Genetic tools to study mice Flashcards
mesolimbic pathway
VTA to NAc
conditional knockout definition/characteristics
transgenic mouse in which the transgene is knocked out in specific tissue, at a specific developmental stage , or in response to an exogenous substance
When is a conditional knockout used?
To overcome a gross phenotype in global gene knock out
What happens when VGLUT2 is removed from the VTA cells?
- In general: depletion of VGLUT2-mediated glutamatergic signalling
- no anxiety phenotype
- no motordeficiencies
- severly blunted response to amphetamine (they don’t move as much as the control mice on amphs)
- altered reward consumption and reward-associated memory
- findings indicate functional role for VGLUT2 in the reward system
- may be of relevance for addictive-like behaviour
Halorodhopsin
NpHR; from archaea
- activated by yellow light
- opens CL channels (inhibitory; Cl in) / ion pump
- turns cells OFF
Next generation technique
DelFlp mice containing 3 loxP sites and Flp sites, which are recognised by DelFlp
Effects of … on dopamine release
- Amphetamines
- Cocaine
- Nicotine
- Ethanol
amphetamines: up in accumbens
cocaine: up in acccumbens
nicotine: up in accumbens and less in caudate
ethanol: up in accumbens, even though not primary target
Characteristics of loxP sites
34 pb sequence:
two inverted 13bp repeats surrounding 8bp core
nigrostriatal pathway
substantia nigra to dorsolateral striatum (upper part of striatum); part of the basal ganglia
Challenges with optogenetics
- gene must be introduced into target tissue (you have to inject the virus to the right sight)
- volume of tissue activated is limited by intensity of light delivered by the fiber (light cannot travel that long and if too intense, it kills the cells)
- overexpression of ChR2 may lead to toxicity and loss of membrane integrity
Shortcomings/Cavets of the CreLoxP-system
- “leacky” Cre, i.e. expressed in more places than the endogenous gene (when the protein/promoter is not specific enough)
- transgenic Cre lines (which are easier to make) are randomly inserted -.> Cre is somewhere in the genome
- not very efficient promoter –> only low expression in cells of intrest
- knock-in cre lines: insertion into endogenous locus, which could lead to a disrupted reading frame
Mouse models currently available for genetic research
- different cancer types, diabetes, obesity, and blindness
- Huntington’s, Parkinson’s and Alzheimer’s disease
- anxiety, aggressive behaviour, alcoholism, and drug addition
How to identify glutamergic neurons
via vesicular glutamate transporters VGLUT1,2, and 3
mesocortical pathway
VTA to PFC
Channelrodhopsin
ChR; from an algea
- activated by blue light
- opens channels (excitatory; K out, Na in)
- turns cells ON
