5.3 Disorders of the Basal Ganglia: Huntington’s Disease Flashcards

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1
Q

Describe the mode of genetic inheritance of Huntington’s

A

Autosomal dominant (it is a hunter, after all…)

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2
Q

Chorea word origin

A

Khoros -> dancing in chorus -> dance-like

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3
Q

Describe physical symptoms of Huntington’s disease

A
  • Chorea
  • Loss of coordination/balance
  • Slurred speech
  • Dysphagia
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4
Q

Describe cognitive symptoms of Huntington’s disease

A
  • Forgetfulness
  • Difficulty making decisions
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5
Q

Describe emotional changes in Huntington’s disease

A
  • Hostility (HUNTington’s)
  • Disinterest in life
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6
Q

Describe the change in the Huntington gene that leads to Huntington’s disease. How does this affect the Huntington protein?

A
  • Lengthened CAG repeat in Huntington’s gene
  • Leads to increased length of Huntington protein upon translation
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7
Q

Which basal ganglia pathway is affected FIRST in Huntington’s disease (eventually, both are)

A

Indirect pathway initially.

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8
Q

Describe the pathophysiology of Huntington’s

A
  • Loss of medium spiny neurons from caudate (and, later, putamen).
  • Affects indirect pathway first
  • Cortical atrophy
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9
Q

On which arm of which chromosome is HTT (Huntingtin gene) located?

A

Short arm of chromosome 4 (otherwise known as 4p).

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10
Q

What is the normal number of CAG repeats found in the HTT gene?

A

26 or fewer

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11
Q

How many CAG repeats in the HTT gene are required for “HD-causing” alleles. What is the range for “at risk” vs full-penetrance

A
  • 36 or more is HD-casuing
  • 36-39 is at risk
  • 40+ is full penetrance
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12
Q

Do heterozygotic/homozygotic Huntington’s disease have different ages of onset?

A

No. They do naht.

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13
Q

What is the function of Huntingtin?

A

Regulates mRNA transcription.

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14
Q

How many CAG repeats on HTT for “intermediate” range?

A

27-35

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15
Q

Describe the cis-acting factor that effects Huntington’s disease severity (affect gene expression only in the same chromosomal allele)

A
  • Interrupted CAG repeat (where there is a CAA in the penultimate repeat); increased stability, more common
  • Uninterrupted; less stable, less common
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16
Q

The risk of the sibling of someone with >40 HTT CAG repeats or 36-39 repeats having the same (or greater) number of repeats is…

A

50%