david.wells@yale.edu B.A. University of Vermont 1986; Ph.D. University of Vermont 1994

			Hippocampal neuron grown in culture and processed for immunocytochemistry to determine the location of synaptic connections. Using this method we can determine if a protein or mRNA is localized at synapses. For example, by utilizing this in combination with in situ hybridization, we can determine if specific mRNAs are located near synapses and thus would make likely candidates for local mRNA translation regulation.

The formation and maintenance of memories is one of the brains most intriguing functions. Somehow encoded into the neural circuitry is the ability to store and retrieve experiences for years or even decades. Since synaptic transmission encodes information in the brain, the engram for memory may lie in the ability of the synapse to use stable modifications to remember its excitatory history. The focus in our lab is to examine this process of experience-dependent modification (or plasticity) at the cellular and molecular level.

A critical step in long-lasting synaptic plasticity is the production of new proteins. Synapses undoubtedly use proteins that are generated in the cell body and subsequently transported into the dendrites; however, there is increasing evidence that local (dendritic or even synaptic) protein synthesis plays a crucial role in long-lasting synaptic changes. We have known for over 20 years that mRNA is present in dendrites, but mechanism(s) for translational regulation are only now being elucidated.

Our lab examines a molecular mechanism capable of regulating mRNA translation in dendrites. This process is dependent on an mRNA binding protein called CPEB that is present in neurons and localized to synapses. CPEB was first described in Xenopus oocytes where it regulates mRNA translation through poly(A) tail elongation. We have shown that polyadenylation of specific messages in the visual cortex and hippocampus occurs following neural activity and is concomitant with an increase in the encoded protein at the synapse. Our lab is currently studying this mechanism in neurons throughout the brain to determine if this process is a general mechanism for experience dependent plasticity.

We use a combination of molecular, cellular and electrophysiological techniques to address how CPEB-mediated protein synthesis is initiated and what mRNAs this process regulates.

Selected Publications

Shin, C.Y., Kundel, M., and Wells, D.G. (2004) Rapid activity-induced increase in tissue plasminogen activator is mediated by metabotropic glutamate receptor-dependent protein synthesis. J. Neurosci. 24:9425-9433.

Osterweil, E., Wells, D.G. and Mooseker M.S. (2005) A role for Myosin VI in postsynaptic structure and glutamate receptor endocytosis. J. Cell Biology 168(2):329-38.

McEvoy, M., Cao, G., Llopis, P., Kundel, M., Jones, K., Hofler, C., Shin, C. and Wells, D.G (2007) CPEB1-mediated mRNA translation in Purkinje neurons is required for cerebellar long-term depression and motor coordination. J. Neurosci. 27:6400-11.

Jones, K.J., Korb, E., Kundel, M.A., Kabraji. S., Kochanek, A.R., Shin, C.Y., and Wells,D.G. (2008) CPEB1 Regulates beta-Catenin mRNA Translation and Cell Migration in Astrocytes. Glia 56:1401-1413.

Aslam, N., Kubota, Y., Wells, D., and Shouval, HZ (2009) Translational switch for long term maintenance of synaptic plasticity. Molecular Systems Biology 5:284.

Kundel, M.A., Jones, K.J. Shin, C.Y.and Wells, D.G. (2009) Cytoplasmic polyadenylation element binding protein regulates neurotrophin 3-dependent beta-catenin mRNA translation in developing hippocampal neurons. J. Neurosci. 29:13630-9.

			Hippocampal neurons grown in culture and transfected with either a construct encoding green fluorescent protein (GFP) alone (left) or a synaptic protein fused with GFP (right). GFP is expressed throughout the cell and allows us to visualize the entire cell; however, when GFP is fused to a synaptically expressed protein it appears as puncta that we can follow with high-resolution video microscopy.

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