Motor Neuron Disease Flashcards
What are the 4 main types of MND?
Amyotrophic lateral sclerosis (ALS)
Progressive bulbar palsy (PBP)
Progressive muscular atrophy (PMA)
Primary lateral sclerosis (PLS)
Which MNs are affected in ALS?
Upper and lower
What are the symptoms of ALS?
Paralysis Limb weakness Difficulty keeping head upright Difficulty with speech and swallowing Breathing problems Emotional lability
Name the 2 licensed drugs for ALS
Riluzole
Edaravone
What is riluzole and what is its effect?
Anti-glutamatergic
Slightly increases survival
What is edaravone and what is its effect?
Free radical scavenger - decreases oxi stress
Positive trial data with limited patient sample
Which other disease do some ALS patients also have?
FTD
Which type of MNs are most vulnerable to death in ALS?
MNs under voluntary control
MNs innervating fast twitch muscles
Name 4 genes that cause familial ALS
SOD1
TDP-43
FUS
C9orf72
What is the role of TDP-43?
RNA binding protein
What is the role of FUS?
RNA binding protein
What is the role of SOD1?
Superoxide dismutase - converts superoxide to water/hydrogen peroxide
What is the overall way in which SOD1 mutation causes ALS?
Toxic gain-of-function
What might the SOD1 toxic gain-of-function involve?
Increased superoxide
Axonal transport
Where are TDP-43 and FUS normally located?
Nucleus
Where are TDP-43 and FUS located in ALS and what is the effect of this?
Cytoplasm
Form cytoplasmic inclusions - depleted from nucleus
What are the 2 proposed mechanisms for how mutant TDP-43 and FUS cause ALS?
Nuclear loss-of-function - transcription, splicing
Cytoplasmic gain-of-function - RNA transport
What are the 3 proposed mechanisms for how hexanucleotide repeat expanded C9orf72 cause FTD-ALS?
C9orf72 loss-of-function
RNA toxicity - RNA foci formation
Protein toxicity - RAN translation in HRE - forms toxic DPRs - aggregation-prone
What is thought to be the way in which mutant C9orf72 causes FTD-ALS?
RNA-mediated toxicity - gain-of-function
C9orf72 haploinsufficiency - loss-of-function
What could cause the heterogeneity seen in ALS survival times?
Mutations in ALS-causing/susceptibility genes
Environmental factors
Which environmental factors increase ALS risk?
Serious head trauma
Increased exercise
Heavy metal exposure
Low vitamin A diet
Mutations in which gene link ALS to poor blood supply and what is the physiological role of this gene?
ANG
Angiogenesis
Which pathogenic mechanisms are thought to be involved in ALS?
Protein aggregation Oxi stress Axonal transport defects Mito dysfunction Glutamate excitotoxicity RNA processing
How might protein aggregates lead to MN death in ALS?
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