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Flashcards in Graff 2012 Deck (25)
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1

when we have ____ is when dysregulation of Cdk5 occurs

p25

2

if ___ is cleaved incorrectly it makes ____

p35; p25

3

Cdk5 might have a part in what?

neurodegeneration

4

HDAC

an enzyme that removes the acetyl group from histone proteins on DNA, making the DNA less accessible to transcription factors

5

GFP

-green fluorescent protein
-used to visualize p25 cells

6

DAPI

-presents all of our cells in a section
-

7

Beta-Tubulin

housekeeping gene

8

what is the observed phenomenon?

Cognitive capacity in the neurodegenerated brain is constrained by an epigenetic block that is potentially reversible with HDACi treatment

9

hypothesis

Neurodegeneration (A) causes memory deficits (C) because (B) elevated HDAC2 mediates an epigenetic block.

10

predictions

1. A causes C: Neurodegeneration causes memory deficits.

2. Eliminating B should block A from causing C: Reducing the HDAC2-driven epigenetic block should prevent neurodegeneration from causing a memory deficit.

3. B itself should cause C: Elevating the HDAC2-driven epigenetic block causes memory deficits.

4. A should cause B: Neurodegeneration causes an elevated HDAC2-driven epigenetic block.

11

Prediction 1: neurodegeneration causes memory deficits

-Determine experiment.

-Technically, Figure 2h-j, although the authors already knew this before conducting these experiments.

12

prediction 2: Reducing the HDAC2-driven epigenetic block should prevent neurodegeneration from causing a memory deficit.

-block experiment
-figure 2h-j

13

prediction 3: Elevating the HDAC2-driven epigenetic block causes memory deficits.

-Mimic experiment.

-Not directly addressed, although the authors do “mimic” the conditions under which neurodegeneration occurs and show that these conditions produce an increase in HDAC2. They also explore the mechanism.

14

prediction 4: Neurodegeneration causes an elevated HDAC2-driven epigenetic block.

-measure experiment
-figure 1 and 4

15

HDAC2

-associated with reducing the histone acetylation of genes important for learning and memory

-causes a decrease in gene expression for genes important for memory and learning

16

reversing the build up of HDAC2 by shut-hairpin-RNA-mediated knockout (shHDAC2 CK-p25 ) unlocks what

-the repression of learning and memory genes
-reinstates structural and synaptic plasticity
-abolishes neurodegeneration- associated memory impairments

17

what has been associated with facilitating memory and learning

histone acetylation

18

acetylation diminishes what ?

-the electrostatic affinity between neighboring histones and the DNA, promoting a more open chromatin structure that allows for memory-related gene transcription

19

what are some pharmacological treatments used to increase histone acetylation

-non selective histone acetylation (HDAC) inhibitors

20

1. to investigate whether HDAC2 mediates cognitive deficits associated with neurodegeneration

-measurement
-methods use
-results

-measured HDAC2 abundance in CK-p25 mice

-immunohistochemistry and western blot analysis

-HDAC2 significantly increased in neuronal nuclei in hippocampal area CA1 in CK-p25 mice compared with control

21

2. determine thee functional consequences of elevated HDAC2

-measurement
-methods use
-results

-HDAC2 has been shown to associate with the promoter region of genes involved in memory they proposed that it is enriched at the genes following neurodegeneration

-focused on genes that had been demonstrated to be down regulated with Alzheimers disease

-measured genes implicated in learning and memory

-method: chromatin immunoprecipitation (ChIP)

-results: HDC2 is significantly enriched at these genes in the CK-p25 hippocampus

-HDAC2 high --> acetylation low --> RNA Pol II binding low --> mRNA gene expression low

-HDAC2 low ---> acetylation high --> RNA Pol II binding high --> gene expression high

22

T or F: HDAC2 mediates a local chromatin compaction of neuroplasticity genes, which decreases their expression and may contribute to cognitive decline during neurodegeneration

True

23

3. to test whether HDAC2 decreases expression and contributes to cognitive decline during degeneration

-method
-measurement
-results

-method: generated adeno-associated viral vectors carrying shRNAs directed against HDAC2 or scrambled control shRNAs. inject mice with virus using brain surgery

-measurement: injected into hippocampal area CA1 of CK-p25 and control mice and assessed HDAC2 levels 4 weeks later

-results: animals injected with an shRNA against HDAC2 (CK-p25, shHDAC2) showed reduced HDAC2 levels compared with CK-p25 animals injected with control scrambled shRNA (CK-p25, scr)

24

method use

tetracycline method

25

how memory formation occurs steps

1. glutamate receptors bind to AMPA
2. AMPA receptors open ion channels and let NA+ in
3. influx of sodium causes depolarization
4. depolarization gets rid of Mg plug
5. once Mg plug is off an influx of calcium occurs
6. calcium activates NMDA which causes a cascade of signals
7. signals cause LTP and synaptic plasticity
8. LTP methylates suppressors genes (decrease expression of the genes that suppress memory)
9. LTP unmethylates activator genes (increase the expression of the genes important for memory formation)
10. Unmethylation causes memory formation