Nervous System Ageing LT2

Question 1

What causes ALS and what are the susceptible neurones?

Answer 1

TDP-43 inclusions

Upper and lower motor neurones

Question 2

What are the two descending spinal tracts and what do they control?

Answer 2

Lateral pathway = voluntary movement of distal muscle
Under direct cortical control

Ventromedial pathway = control of posture and locomation
Under brain stem control

Question 3

What phases can voluntary movement be divided into?

Answer 3

Planning
Initiation
Execution

Question 4

What is the role of sensory feedback?

Answer 4

Allows brain to correct for any deviation between the planned movement and actual movement

Question 5

What is Lou Gehig’s disease?

Answer 5

Aka amyotrophic lateral sclerosis (ALS) = motor neurone disease

Causes loss of muscle control but sensory information is INTACT

Question 6

What are the clinical signs of ALS?

Answer 6

Paralysis without loss of sensation of the upper limb

Accompanied by rapid wasting of muscle

Spasmodic rigidity of muscle results in permanent deformation of limbs

Speech and swallowing difficulties

Die due to respiratory issues = breathing nerves and muscles are affected

Question 7

What were the pathological/anatomical findings?

Answer 7

Symmetric sclerosis (harderining) of lateral columns in spinal cord

In grey matter, only small number of cells left with deformed and atrophied cells

Muscle atrophy = amyotrophy

Question 8

How are ALS clinical signs and pathological finding connected?

Answer 8

Grey matter motor nuclei are damage = weakness associated with muscular atrophy in body areas supplied by those cells

When white lateral column damage occurs = weakness associated with progressive contractures and spasticity

Question 9

When does ALS onset?

Answer 9

Adult-onset neurodegenerative disease = 45-60 y.o

Question 10

What genetic mutations cause ALS pathogenesis?

Answer 10

SOD1
Inclusion in sporadic ALS = TDP-43
Mutations in FUS

Question 11

How is ALS passed on?

Answer 11

90% appear as sporadic mutations
10% is due to familial history

Transmits DOMINANT fashion = one copy is enough to cause ALS in humans

Question 12

What type of mutation in SOD1 causes ALS?

Answer 12

Gain of function of the mutated protein causes aggregation

Not loss of enzymatic activity of SOD1

Question 13

Where are these SOD1 mutations found?

Answer 13

In multiple cell types that contribute to SOD1-mediated ALS

Question 14

Does neurone-specific expression of mutant SOD1 produce ALS-like phenotype?

Answer 14

No, neurone-specific expression of ALS-associated mutant human SOD1 may not be sufficient for development of the disease in mice

Mice expressing mutant SOD1 in all tissue developed ALS-like phenotype

Question 15

How did they get neurone-specific expression of mutant SOD1 in mice?

Answer 15

Used a neurofilament promoter = only expressed in neurofilaments

In combination with Cre/LoxP

Question 16

What were the 3 approaches to studying SOD1 mutations in difference cell types?

Answer 16

Try expressing mutation in only one type of cell

Express mutation in all cells and remove expression from one cell type at a time

Co-culture expt = reconstruct interaction between the two

Question 17

What are the different cell types SOD1 is found in, in the brain?

Answer 17

Motor neurones
Astrocytes
Microglia
Schwann cells

Question 18

What time in the progression does mutant SOD1 in motor neurones drive?

Answer 18

Early disease progression

Question 19

What role do motor neurones play in ALS?

Answer 19

Most likely, motor neurones are important for disease initiation

Question 20

What time in the progression does mutant SOD1 in microglia drive?

Answer 20

Late disease progression

We can see when the mutated SOD1 is removed from microglia in the late disease phase mice lived 75days longer

Question 21

What time in the progression does mutant SOD1 in astrocytes drive?

Answer 21

Late disease progression

Less severe difference in survival compared to microglia only 48 days instead of 75 in late phase

Question 22

How are induced pluripotent stem cells (iPSCs) made?

Answer 22

Study genes important for stem cell funciton
When 4 such genes were transfered into cells taken from the skin = reprogrammed into PSCs

These PSCs could develop into all cell types of an adult mouse = iPSC

Question 23

What causes ALS clinical hallmarks?

Answer 23

The death of motor neurones causes paralysis and muscle atrophy

Question 24

What was the difference between removing mutant SOD1 from motor neurones compared to microglia?

Answer 24

Removal of the SOD1 transgene from motor neurons was found to substantially delay but not halt the onset of disease.

While removal of the mutant SOD1 transgene from microglia was found to extend life span in the animals by prolonging the disease’s symptomatic phase

Question 25

How did they test whether the human spinal motor neurons produced from ESCs were useful for investigating disease processes?

Answer 25

Tested whether they were sensitive to the toxic effect of glial cells overexpressing a mutant SOD1 gene product

Question 26

What was seen when SOD1-mutant and WT glial cells were cocultured with transgenic human motor neurones?

Answer 26

In cultures containing SOD1G93A glia, there were less than half as many motor neurons (131± 53, n = 3) as in cultures containing nontransgenic control glia (269 ± 44, n = 3)
The deficit in motor neuron survival in cocultures with SOD1G93A glia became even more pronounced after 20 days.

A similar effect on survival of human ESC-derived motor neurons was observed when they were cultured for 20 days with media conditioned by SOD1G93A glia

Question 27

What causes the toxic effect of glia on motor neurones?

Answer 27

The action of the mutant SOD1 protein

NOT the overexpression of the SOD1 protein (large-scale protein aggregation)

Question 28

What does SOD1 mutation in Schwann cells do to ALS progression?

Answer 28

SLOWS disease progression

Question 29

What does SOD1 mutation in muscle and vasculature do to ALS progression?

Answer 29

No effect on disease

Vasculature is damaged early in ALS = leading to loss of tight junctions between ECs and microhemorrahges
But this may not be from mutant SOD1 in pericytes

Question 30

How does excitotoxicity contribute to SOD-1 mediated ALS?

Answer 30

Exocitotoxicity = hyperactivation of motor neurones

Resulting from failure to rapidly remove NT glutamate from synapse due to deficiency in glutamate transporter in neighbouring astrocytes

Question 31

How does ER stress contribute to SOD-1 mediated ALS?

Answer 31

Er stress = induced by abnormal interactions of mutant SOD1 with ER proteins

Question 32

How does proteasome inhibition contribute to SOD-1 mediated ALS?

Answer 32

Proteasome inhibition = due to overload of proteasome degradation pathway

Overloaded with ubiquitinated misfolded protein aggregates may damage astrocytes and motor neurones

Question 33

How does mitochodnrial dysfunction contribute to SOD-1 mediated ALS?

Answer 33

Provokes release of cytochrome c in motor neurones, which triggers apoptotic pathways

Astrocytes leads to nitroxidative stress; they are less susceptible to apoptosis compared to neurons

Question 34

How does toxic extracellular SOD1 mutation contribute to SOD-1 mediated ALS?***

Answer 34

Is secreted from motor neurones and astrocytes after interaction with components of neurosecretory vesicles

Question 35

How does superoxide production contribute to SOD-1 mediated ALS?

Answer 35

Produced from microglia or astrocytes = can damage neibouring motor neurones

Question 36

How does altered axonal transport contribute to SOD-1 mediated ALS?

Answer 36

Includes an increase in retrogradely transported stress-related proteins

Reported in mutant SOD1-expressing motor neurones

Question 37

How does synaptic vesicle defects contribute to SOD-1 mediated ALS?

Answer 37

Such as stalling and loss from distal synapse in vulnerable motor neurones is early event in ALS

Question 38

How does loss of tight junction proteins contribute to SOD-1 mediated ALS?

Answer 38

Results in distribution of blood-spinal cord barrier and occurrence of microhemorrhages within spinal cord well before disease onset

Question 39

Name a potential therapy to extend survival in ALS patients?

Answer 39

Silencing mutant SOD1 using RNAi to protect against neurodegeneration and extend survival of ALS model

Question 40

Explain how antisense oligonucleotides (ASOs) therapy for SOD1 in humans will help ALS?

Answer 40

It reduces SOD1 by binding to mRNA and preventing SOD1 translation into protein

It was found the removal of SOD1 WT didn’t have an adverse affect

Question 41

Explain how stimulation of neurogenesis in regions of injury may contirbute to restoring functions in humans with ALS?

Question 42

Explain how transplantation of glia precursor cells protect against ALS?