Motor Neuron Disease Flashcards

1
Q

What are the 4 main types of MND?

A

Amyotrophic lateral sclerosis (ALS)
Progressive bulbar palsy (PBP)
Progressive muscular atrophy (PMA)
Primary lateral sclerosis (PLS)

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2
Q

Which MNs are affected in ALS?

A

Upper and lower

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3
Q

What are the symptoms of ALS?

A
Paralysis
Limb weakness
Difficulty keeping head upright
Difficulty with speech and swallowing
Breathing problems
Emotional lability
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4
Q

Name the 2 licensed drugs for ALS

A

Riluzole

Edaravone

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5
Q

What is riluzole and what is its effect?

A

Anti-glutamatergic

Slightly increases survival

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6
Q

What is edaravone and what is its effect?

A

Free radical scavenger - decreases oxi stress

Positive trial data with limited patient sample

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7
Q

Which other disease do some ALS patients also have?

A

FTD

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8
Q

Which type of MNs are most vulnerable to death in ALS?

A

MNs under voluntary control

MNs innervating fast twitch muscles

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9
Q

Name 4 genes that cause familial ALS

A

SOD1
TDP-43
FUS
C9orf72

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10
Q

What is the role of TDP-43?

A

RNA binding protein

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11
Q

What is the role of FUS?

A

RNA binding protein

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12
Q

What is the role of SOD1?

A

Superoxide dismutase - converts superoxide to water/hydrogen peroxide

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13
Q

What is the overall way in which SOD1 mutation causes ALS?

A

Toxic gain-of-function

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14
Q

What might the SOD1 toxic gain-of-function involve?

A

Increased superoxide

Axonal transport

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15
Q

Where are TDP-43 and FUS normally located?

A

Nucleus

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16
Q

Where are TDP-43 and FUS located in ALS and what is the effect of this?

A

Cytoplasm

Form cytoplasmic inclusions - depleted from nucleus

17
Q

What are the 2 proposed mechanisms for how mutant TDP-43 and FUS cause ALS?

A

Nuclear loss-of-function - transcription, splicing

Cytoplasmic gain-of-function - RNA transport

18
Q

What are the 3 proposed mechanisms for how hexanucleotide repeat expanded C9orf72 cause FTD-ALS?

A

C9orf72 loss-of-function
RNA toxicity - RNA foci formation
Protein toxicity - RAN translation in HRE - forms toxic DPRs - aggregation-prone

19
Q

What is thought to be the way in which mutant C9orf72 causes FTD-ALS?

A

RNA-mediated toxicity - gain-of-function

C9orf72 haploinsufficiency - loss-of-function

20
Q

What could cause the heterogeneity seen in ALS survival times?

A

Mutations in ALS-causing/susceptibility genes

Environmental factors

21
Q

Which environmental factors increase ALS risk?

A

Serious head trauma
Increased exercise
Heavy metal exposure
Low vitamin A diet

22
Q

Mutations in which gene link ALS to poor blood supply and what is the physiological role of this gene?

A

ANG

Angiogenesis

23
Q

Which pathogenic mechanisms are thought to be involved in ALS?

A
Protein aggregation
Oxi stress
Axonal transport defects
Mito dysfunction
Glutamate excitotoxicity
RNA processing
24
Q

How might protein aggregates lead to MN death in ALS?

A

Proteasome blockage
Autophagy overload
Depletion of essential cellular proteins - e.g. chaperones - increases misfolding - forms more aggregates
Toxicity leads to ER stress and axonal transport deficits

25
Which properties of MNs make them susceptible to excitotoxicity?
Low Ca2+ buffering capacity | High number of Ca2+-permeable AMPARs
26
What could be the effect of the deficits in anterograde and retrograde axonal transport seen in ALS model mice?
Key factors not taken to/from muscle
27
What is the evidence for the role of oxidative damage in ALS?
Increased oxidative damage in post-mortem ALS CNS tissue
28
How is mitochondrial function altered in ALS MNs?
Decreased ETC activity Decreased mito membrane potential Altered Ca2+ homeostasis
29
Where does mutant SOD1 localise to in ALS?
Spinal cord mitochondria
30
How might microglia be involved in ALS pathogenesis?
Become overactive when MNs die Release ROS - toxic Damage MNs - does not cause death
31
How are oligodendrocytes affected in SOD1 mutant mice and what is the effect of this?
Degenerate | Decreases support for MNs
32
What is the role of astrocytes in ALS pathogenesis?
Contribute to induction and propagation of MN death
33
What is the physiological role of astrocytes?
Modulate neuronal excitability - prevent excitotoxicity
34
Which patient characteristic prevents stratification in trials, making it more difficult to identify effective treatments?
Progression rate - varies between individuals
35
Name 2 potential ALS treatment types
ASOs | Stem cells
36
How might ASOs be used to treat ALS?
Prevent mutant gene expression - SOD1, C9orf72
37
How might stem cells be used to treat ALS?
Replace glial cells in spinal cord - increase MN support
38
Which mechanisms could future ALS treatments target?
``` Aggregation MN apoptosis Mitochondrial deficits Axonal transport Microglia ```