The Role of RGS14 in Learning, Memory, and Synaptic Plasticity Público

Lee, Sarah Emerson (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/sb3979135?locale=es
Published

Abstract

The hippocampus is crucial for converting new experiences into long-
term memories following initial learning. Learning and memory are closely
linked to synaptic plasticity, which involves altering the strength of connections
between of neurons especially within the dentate gyrus (DG)-CA3-CA1
trisynaptic circuit of the hippocampus. Conspicuously absent from this circuit
is the intervening CA2 whose existence as a distinct region has been subject
to debate. The CA2 only recently been implicated in learning and memory.
CA2 neurons have a striking lack of synaptic long-term potentiation (LTP).
RGS14 is differentially expressed during postnatal development and is highly
enriched in CA2 pyramidal neurons. RGS14 is critically important for
suppressing synaptic plasticity in these cells and hippocampal learning and
memory. RGS14 is an unusual scaffolding protein that integrates G protein
and MAP kinase signaling pathways making it well positioned to suppress
plasticity in CA2 neurons. Supporting this idea, we find that deletion of exons
2-7 of the RGS14 gene yields mice that lack RGS14 (RGS14-KO) that also
express robust LTP following high frequency stimulation of Schaffer collateral
synapses, but with no impact on synaptic plasticity in CA1 neurons. When
tested behaviorally, RGS14-KO mice exhibited marked enhancement in the
acquisition of spatial learning and of object recognition memory compared with
their wild type littermates, but showed no differences in their performance on
tests of non-hippocampal-dependent behaviors. These results demonstrate
that RGS14 is a key regulator of signaling pathways linking synaptic plasticity
in CA2 pyramidal neurons to hippocampal-based learning and memory, and
RGS14 may serve as a memory filter that could be a pharmacological target to
provide general cognitive enhancement in patients with neurodegenerative
disorders.

Table of Contents

Table of Contents

CHAPTER 1: Introduction

1

1.1 Learning and Memory

2

1.2 The role of the Hippocampus in Memory

2

1.3 Neuroanatomy and Circuitry of the Hippocampus

5

1.4 The hippocampus in Human Disease

8

1.5 Cellular and Molecular Mechanisms of Memory hippocampal based memory

11

1.6 G protein Coupled Receptors

20

1.7 G Protein Coupled Receptor Signal Transduction

21

1.8 The Regulators of G Protein Signaling

23

1.9 Structure and interactions of RGS14

24

1.10 Objective of this dissertation

27

CHAPTER 2: Differential Expression of RGS14 during postnatal mouse brain development

29

2.1 Introduction

30

2.2 Materials and Methods

32

2.2.1 Plasmids and Cell lysates

32

2.2.2 Antibodies

33

2.2.3 Preparation of mouse brain lysates

33

2.2.4 Western Blot Analysis

34

2.2.5 Immunohistochemistry

34

2.2.6 Electron Microscopy

35

2.3 Results

36

2.3.1 RGS14 Monoclonal Antibody Characterization

33

2.3.2 Specific antibody for RGS14 protein

39

2.3.3 RGS14 antibody staining in RGS14-KO mice

39

2.3.4 Temporal Expression of RGS14 during postnatal brain development

42

2.3.5 Regional expression ofRGS14 in the developing mouse brain

44

2.3.6 RGS14 Protein Expression in Adult Mouse Brain

47

2.4 Discussion

53

CHAPTER 3: RGS14 is a natural suppressor of Learning, Memory, and Synaptic Plasticity

55

3.1 Introduction

57

3.2 Materials and Methods

58

3.2.1 Generation, genotyping, and RT-PCR of RGS14-KO mutant mice

58

3.2.3 Hippocampal Slice Preparation

59

3.2.4 Whole-cell patch recordings

59

3.2.5 Field potential recordings

60

3.2.6 Novel-object recognition

61

3.2.7 Morris water maze

61

3.2.8 Locomotor Activity

62

3.2.9 Startle Response

62

3.2.10 Elevated-Plus Maze Test

64

3.3 Results

65

3.3.1 Generation of an RGS14 Knock-out Mouse Model

65

3.3.2 Determining the function of RGS14 in synaptic activity

68

3.3.3 LTP in CA2 is blocked by MEK inhibition

70

3.3.4 RGS14-KO mice exhibit enhanced learning and memory

74

3.3.5 RGS14-KO mouse performance in non-hippocampus dependent tasks

78

3.4 Discussion

82

CHAPTER 4: Seizure susceptibility and extinction of learning in RGS14-KO Mice

85

4.1 Introduction

86

4.2 Materials and Methods.

88

4.2.1 Pilocarpine-induced seizures

88

4.2.2 Immunohistochemistry

88

4.2.3 Morris water maze

89

4.2.4 HeLa cells expressing EGFP-RGS14 Lentivirus

90

4.3 Results

91

4.3.1 RGS14-KO Mice are resistant to Pilocarpine induced seizures

91

4.3.2 Reversal and Extinction in the Morris water maze

95

4.3.3 Lentivirus expression of RGS14

95

4.4 Discussion

100

4.4.1 Pilocarpine induced seizure resistance in RGS14-KO mice

100

4.4.2 Extinction and Reversal in Morris water maze

101

4.4.3 Lentivirus vector expression of RGS14

102

CHAPTER 5: Conclusion

104

5.1 Roles for RGS14 during postnatal development

105

5.2 RGS14 is important for the acquisition of hippocampal-based spatial learning and object memory

106

5.3 RGS14 is a natural suppressor of synaptic plasticity in CA2 neurons

107

5.4 Possible mechanistic roles for RGS14 and its binding partners in synaptic plasticity.

110

5.5 Future Studies

116

5.6 Pharmacological Relevance

118

5.7 Summary

119

REFERENCES

121

Document Outline
  • Circulation documents
    • Table of Contents
    • List of Figures and Tables
  • Sarah Lee Thesis FINAL

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