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Molecular and genetic determinants of the NMDA receptor for superior learning and memory functions.

Jacobs S, Cui Z, Feng R, Wang H, Wang D, Tsien JZ - PLoS ONE (2014)

Bottom Line: The opening-duration of the NMDA receptors implements Hebb's synaptic coincidence-detection and is long thought to be the rate-limiting factor underlying superior memory.Surprisingly, we found that the voltage-gated channel opening-durations through either GluN2A or GluN2B are sufficient and their temporal differences are marginal.In contrast, the C-terminal intracellular domain of the GluN2B subunit is necessary and sufficient for superior performances in long-term novel object recognition and cued fear memories and superior flexibility in fear extinction.

View Article: PubMed Central - PubMed

Affiliation: Brain and Behavior Discovery Institute and Department of Neurology, Medical College of Georgia at Georgia Regents University, Augusta, Georgia, United States of America.

ABSTRACT
The opening-duration of the NMDA receptors implements Hebb's synaptic coincidence-detection and is long thought to be the rate-limiting factor underlying superior memory. Here, we investigate the molecular and genetic determinants of the NMDA receptors by testing the "synaptic coincidence-detection time-duration" hypothesis vs. "GluN2B intracellular signaling domain" hypothesis. Accordingly, we generated a series of GluN2A, GluN2B, and GluN2D chimeric subunit transgenic mice in which C-terminal intracellular domains were systematically swapped and overexpressed in the forebrain excitatory neurons. The data presented in the present study supports the second hypothesis, the "GluN2B intracellular signaling domain" hypothesis. Surprisingly, we found that the voltage-gated channel opening-durations through either GluN2A or GluN2B are sufficient and their temporal differences are marginal. In contrast, the C-terminal intracellular domain of the GluN2B subunit is necessary and sufficient for superior performances in long-term novel object recognition and cued fear memories and superior flexibility in fear extinction. Intriguingly, memory enhancement correlates with enhanced long-term potentiation in the 10-100 Hz range while requiring intact long-term depression capacity at the 1-5 Hz range.

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Related in: MedlinePlus

Constructs and basic behavioral assays of the GluN2 chimeric mice.(A) Illustration of the constructs used to create the GluN2A2B(CTR), GluN2B2A(CTR), and GluN2D2B(CTR) chimeric subunits. (B) A point mutation was made on the cloning vector to induce an Aat II cutting sites to link the N-terminal and membrane domain to the C-terminal domain. After successfully joining the domains, the point mutation was restored to the original sequence. The arrow indicates the fusion position located in trans-membrane domain. (C) In situ hybridization of the transgene expression in the wild-type mice (Wt), the Tg-GluN2A2B(CT) mice, the Tg-GluN2B2A(CT) mice and the Tg-GluN2D2B(CT) mice using SV-40 probes with a schematic of the receptor subunit expressed in the excitatory neurons. (D) No differences were found in the average adult body weight of the wild-type mice, the Tg-GluN2A2B(CT), Tg-GluN2B2A(CT), and Tg-GluN2D2B(CT)mice. (E) The chimeric transgenic mice spent similar amounts of time as the wild-type mice in the center verses the periphery of the open field arena. (F) The chimeric transgenic mice and the wild-type mice showed similar locomotion in the open field. (G) The Tg-GluN2A2B(CT), Tg-GluN2B2A(CT) and Tg-GluN2D2B(CT) mice spent similar amounts of time in the closed arms and the open arms of the elevated plus maze as the wild-type mice.
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pone-0111865-g001: Constructs and basic behavioral assays of the GluN2 chimeric mice.(A) Illustration of the constructs used to create the GluN2A2B(CTR), GluN2B2A(CTR), and GluN2D2B(CTR) chimeric subunits. (B) A point mutation was made on the cloning vector to induce an Aat II cutting sites to link the N-terminal and membrane domain to the C-terminal domain. After successfully joining the domains, the point mutation was restored to the original sequence. The arrow indicates the fusion position located in trans-membrane domain. (C) In situ hybridization of the transgene expression in the wild-type mice (Wt), the Tg-GluN2A2B(CT) mice, the Tg-GluN2B2A(CT) mice and the Tg-GluN2D2B(CT) mice using SV-40 probes with a schematic of the receptor subunit expressed in the excitatory neurons. (D) No differences were found in the average adult body weight of the wild-type mice, the Tg-GluN2A2B(CT), Tg-GluN2B2A(CT), and Tg-GluN2D2B(CT)mice. (E) The chimeric transgenic mice spent similar amounts of time as the wild-type mice in the center verses the periphery of the open field arena. (F) The chimeric transgenic mice and the wild-type mice showed similar locomotion in the open field. (G) The Tg-GluN2A2B(CT), Tg-GluN2B2A(CT) and Tg-GluN2D2B(CT) mice spent similar amounts of time in the closed arms and the open arms of the elevated plus maze as the wild-type mice.

Mentions: To investigate the potentially distinct roles of the C-terminal domains vs. the N-terminal and membrane domains in GluN2 subunits in mediating memory enhancement, we created constructs encoding chimeric receptors based on GluN2B and GluN2A but with their respective CTDs replaced (denoted as CTR) with each other's (GluN2B2A(CTR) and GluN2A2B(CTR), respectively. We have created three new chimeric GluN2 transgenic mouse lines. We used the same ╬▒CaMKII promoter for driving transgene expression in forebrain excitatory neurons as we did for producing the GluN2B [16] and GluN2A transgenic mice [23]. In the first transgenic line, termed Tg-GluN2B2A(CT) chimeric transgenic mice, the C-terminal domain of the GluN2B subunit has been swapped for the counterpart C-terminal domain of the GluN2A and overexpressed in the forebrain excitatory neurons (Figure 1A). This effectively pairs the opening duration of the GluN2B subunit with the signaling domain of the GluN2A subunit. In the second transgenic line, termed Tg-GluN2A2B(CT), the C-terminal domain of the GluN2A subunit has been swapped for the counterpart C-terminal domain of the GluN2B (Figure 1A). This chimeric subunit possesses the GluN2A opening duration but with the signaling domain from the GluN2B subunit. Additionally, to investigate the requirement of the Mg2+ dependent synaptic coincidence-detection function for producing GluN2B-mediated intracellular signaling, we created a third transgenic mouse line, namely, Tg-GluN2D2B(CT) mice, in which the C-terminal domain of the GluN2B subunit has been fused to the N-terminal and membrane domain of the GluN2D subunit (which is less Mg2+-dependent) denoted as GluN2D2B(CTR) (Figure 1A).


Molecular and genetic determinants of the NMDA receptor for superior learning and memory functions.

Jacobs S, Cui Z, Feng R, Wang H, Wang D, Tsien JZ - PLoS ONE (2014)

Constructs and basic behavioral assays of the GluN2 chimeric mice.(A) Illustration of the constructs used to create the GluN2A2B(CTR), GluN2B2A(CTR), and GluN2D2B(CTR) chimeric subunits. (B) A point mutation was made on the cloning vector to induce an Aat II cutting sites to link the N-terminal and membrane domain to the C-terminal domain. After successfully joining the domains, the point mutation was restored to the original sequence. The arrow indicates the fusion position located in trans-membrane domain. (C) In situ hybridization of the transgene expression in the wild-type mice (Wt), the Tg-GluN2A2B(CT) mice, the Tg-GluN2B2A(CT) mice and the Tg-GluN2D2B(CT) mice using SV-40 probes with a schematic of the receptor subunit expressed in the excitatory neurons. (D) No differences were found in the average adult body weight of the wild-type mice, the Tg-GluN2A2B(CT), Tg-GluN2B2A(CT), and Tg-GluN2D2B(CT)mice. (E) The chimeric transgenic mice spent similar amounts of time as the wild-type mice in the center verses the periphery of the open field arena. (F) The chimeric transgenic mice and the wild-type mice showed similar locomotion in the open field. (G) The Tg-GluN2A2B(CT), Tg-GluN2B2A(CT) and Tg-GluN2D2B(CT) mice spent similar amounts of time in the closed arms and the open arms of the elevated plus maze as the wild-type mice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216132&req=5

pone-0111865-g001: Constructs and basic behavioral assays of the GluN2 chimeric mice.(A) Illustration of the constructs used to create the GluN2A2B(CTR), GluN2B2A(CTR), and GluN2D2B(CTR) chimeric subunits. (B) A point mutation was made on the cloning vector to induce an Aat II cutting sites to link the N-terminal and membrane domain to the C-terminal domain. After successfully joining the domains, the point mutation was restored to the original sequence. The arrow indicates the fusion position located in trans-membrane domain. (C) In situ hybridization of the transgene expression in the wild-type mice (Wt), the Tg-GluN2A2B(CT) mice, the Tg-GluN2B2A(CT) mice and the Tg-GluN2D2B(CT) mice using SV-40 probes with a schematic of the receptor subunit expressed in the excitatory neurons. (D) No differences were found in the average adult body weight of the wild-type mice, the Tg-GluN2A2B(CT), Tg-GluN2B2A(CT), and Tg-GluN2D2B(CT)mice. (E) The chimeric transgenic mice spent similar amounts of time as the wild-type mice in the center verses the periphery of the open field arena. (F) The chimeric transgenic mice and the wild-type mice showed similar locomotion in the open field. (G) The Tg-GluN2A2B(CT), Tg-GluN2B2A(CT) and Tg-GluN2D2B(CT) mice spent similar amounts of time in the closed arms and the open arms of the elevated plus maze as the wild-type mice.
Mentions: To investigate the potentially distinct roles of the C-terminal domains vs. the N-terminal and membrane domains in GluN2 subunits in mediating memory enhancement, we created constructs encoding chimeric receptors based on GluN2B and GluN2A but with their respective CTDs replaced (denoted as CTR) with each other's (GluN2B2A(CTR) and GluN2A2B(CTR), respectively. We have created three new chimeric GluN2 transgenic mouse lines. We used the same ╬▒CaMKII promoter for driving transgene expression in forebrain excitatory neurons as we did for producing the GluN2B [16] and GluN2A transgenic mice [23]. In the first transgenic line, termed Tg-GluN2B2A(CT) chimeric transgenic mice, the C-terminal domain of the GluN2B subunit has been swapped for the counterpart C-terminal domain of the GluN2A and overexpressed in the forebrain excitatory neurons (Figure 1A). This effectively pairs the opening duration of the GluN2B subunit with the signaling domain of the GluN2A subunit. In the second transgenic line, termed Tg-GluN2A2B(CT), the C-terminal domain of the GluN2A subunit has been swapped for the counterpart C-terminal domain of the GluN2B (Figure 1A). This chimeric subunit possesses the GluN2A opening duration but with the signaling domain from the GluN2B subunit. Additionally, to investigate the requirement of the Mg2+ dependent synaptic coincidence-detection function for producing GluN2B-mediated intracellular signaling, we created a third transgenic mouse line, namely, Tg-GluN2D2B(CT) mice, in which the C-terminal domain of the GluN2B subunit has been fused to the N-terminal and membrane domain of the GluN2D subunit (which is less Mg2+-dependent) denoted as GluN2D2B(CTR) (Figure 1A).

Bottom Line: The opening-duration of the NMDA receptors implements Hebb's synaptic coincidence-detection and is long thought to be the rate-limiting factor underlying superior memory.Surprisingly, we found that the voltage-gated channel opening-durations through either GluN2A or GluN2B are sufficient and their temporal differences are marginal.In contrast, the C-terminal intracellular domain of the GluN2B subunit is necessary and sufficient for superior performances in long-term novel object recognition and cued fear memories and superior flexibility in fear extinction.

View Article: PubMed Central - PubMed

Affiliation: Brain and Behavior Discovery Institute and Department of Neurology, Medical College of Georgia at Georgia Regents University, Augusta, Georgia, United States of America.

ABSTRACT
The opening-duration of the NMDA receptors implements Hebb's synaptic coincidence-detection and is long thought to be the rate-limiting factor underlying superior memory. Here, we investigate the molecular and genetic determinants of the NMDA receptors by testing the "synaptic coincidence-detection time-duration" hypothesis vs. "GluN2B intracellular signaling domain" hypothesis. Accordingly, we generated a series of GluN2A, GluN2B, and GluN2D chimeric subunit transgenic mice in which C-terminal intracellular domains were systematically swapped and overexpressed in the forebrain excitatory neurons. The data presented in the present study supports the second hypothesis, the "GluN2B intracellular signaling domain" hypothesis. Surprisingly, we found that the voltage-gated channel opening-durations through either GluN2A or GluN2B are sufficient and their temporal differences are marginal. In contrast, the C-terminal intracellular domain of the GluN2B subunit is necessary and sufficient for superior performances in long-term novel object recognition and cued fear memories and superior flexibility in fear extinction. Intriguingly, memory enhancement correlates with enhanced long-term potentiation in the 10-100 Hz range while requiring intact long-term depression capacity at the 1-5 Hz range.

Show MeSH
Related in: MedlinePlus