Transcription factors NF-kB, CREB and Egr-2 and their potential role in memory formation
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Date
2013-07-04
Authors
Pahlavan, Payam Samareh
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Abstract
Memory is subdivided into short- and long-term memory. The interaction between transcription factors (TF) and expressed genes are essential steps in memory formation. Some TFs that might be involved in memory formation include CREB, NF-kB and Egr-2. We hypothesized that there would be a difference in the expression levels of these TFs following learning in the Morris Water Maze (MWM). In study one, CD1 mice were categorized into two groups. Group 1 assigned as non-trained control group. Group 2 (experimental group) underwent 9 consecutive days of MWM training. In the second study, male C57BL/6 mice were categorized into four groups. Group 1 was a non-trained control group (allowed to swim randomly). Groups 2, 3, and 4 (experimental groups) had variations in their MWM training. Search strategies, escape latency, time spending in the target quadrant and number of attempts passing the missing platform, were measured. To evaluate the expression levels of TFs pre- versus post-learning, mice were sacrificed at the end of MWM. Hippocampi were separated and Western blot and immunohistochemical procedures were done. In study one, the escape latency decreased progressively toward the end of the acquisition phase in the trained group. The search pattern showed that the mice used primarily spatial strategies. Mice spent more time in the target quadrant during the retention phase. The number of passes over the missing platform peaked on the first day of the retention phase. NF-kB and CREB were expressed significantly higher in the control group versus the MWM trained mice (p = 0.0031 and p < 0.0001 respectively). There was no statistically significant difference in expression of Egr-2 between the two groups (p = 0.3092). In study two, Group 4 showed the highest and Group 1 the lowest levels of CREB expression. CREB and NF-kB were decreased following MWM training in study one. In study two CREB levels were highest in the Group 4 which had interval between the acquisition and retention phases. These differences could be due to multiphasic expression patterns and/or other experimental design issues. Further studies are warranted to examine time dependent differential expression of TFs in memory.
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Keywords
Transcription factors, CREB, NF-kB, Egr-2, Morris Water Maze, memory