GAP-43 gene expression regulates information storage
Abstract
Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at the behavioral level into “spatial bright” and “spatial dull” groups based on their performance on two hidden platform water maze tasks. G-Phos dull mice showed both acquisition and retention deficits on the fixed hidden platform task, but were able to learn a visible platform task. G-Phos bright mice showed memory enhancement relative to wild type on the more difficult movable hidden platform spatial memory task. In the hippocampus, the G-Phos dull group showed a 50% greater transgenic GAP-43 protein level and a twofold elevated transgenic GAP-43 mRNA level than that measured in the G-Phos bright group. Unexpectedly, the dull group also showed an 80% reduction in hippocampal Tau1 staining. The high levels of GAP-43 seen here leading to memory impairment find its histochemical and behavioral parallel in the observation of Rekart et al. (Neuroscience 126: 579–584) who described elevated levels of GAP-43 protein in the hippocampus of Alzheimer’s patients. The present data suggest that moderate overexpression of a phosphorylatable plasticity-related protein can enhance memory, while excessive overexpression may produce a “neuroplasticity burden” leading to degenerative and hypertrophic events culminating in memory dysfunction.
Footnotes
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↵1 Present address: Department of Psychology, Carleton University, B550 Loeb Building, 1125 Colonel By Dr., Ottawa, Ontario, Canada K1S 5B6.
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↵2 Corresponding authors.
↵2 E-mail matthew_holahan{at}carleton.ca; fax (613) 520-3667.
↵2 E-mail aryeh{at}northwestern.edu; fax (847) 491-3557.
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Article is online at http://www.learnmem.org/cgi/doi/10.1101/lm.581907
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- Received March 19, 2007.
- Accepted April 3, 2007.
- Copyright © 2007, Cold Spring Harbor Laboratory Press