Tuesday, 3 April 2012

Zebrafish : The Current and Future in Neuroscience

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Why this topic?

Because of this, click me!

Some videos here:


Video of zebrafish news:
"Zebrafish regenerate cells similar to ones used for human hearing"

Zebrafish news! Click to watch!

Video of spinal cord regeneration and response to fear stimulus in zebrafish:

http://www.youtube.com/embed/XCGWfR4Yk5g



Since when?

In the 1980s, the zebrafish was first established as a research subject by a scientist named George Streisinger. This fish was used because of various reasons, mainly being simple and easy to manipulate genetically. Since then, zebrafish embryo had been used to study the development of nervous system as the embryo were optically transparent. Later in the 1990s, developmental biology was studied using this organism, including mutation. The zebrafish genome sequencing began in the 2000s and are over 80% completed today, showing a similar collection of genes to other vertebrates.


Why choose Zebrafish?



- small, easy storage in large numbers
- simple husbandry
- optically transparent in their embryonic and larval forms
- rapid generation time
- external development
- cheaper to keep/cost effective
- genome has been sequenced thus a number of genetic tools are available
- uses a similar collection of genes to other vertebrates to build a nervous system
- similar to mammals in many structures and processes
- complements mice, rats, fruit fly research
- a relatively new subject to study on
- easily amenable to genetic manipulation
- examine cellular processes
- drug discovery

- the possibility to conduct high resolution in vivo imaging

∴ An Ideal Model Organism



Research for?



Zebrafish are used as models to study brain behaviour, neurogenesis, development, oncogenesis, and a variety of human diseases. Recently, zebrafish have been used in the study of neurodegenerative disorders. Compared to mammals, many structures and processes are similar in zebrafish such as the brain and spinal cord. The externally fertillized egg and transparent embryo made researches particularly easier. Many applicable attributes of the central nervous system (CNS) are shown within 1 day of development, making the study of neuroscience with these creatures more popular. These studies may even lead to drug development and discovery.

Methods of research?


Since most of the genome has been sequenced, a number of genetic tools are available for research. Many different methods are used in determination of various aims such as degenerative diseases, drug effects, fear response, and regeneration. The similarity between all researches is the use of microscopic live imaging of whole embryos or a developed zebrafish. To enable clear observation on the early development of the CNS; brain and spinal cord, dye is injected into the embryo. Studies of neural regeneration have been carried out in assorted CNS tissues such as retina, optic nerve, spinal cord, and brain nuclei. Images were collected and compiled every hour for 36 hours on the dyed target organ. As for degenerative diseases, transgenic zebrafish models were injected with drugs that can either activate the regenerative cells for regeneration or inhibit further impact caused by the diseases. A fear response test could be done before and after drug injection to differentiate the fish's reaction to the stimulus.

1. Injections

Injection into zebrafish embryos at the early stages of development.


2. Immunostaining and in situ labeling

Gene expression and protein visualization.


3. Transgenic technology

using Tol2 system



A. Cre-induced recombination.
B. MAZe transgenic system for the induction of protein expression in a spatial-temporal fashion.


4. Interfering with gene function

A. ATG morpholino action.
B. Zinc finger nuclease action.


5. Transplantation

A. The transplantation procedure.
B. The transplanted GFP-labeled cells from the transgenic embryo carrying gfap:gfp construct are shown in the forebrain of the donor embryo. The red staining corresponds to alpha-tubulin.


Disadvantages/Limitations?


Although many successful research has been done on the zebrafish, this organism still have its limitations. More advanced technologies are needed for detailed observations of sub-cellular structures and processes that are too complex which would in turn increase research costs. The zebrafish are new model organisms compared to rats and mice, behaviour-wise is insufficiently studied.

Future aspects?


With an increased understanding of the regeneration process and numerous development of brain diseases in zebrafish, these becomes potential for drug discovery in the future. Painless treatments and reduced side effects from existing drugs may also be assisted by these understandings. Thus, zebrafish are favourable, unique models that provides novel insights into neurodegenerative diseases.




Conclusion




References

Luca, R.M., and Gerlai, R. 2011. In search of optimal fear inducing stimuli: Differential behavioral responses to computer animated images in zebrafish, Behavioural Brain Research, 226(1), pp.66-76.

Fleisch, V.C., Fraser, B., and Allison, W.T. 2011. Investigating regeneration and functional integration of CNS neurons: Lessons from zebrafish genetics and other fish species, Biochimica et Biophysica Acta - Molecular Basis of Disease, 1812(3), pp.364-380.

Kabashi, E., Brustein, E., Campagne, N., and Drapeau, P. 2011. Zebrafish models for the functional genomics of neurogenetic disorders, Biochimica et Biophysica Acta - Molecular Basis of Disease, 1812(3), pp. 335-345.

Rinkwitz, S., Mourrain, P., and Becker, T.S. 2011. Zebrafish: An integrative system for neurogenomics and neurosciences, Progress in Neurobiology, 93(2), pp.231-243.

Sakowski, S.A., Lunn, J.S., Busta, A.S., Palmer, M., Dowling, J.J., and Feldman, E.L. 2012. A novel approach to study motor neurons from zebrafish embryos and larvae in culture, Journal of Neuroscience Methods, 205(2), pp.277-282.

Simmich, J., Staykov, E., and Scott, E. 2012. Zebrafish as an appealing model for optogenic studies, Progress in Brain Research, 196, pp.145-162.


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