Aryeh Routtenberg - US grants

Rapid post-translational modification of brain phosphoproteins may mediate the rapid onset of synaptic modifications that underlie synaptic plasticity. The phenomenon of long-term potentiation (LTP) involves a rapid dramatic change in synaptic activation which is persistent for days or even months. Because of its relation to models of information storage and memory we propose to suty the effect of LTP on specific identifiable brain phosphoproteins, to determine their particular role in LTP. We propose to study those phosphoproteins whose identity or regulators is known, but whose role in synaptic modification is not. By using different methods to preserve the in vivo state of these proteins, it is possible to determine whether LTP increases or decreases the state of phosphorylation of a specific protein. Because LTP can be controlled, both with regard to extent and time course (up to 3 months in long term studies) phosphoprotein metabolism important for LTP can be identified. The identification of those proteins important for regulating information flow and registration in the central nervous system may provide new insights into diseases of memory such as presenile dementia of the Alzheimer's type.

Abstract for Lay Audience -Routtenberg

Perhaps the most unnerving experiences in our intellectual lives is
the frustration of forgetting. It is the over-arching view of the proposed
research that 'why we forget' has to do with the faulty chemistry of the
brain connections that form the memory network. Indeed we have recently
discovered using a model system of brain memory that we can prevent memory
storage and its retrieval. Then, by giving a drug that activates a
signalling pathway that our laboratory described, we can reactivate the
memory. Put another way, the key that turns on memory and its retrieval
may be like that used in the car's ignition. What we have done is moved to
the next stage and 'hot-wired' memory processes, by-passing the initial
switch. This pathway is thus critical to memory formation and retrieval.
Our studies employ gene targeting methods in transgenic mice to
modify the switches and signalling mechanisms (gene products or proteins,
one and all) that regulate both the chemistry of the brain connections and
as a consequence the memory storage process. We study the most widely used
physiological model of memory, long-term potentiation, which monitors the
events that occur at the synapse at the time when model memories are being
stored. We complement the gene targeting with pharmacological tools that
allow us to confirm with converging lines of evidence the identified
sequence of events involved in the storage of information. Since gene
manipulation is not feasible in humans, this complimentary approach
provides the basis for drug discovery in the context of current molecular
biological technologies and suggest novel strategies in the war against
cognitive and memory disorders.

The proposed research is directed at the study of growth-associated protein GAP-43, an essential presynaptic protein with critical functions in neural development (axonal pathfinding), and plasticity (long-term potentiation, learning and memory). Because GAP-43 is central to plasticity mechanisms, brain site-selective manipulations targeting GAP-43 in a temporally and spatially controlled fashion can offer unique insights into memory acquisition, storage and recall. GAP-43 is critical for brain development as its knockout is perinatal lethal probably because the null mutation disrupts synaptic targeting (see Benowitz and Routtenberg, 1997, for review). GAP-43 bidirectionally regulates adult memory: reduction by half impairs (Rekart et aI., 2005), while its overexpression can enhance (Routtenberg et aI., 2000), information storage processes. The proposed research tests the over-arching Aim that in wild type animals the level of endogenous phosphorylatable GAP- 43 plays a pivotal role in regulating brain information storage. Evidence in support of this hypothesis has been gained in transgenic animals, yet no information is currently available as to the site specificity of the phenotype. The specific questions we will address are: What level of region-specific knockdown in GAP-43, using RNAi methods, in adult wild type rodents will impair acquisition or retention of 3 different learning tasks? The siRNA will be delivered using lipofectamine or lentiviral transfer, with bilateral intracranial injections targeting hippocampus, amygdala, anterior cingulate cortex or medial prefrontal cortex. We will thus determine the kinetics of this silencing using RNAi methods to deliver the knockdown targeting nodal points in the 'memory circuit'at different time points in the learning and retention process to pinpoint the mnemonic function served by GAP-43 in each brain location.

DESCRIPTION (provided by applicant): The Neurobiology of Information Storage Training Program (NISTP) is based in the Northwestern University Interdepartmental Neuroscience program (NUIN), emerging from within a multidisciplinary group of highly interactive investigators who have carried out research at different levels, and have successfully engaged in collaborative research on cellular, molecular, structural, network and system determinants of information storage. After the first 2 cycles of NIMH-supported training grant activity it is clear that NISTP is part of the fabric of the neuroscience community at Northwestern. Since its inception in 2003, NISTP has evolved by continually adding elements that enrich the training experience. Training includes a formal didactic component in the form of a special course focusing on the latest research in information storage neurobiology, three special lecture series each with the purpose of bringing the most outstanding scientists to interact with the trainees, a mock study section which provides both professional training and is a springboard for submission of an NRSA proposal (a NISTP requirement), the annual retreat that fosters a wide-range of survival skills with maximum trainee - faculty interaction, two different journal clubs reviewing recent research in the neurobiology of information storage, and a 'Buddy Program' that encourages trainees to see the 'bench-to-bedside' application of their fundamental research. With these value added components, we believe that trainees emerge from the training program both poised to advance research in fundamental biological mechanisms of learning and memory and well-positioned to develop novel translational applications.