Lecture 5- Huntington's Disease Flashcards

1
Q

background of HD

A

monogenic disorder, autosomal dominant, genetic stutter, 10-20yrs progression

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2
Q

symptoms of HD

A

psychiatric (depression), cognitive deficits, movement disorder (chorea)

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3
Q

genetics of HD

A

CAG/glutamine repeat in huntingtin gene
- normal 10-30 CAGs
-HD >40 repeats, encodes more glutamines
brain regions- most toxic to cerebral cortex and striatum but also outside

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4
Q

brain regions affected

A

inner-cordate putamen (makes up striatum- part of basal ganglia)
outer- cerebral cortex

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5
Q

synpatopathy

A

disorder of synapses

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6
Q

circuitopathy

A

disorder of circuits

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7
Q

corticostriatal loop

A

striatum to cortex and back around

  • implicated in motor/cognitive function, movement, affective function (depression)
  • dysfunction of cells and death of neuronal population (disrupt loop)–>motor and cognitive dysfunction
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8
Q

pathological plasticity covers (2)

A

1- adult neurogenesis

2- synaptic plasticity

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9
Q

adult neurogenesis

A

birth of new neurons in certain regions of brain

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10
Q

synpatic plasticity

A

way in which neurons are wired, connections via synapses

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11
Q

what can pathological plasticity cause?

A

cellular dysfunction, cognitive and psychiatric symptoms

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12
Q

transgenic HD mice

A

R6/1 mice- similar brain circuits, 95% same genome, test movement/motion/cognition
express human exon 1 transgene encoding expanded polyglutamine

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13
Q

genetic construct validity

A

use animal model that has human mutation

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14
Q

face validity

A

show over time mice develop cognitive problems, affective signs etc just like humans

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15
Q

abnormal vocalisation

A

precedes motor onset in HD mice

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16
Q

touchscreen chambers

A

learn cognitive tasks and get rewarded, similar to human cognitive tasks
- translational implications to humans

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17
Q

disease onset and progression in HD mice

A

affective/cognitive abnormalities–>motor deficits–>decreased cortical and striatal volume–>neuronal death–>end-stage disease

18
Q

genetic contribution to HD

A

thought to be 100% genetic, but environmental factors

19
Q

environmental contribution to HD

A

modulate age of onset of disease
positive modulators- physical activity, stimulation, caloric restriction
negative modulators- obesogenic diet, sedentary lifestyle, high stress

20
Q

why is a delay in onset good>

A

would be a ‘cure’ since you just die of old age

21
Q

standard housing vs environmental enrichment

A

standard- normal bedding etc

EE- toys, opportunity for cognitive stimulation

22
Q

EE and activity levels

A

enhances activity levels

23
Q

EE and onset in HD mice

A

delays onset- by measuring loss of motor coordination (chorea)
- through physical activity and cognitive stimulation

24
Q

EE and cerebral cortex volume in HD mice

A

salvages loss of cerebral cortex volume in HD mice

- env reduced shrinkage of CC around striatum

25
EE and protein aggregation/clearance in HD mice
- small but significant change in size (measuring aggregates of abnormal protein)
26
Wexler study evidence for environmental modifiers in HD
analysed venezuelan kindreds- founder effect | - remaining variance in age of onset not explained by CAG repeat length
27
Trembath et al study evidence for environmental modifiers in HD
retrospective study of NZ and aus families | - passivity (reduced activity) risk factors, contributes to earlier age of HD onset
28
EE, neurogenesis and synaptic plasticity
experience dependent regulation | - enhances both neurogenesis and synaptic plasticity
29
brain target regions for HD gene expression
neocortex (frontal, parietal, occipital) hippocampus striatum
30
EE and cognitive deficits
EE delays onset of hippocampal dependent cognitive deficits in HD mice - delayed onset of dementia in HD
31
2 proteins- molecular mediators of synaptic plasticity
GluR1 and PSD95- important in forming memory and cognition
32
GluR1
protein level down in hippocampus
33
PSD95
protein level down in hippocampus | upregulated by enrichment
34
DARPP-32
dopamine and cAMP regulated neuronal phosphoprotein - protein levels affected in anterior cortex - protein rescued by EE in striatum
35
BDNF
brain derived neurotrophic factor - levels disrupted in non-enriched HD - rescued by EE in anterior cortex and hippocampus (model of depression and antidepressant action)
36
HD and stress
decreased neurogenesis, depression/cognitive deficits
37
SSRI
selective serotonin reuptake inhibitor- antidepressant | - rescues depression like behaviour in female HD mice
38
EE and SSRIs
increased neurogenesis, cognitive effects (antidepressant)
39
enhanced voluntary physical exercise
delays onset of short term spatial memory deficit | -reduces abnormal stress response
40
sexually dimorphic HPA axis dysfunction
female- stress levels decrease then increase post-stress induction male- stress levels progressively decrease post-stress induction
41
elevated stress hormone levels
accelerates cognitive decline
42
EE and adrenals
experience dependent adrenal dysfunction; EE can directly affect adrenals via epigenetic mechanism