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Neuroscience Midterm 2 > Huntington's Disease > Flashcards

Huntington's Disease Flashcards

1
Q

What is Huntington’s Disease?

A

It is a genetic, hereditary, progressive neurogenerative disorder caused by a defect in a gene on the short arm of chromosome 4.

Caused by a dominant gene that codes for a large brain protein called huntingtin.

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2
Q

How many people are at risk of having HD in Canada?

A

1 in 7,000 people.

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3
Q

How many people are at risk of inheriting HD in Canada?

A

1 in 5,500 people.

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4
Q

How many people are affected by HD in Canada (e.g. spouse, friends, relatives, etc.)?

A

1 in 1,000 people.

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5
Q

Are men or women more at risk of inheriting HD?

A

Both have an equal risk.

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6
Q

The onset of HD symptoms occur between what ages?

A

35-55

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7
Q

Juvenile HD accounts for what percentage of all HD cases?

A

10%

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8
Q

Is there a cure for HD?

A

No but there are treatments to reduce severity.

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9
Q

What are some HD management options?

A

Multidisciplinary caregiving.

Exercise has been shown to help rehabilitate cognitive symptoms of HD.

Physical, occupational, and speech therapy.

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10
Q

How can HD be detected?

A

There is a genetic test to see if a person carries the mutated Huntingtin gene.

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11
Q

What is Genetic Anticipation?

A

Process where severity of a disease in future generations is anticipated based on genetic testing.

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12
Q

How can HD be diagnosed?

A

Symptoms, family history, imaging, and genetic testing.

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13
Q

How does stress impact HD?

A

It can hasten the onset of the disease.

A positive test result can actually add to the damage of HD.

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14
Q

When do symptoms of HD appear?

A

Later adulthood.

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15
Q

Why is HD a progressive disease?

A

Symptoms begin very subtly and eventually progress to more pronounced involuntary movements (Hyperkinetic).

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16
Q

What are the early stages of HD?

A

Face, trunk, and limbs move involuntarily and rapidly.

Not too noticeable, can be disguised by patient fairly easily.

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17
Q

What occurs as HD progresses?

A

Muscles begin to contract briefly and rapidly.

Arms and other body parts suddenly jerk.

Movements become uncoordinated, and eventually the whole body is affected.

18
Q

What are the later stages of HD?

A

Cognitive changes become pronounced.

Irritability, excitability, impulse control issues.

Changes in interests.

Severe depression, dementia, etc.

Death usually occurs 13 to 15 years post onset of symptoms.

19
Q

What are the symptoms of HD?

A

Chorea
Cognitive difficulties, including dementia
Emotional difficulties (e.g. depression, apathy, irritability, personality disorders)

Eventually, the motor and intellectual deterioration become so severe that sufferers are incapable of feeding themselves, controlling their bowels, or recognizing their own children.

20
Q

What is Chorea?

A

Abnormal movements (involuntary movements, dystonia, and motor coordination).

21
Q

The Striatum contains groups of specialized neurons called what?

A

Medium Spiny Neurons (MSN).

They also contain GABA interneurons

22
Q

Medium Spiny Neurons are specialized GABAergic cells that represent what rate of the neurons in the human Striatum?

A

95%.

23
Q

What are the two types of Medium Spiny Neurons?

A

Direct (D1) and Indirect (D2)

24
Q

What do the direct MSN do?

A

Excite their output structures and promote associated behaviours.

25
Q

What do the indirect MSN do?

A

Inhibit output structures and associated behaviours.

26
Q

What is said to account for the disorders of movements in HD patients?

A

Damage to neurons in the Basal Ganglia - specifically the D2 MSN - and loss of its inhibitory OUTPUT to the thalamus.

27
Q

What is responsible for the dementia and personality changes associated with HD?

A

Cortical degeneration.

28
Q

Which parts of the Basal Ganglia are most affected by HD?

A

Caudate
Putamen
Globus Pallidus

29
Q

Which parts of the brain are affect as the disease progresses?

A

The Cerebral Cortex (shrinking and thinning).

30
Q

In the later stages of HD, how many MSN are lost?

A

Up to 95%.

31
Q

What can you find in HD-affected neurons?

A

Intranuclear Inclusion Bodies and Perinuclear Aggregates of Huntingtin.

These cause interference of normal cellular function and activate intrinsic apoptotic pathways.

32
Q

What are the primary neurotransmitters in the Basal Ganglia?

A

GABA and Acetylcholine (ACh).

33
Q

What causes HD?

A

A mutation.
A carrier of the HD gene will develop the disorder, as will half of their offspring.
It is a single dominant gene .

Mutated huntingtin gene contains an expanded CAG repeat coding for Polyglutamine in the huntingtin protein.

Normal CAG repeats are between 10-25. In HD patients they are above 36x.

The longer the repeat, the earlier the age of onset.

Over generations, the mutation seems to add additional CAG codons, and the disease presents itself earlier and earlier.

34
Q

Where can the Huntingtin protein be found?

A

It is widely expressed throughout the brain, but is less prevalent in the peripheral nervous system.

35
Q

What does the Huntingtin protein look like in HD patients?

A

HD patients have misfolded huntingtin proteins that aggregate together, particularly in the Dorsal Striatum (D2 MSN).

36
Q

What happens when the misfolded Huntingtin proteins aggregate?

A

It triggers neuronal degeneration.

37
Q

Cell death is strongly correlated with what?

A

Functional disability.

38
Q

Cell death is thought to occur how?

A

Via apoptotic pathways, with activation of caspases.

39
Q

Mutated Huntingtin genes are thought to activate and initiate what?

A

They are thought to activate caspase proteins and initiate intrinsic apoptotic pathways.

40
Q

What are Caspases?

A

They are a family of enzymes involved in programmed cell death.

11 or 12 confirmed caspases in humans.

Each of them function slightly differently but initiate apoptotic pathways.

They are the point of convergence between extrinsic and intrinsic apoptosis.

41
Q

What does the activation of caspases ensure?

A

It ensures that cellular components are degraded in a controlled manner, with minimal effect on surround tissues.

Neuroscience Midterm 2 (6 decks)

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