Why do we use animal models in neuroscience research?
> A means to address a scientific question
In vivo vs in vitro: better understanding of the causes, mechanisms, pathways
- from molecule to mind
What is Charles Darwin’s ‘Tree of life’ (1837)?
> Illustrates the phylogenetic relationship
- how knowledge gained in a specific animal relates to others and humans
> Darwin’s idea: animals might be related to each other
What is the phylogenetic relationship?
Relationship between species
What does the phylogenetic tree of animals show?
Phylogenetic relationships can be remote
- e.g. humans are separated from insects by almost 500 million years
- yet, there is still a trace
- > we can learn about humans from insects
What is Darwin’s concept of homology, and homologous structures (1876)?
“The relative position or connection in homologous parts; they may differ to almost any extent in form and size, and yet remain connected together in the same invariable order.”
What are homologous genes/proteins?
Sequence identity between orthologous genes/proteins from different species
-> confirmation of Darwin’s hypothesis of homology
What is structural homology?
Different species have similar structures and structure positions
What are the 6 things we can learn from animal models?
Knowledge and understanding about the function of
1. A gene and its encoded proteins (including various protein isoforms)
- Gene-protein interaction
- Signalling pathway and how it works
- Formation/specification of cell types, tissues and organs
- Circuits and networks in the nervous system
- Genes and circuits in relation to disease
To gain knowledge and understanding from animal models, what do functional studies involve?
- Mutating, inactivating or over expressing a gene/protein
- Finding interacting/binding partners
- Screening for enhancers/suppressors of ‘disease gene/protein’
- Epistasis tests and manipulation of a signalling pathway
- who comes first and next - Targeted activation/inactivation of neural circuits
- Regulation and function of behaviour
What does epistasis refer to?
“Any relationship of nonadditive interaction between two or more genes in their combined effects on a phenotype”
To what extent (in vivo) functional studies are possible in animals and humans?
> Ethics committee approval and Home Office (UK) consent are mandatory requirements for work with vertebrates
> Only cell culture or non-invasive studies with written consent are possible regarding humans
What underlies insect and mammalian brain development?
Conserved genetic program that underlies the formation of an insect and mammalian brain
- even though they are different in size and composition
- some genes in a fly and a mouse show structural similarity, are expressed in similar ways, and seem to have similar functions
- > theme, architectural plan with similarities and dissimilarities
What is Saccharomyces cerevisiae?
Baker’s and brewer’s yeast
What is a yeast?
A eukaryotic cell
- all mammals are made of them
How has baker’s/brewer’s yeast been used scientifically?
To discover genes and their function in the regulation of the cell cycle/division - which is conserved across the animal kingdom
How is the YFP protein used in functional studies?
To highlight the cell body and nucleus
How did Couthouis et al. (2011) use Saccharomyces cerevisiae - yeast?
- TDP-43 and FUS proteins form aggregates and inhibit growth of yeast cultures
-> aggregate formation is associated to the viability of yeast
=> TDP-43 and FUS proteins build toxic aggregates - Researchers used yeast as an expression system to express several RNA binding proteins
- 3 readouts to screen for genes and proteins to form aggregates: cytoplasm diffuse, nucleus diffuse, cytoplasm aggregates - Cytotoxic effect of TAF15:
- increasing amount of the RNA binding protein TAF15 cause aggregate formation
=> TAF15: novel aggregate formation protein
- formation of pellets in Eppendorg tube
-> protein accumulates and precipitates - Human homologue of RNA binding proteinTAF15 forms aggregates
- found in post-mortem ALS patient tissue
=> Screen in yeast lead to the discovery of a novel disease-related gene in humans
What is amyotrophic lateral sclerosis (ALS)?
Progressive nervous system disease causing degeneration of upper and lower motor neurons (through brain, spinal cord and muscles)
- most common form of motor neuron disease
What is Caenorhabditis elegans and what are its characteristics?
The worm:
- simple anatomy
- 959 somatic nuclei
- 302 neurons
- small
- 250 progeny per generation
- easily cultivated
- eats bacteria
- grown on agar plates seeded bacteria
- rapid development (3-day life cycle)
What is a pedigree?
Tree of life starting at the top from one single cell and all derived cells
What did John Sulston receive a Nobel prize for?
Discovery of cell lineages and the clonal origin of cell types and tissues using C. elegans (worms)
What in the C. elegans (worm) makes it possible to study cell fate decisions and how they’re determined?
Invariant lineages that give rise to the animal
What characterises the C. elegans’ generation cycle?
> Short generation cycle
Worms generate lots of progeny
> Larval stages can be interrupted when there’s an overcrowding in the culture or wether there is a shortage of food
> At larval stages L1 to L2, the worm can go into dauer stage
What in the C. elegans makes it an ideal model organism to study the genetic basis of aging?
Worms have a short life cycle and don’t get very old
