Exam 1: ALS Flashcards
Lateral corticospinal tract
3/4
cross MEDULLA
LIMBS
LATERAL alpha-MN
Ventral corticospinal tract
1/4 axons
axons don’t cross
Neck, should, trunk
MEDIAL alpha-MN
Upper motor neuron disturbances
spasticity, weakness, enhanced deep tendon reflexes
Lower motor neuron disturbances
fasciculations, wasting, weakness
Who? Inheritance?
mostly Caucasian men
90% sporadic
10% familial dominance pattern
ALS symptoms
Clumsy hand hoarse voice (dysarthria) shoulder dysfunction weak foot (drop foot) difficulty walking (spastic gait) exercise intolerance fasciculation respiratory insufficiency cognitive impairment
As ALS symptoms spread throughout the body
weigth loss, fatigue, exaggerated reflexes, decreased coordination
Bizarre affect, uncontrolled inappropriate crying and laughing, inappropriate responses
overlap with frontotemporal dementia
With progression
can’t walk, stand, eat, or breathe
relentless progression
50% die in 30 months symptom onset
20% survive 5-10 years
lack of sensory involvement
3 presentations of ALS
1) 70% limb onset
2) 25% bulbar onset- speech/swallowing, respiration, dysapnea
3) 5% trunk and/or respiratory onset
Typical pathological features: SOD1
SOD1 aggregates in spinal motor neurons (Familial)
TDP-43 redistribution to cytoplasmic inclusions in spinal motor neurons in sporadic ALS
3 types of ALS genes
1) alter proteostasis and protein quality control
2) disrupt RNA stability and function
3) disrupt cytoskeleton dynamics of MN
Theories and predictive factors of ALS
unknown
bets predictive factors: age and family hisotyr
unsubstantiated: viral infection and lyme disease
Inherited ALS: SOD1 mutation
autosomal dominant
free radical scavenging enzyme
mouse = hind limb weakness.
Inherited ALS: TAR DMP (TDP-43) and FUS
multifunctional proteins involved in gene expression transcription/translation/transport
Inherited ALS: OPTN
encodes optineurin
involved in regulation of NFkB
Inherited ALS: ALS2: Alisin mutation
rare, recessive
encodes alsin protein, involved in cycling G protein between GDP-GTP state. pathology not understood
Chromosome 9p21 locus
GGGCC repeats on C9ORF72.
normal <16 while ALS patients have up to 1600. Patients present with aggressive disease, cognitive impairments toxicity not understood
Mechanisms of Motor Neuron Death: Cu/Zn SOD1
mutations in SOD1 identified, loss of antioxidant thought to cuase injury by superoxide. SOD1 catalyzes conversion of superoxide to hydrogen peroxide and oxygen
SOD1 mice not rescued by wildtype SOD
SOD1 KO don’t have issue
Animal model DOES NOT support SOD1/free radical theory
mutant = toxic gain of function
Mechanisms of Motor Neuron Death: Glia Cells
inflammation from microglial in response to SOD1 mutations
C9orf72 mutations associate with microglia activation
SOD1 mutations in oligodendrites induces demyelination
mutations impair astrocytes in buffering glutamate, promote excitotoxicity
mutant SOD1 slows antero/retrograde transport, no transport of RNA model
PROINFLAMMATORY CYTOKINES IN MICROGLIA
Mechanisms of Motor Neuron Death: ER stress
ER stress from misfolded proteins inpeeds degrading and removing non functional proteins
disrupted ubiquitin-proteasome system and autophagy
Mechanisms of Motor Neuron Death: Apoptotic factors
DNA fragmentation and elevated Bax
strengthened by data showing SOD1 mutants induce apoptosis
SOD1 mice have elevated Bad and Bax and decreased bcl-2/Bcl-xL
If you overexpress BCL2, delay onset
SOD1 mice show caspase activation (proteases), inhibition prolongs SOD1 life span
Mechanisms of Motor Neuron Death: Intermediate filaments
neurofilament proteins form cytoskeleton, abnormal synthesis/accumulation
abnormal transport. Unclear if accumulation of NFs causes or is caused by blockage.
mRNA analysis shown reduced NF light mRNA
Mechanisms of Motor Neuron Death: Defects in axonal transport
SOD1 mice = slow axon transport
mutations in dynactin (need for retrograde transport)
Mechanisms of Motor Neuron Death: Excitotoxicity
40% sporadic ALS patients elevated CSF.
EAAT2 is reduced in 95% biopsies from ALS patients
Theory is aberrant splicing of EAAT2 in mRNA, making truncated proteins. Unclear since splices also found in normal tissue.
Mechanisms of Motor Neuron Death: Growth Factors
vascular endothelial cell growth factor (VEGF) controls growth of blood vessels
KO mice for VEGF = motor neuron disease.
Intracerebroventricular injection of VEGF slows disease
clinical trials anticipated
Mechanisms of Motor Neuron Death: Mitochondrial dysfunction
some version of SOD1 show vacuoles with damaged mitochondria.
not in all SOD1 versions
Creatine- enhances energy storage and slows progression in SOD1 mice. Failed in human clinical trials
Main point: LOTS wrong in ALS. List all you can
over excited aberrant RNA metabolism dysregulated vesicle transport mitochondrial dysfunction impaired DNA repair failure to clear glutamate (hyperexcited) axonopathy disrupted cytoskeleton bad quality control system NF accumulation
Treatment: Glutamate modulators
Riluzole: blocks voltage dependent Na+ channels, inhibits glutamate release, blocks amino acid receptors.
increase in survival, but no difference in end morality
Also no benefit in strength and neurological function
Treatment: Antioxidants
Edaravone: free radical scavenger
slowed symptom progression, no cure
Vitamin E also slow progression.
Treatment: Energy Metabolism
Creatine/phospjocreatine- intracellular transporter of ATP from site of synthesis to location of use, helps energy production in mitochondria, maintains ATP levels.
Survival improved in SOD1 mice, ineffective in human clinical trials.
Treatment: Antinflammatory Agents
Prostaglandins synthesized from arachidonic acid by COX2
induce release of glutamate from astrocytes- role in excitotoxicity
COX2 inhibitors helped neuronal survival in in vitro studies and SOD1 mice, failed human clinical trials
Treatment: Neurotrophins
BDNF/GDNF/CNTF tested in multiple clinical trials. Failed to show response, produced adverse side effects (anorexia, nausea)
IGF-1 produced mixed results
more trials underway with stem cells, viral vectors, siRNA techniques
Paper: Retrograde viral delivery of IGF-1 prolongs survival in mouse
GFP expression in lumber motor neurons
Disease onset/mortality delayed by delivery of trophic factors
AAV retrogradely transported from presynaptic to cell body/nuc
Results: IGF-1 treatment prolonged life of SOD1 mice, improved muscle performance, even when delivered after symptom onset. IGF-1 animals also maintained body weight and muscle mass longer
Paper: VEGF delivery with retrogradely transported lentivector prolongs survival in a mouse ALS model
pseduotyping-engineering alternative viral envelopes to maintain tropism.
Plasmids with envelope, packaging, and transfer gene (viral genome) are used to make non-replication competent virus. This paper used EIAV with Rabies envelope to produce integrating virus with retrograde transport capabilities.
EIAV-VEGF INJECTed into hindlimb results in elevated VEGF expression in spinal tissue- virus can induce VEGF in target tissue
point: RETROGRADE WORKS
delayed decrease in rotarod task in SOD1 mice
delayed disease onset
increased lifespan
Paper: Lentiviral silencing of SOD1 by RNA
siRNA construct for SOD1 delays onset of disease in SOD1 mice
Paper: AAV4-mediated expression IFG-1 and VEGF
AAV deliver IGF-1 or VEGF
ALS survive better when added.
prolonged survival/motor function in animals
