B.20 Mouse Models Flashcards
Components Of Transgenic Rodent Models
2 main possible strategies
- loss of function
- gain of function
This means:
-mice contain additional artificially introduce genetic material
OR
-intergrated DNA disrupts another GENE (knock out model)
- > DNA is introduced at embryonic stage to ensure its expression throughout all cells of a desired type)
- usually insertion of human gene to observe expression of human protein
Components
*Promoter - drives expression
*ATG start Codon- drives translation
*gene of interest
*stop codon- stops translation
*enhancer sequence - increases transcription levels
PolyA - stabilises, propper translation and nuclear export of mRNA
Promoters
- help control expression stage and where it is expressed
- different promotors for postnatal expression for example
Phenotypes- HD
-loss of motor control
-behavioural and cognitive symptoms
-emotional issues
-Short Term memory deficits
-degenerative
hyperactive basal ganglia circuit
-inhibition of thalamus
Genetic Cause - HD
- autosomal dominant disorder
- HTT (expansion in Huntingtin gene) gene = cause
Mouse Models -HD 1
- Overexpression of Exon1/2
-R6/2 mice
-phenotype: crossed hindlimbs and motor dysfunction on rotor rod, striatum degenerated, many characteristics of human HD
Con: artefacts might be caused as additional genetic material is introduced that does not occur in HD
-die young and show pathology fast (not like human HD)
Mouse Model - HD 2
- Knock in Mice -insert human CAG mutation into mouse HTT (expansion)
- CAG150 mice
- phenotype: motordeficits later than R6/2 mice, normal life span, probably more genetic likeness to human HD
Mouse Model - HD 3
- Whole Chromosome insertion -> entire human WT HD
- phenotype: hindlimb paralysis, HD like appearance
- accumulation of human hit protein
Phenotype ALS/ FTLD
- spectrum
-motor dysfunction
-motor neuron degeneration
-Paralysis
-cognition unimpaired
Genetic Risk Factors:
SOD1 (Familiar), FUS and others
ALS/ FTLD - SOD1
- transgenic SOD1 mice
- loss of motor neurons
- more stationary than WT mice
- inclusions in spinal cord
- abnormal skeletal muscles
- > model helped understand: protein aggregation, cytoskeletal abnormalities, non neuronal cell types involved i.e inflammation interactions with microglia and astrocytes)
ALS/ FTLD - TDP43
KEY PROTEIN
- Over-expression of TARDBP (mutant TDP43)
- targeting hind brain by using prion promotor
- ALS type features
- fewer motor neurons
- abnormal skeletal muscles
- loss of hindlimb motor control
- Loss of TDP43 from nuclei
- Some FTLD features like accumulation of aggregates in cortex with age
Over-expression of WT TARDBP:
- similar features
- dragging of hindlimbs
Knock out of TDP43:
- less sever outcome than other two models
- loss of motor neurons
FTLD -TAU models
MORE DEVELOPED FIELD
- > disease phenotype achieved when over expressing any of the mutants
- formation of NFT, neuronal loss, cognitive impairment, hyper phosphorylation
Phenotype - AD
- memory loss
- Synaptic dysfunction
- Inflammation (neuro)
- Plaques/ Tangles
Genetic Causes/ Risk Factors - AD
- APP, APoE and others
- APP first found to cause AD
Mouse Models - AD
APP Transgenic:
-over expression or knock in mutant human APP
->in Swedish mutation mouse looks like WT, Plaques in cortex and hippocampus, no motor impairment, features of neural inflammation
HOWEVER: no tangle formation, no significant neurodegeneration, no TAU changes
Presenilin Transgenic mice:
-exacerbates the APP/Tau transgenic phenotype
-no memory deficits, no tau changes and no neuronal loss
=MAJOR deficit as neuronal major symptom of AD
Rat Model AD
- over expression of APP and PS1
> plaques and tangles present
impaired memory
Neurodegeneration prominent
? why rats and not mice?
-possibly life span or more susceptible to changes
