This document discusses research on zebrafish and their use as a model organism for studying heart disease. It provides background on zebrafish, noting their native habitat in South Asia and use in home aquariums as well as medical research. Zebrafish hearts share similarities with human hearts in structure and function. The summary describes how zebrafish are well-suited for genetic studies of cardiovascular development and disease due to external fertilization, transparent embryos, and ability to survive without circulation. It gives an example of how studying a zebrafish mutation helped researchers understand a genetic cause of human heart disease.

1. RESEARCHES ON ZEBRA FISH
By SREEREMYA.S, M.phil
Lecturer, Dept.Of Biotechnology
Mercy College,Palakkad

2. Zebra fish

3. WELFARE OF ZEBRA FISH
• This report aims to improve the welfare of zebrafish by:
• o facilitating understanding of zebrafish behaviour and thus a better
appreciation of their requirements;
• o highlighting current potential welfare and ethical concerns
relating to the breeding, supply, housing and care of zebrafish;
• o arriving, where possible, at consensus based on available
evidence and sound scientific argument for appropriate
environmental and care conditions for keeping zebrafish in the
laboratory environment;
• o providing recommendations for improving health, welfare and
egg quality, for reducing the potential for stress and suffering, and
for reducing the number of animals used;
• o in areas where current knowledge is sparse or inconclusive,
stimulating discussion and research to identify ‘good practice’.

4. Natural geographic range and habitat
• The exact current natural geographic range of the zebrafish is still far from
clear. Engeszer et al (2007) state that data from original collections of
these fish suggests a range extending from Pakistan in the west to
Myanmar (Burma) in the east, and from Nepal in the north to the Indian
state of Karnataka in the south. However, they caution that given the
historical nature of many of these records, along with the possibility that
specimens may have been misidentified (particularly with regard to their
presence in the most extremes of this distribution) this suggested range
may not be an entirely accurate reflection of their true present day
distribution.
• They can typically be found in standing or slow-moving bodies of water,
such as pools, ponds, lakes, ditches or rice paddies and would appear to
be a floodplain rather than a true riverine species (Vargesson 2007,
Delaney et al 2002, Spence et al 2006a). Field studies have found zebrafish
at sites that are silt-bottomed and well-vegetated, with shallow and
relatively clear water where they appear to occupy the whole of the
vertical water column (Engeszer et al 2007, Spence et al 2007).

5. • More than just pets
• Covered with iridescent scales and black
stripes, zebrafish (Danio rerio) are popular in
home aquariums. However, these little one- to
two-inch fish, natives of India’s Ganges River,
are also helping biomedical researchers learn
about how our hearts develop and function—
and what can make them fail.

6. Developing zebra fish embryo

7. How is your heart like that of a
zebrafish?
• Though distantly related, human and zebrafish
hearts have much in common. Both are muscles
designed to pump oxygen-carrying blood through
the body. In both cases, the heart is made up of
chambers with valves that ensure blood flows in
the correct direction. And, in both cases, the
heart pumps in a regular, rhythmic, way. The
rhythmic beating of the heart in part depends on
specialized heart muscle cells called myocytes
that are normally a highly organized part of the
heart’s structure.

9. • The zebrafish offers several distinct advantages as a genetic and embryonic model system to
study cardiovascular disease. One major advantage is that zebrafish are vertebrates that can
be used
for unbiased and whole-genome forward genetic screens.
• This allows the identification of novel genes that are required for cardiovascular
development. In addition, the function of unknown genes, identified by expression or
interaction screens, can be investigated by various reverse genetic approaches.
• Zebrafish embryos are particular well suited for studying gene function during cardiovascular
development, because zebrafish embryos are not completely dependent on a functional
cardiovascular system for their development. In
• zebrafish embryos that lack blood circulation, oxygen can still enter the embryos and reach all
tissues by passive diffusion owing to the small size of the embryo. This feature permits the
embryos to survive the initial phase of embryonic development and allows the analysis of
embryos with severe cardiovascular defects. This is in contrast to avian and mammalian
embryos, which die rapidly in the absence of a functional cardiovascular system. Besides the
ease of identifying and studying genetic mutants, the optical transparency of zebrafish
embryos has given new insights into various cellular aspects of cardiovascular development.

10. Can a zebrafish help solve medical
mysteries?
• Because zebrafish hearts are so similar to our
own, scientists are using the fish to study
many aspects of heart disease, particularly the
role of genetic mutations that might cause
heart abnormalities.
• One disease, called familial hypertrophic
cardiomyopathy (HCM), is the leading cause of
sudden death in young athletes.

11. Can a zebrafish help solve medical
mysteries?
• Scientists had been studying a collection of zebrafish mutants that
developed heart abnormalities. The most severe of this collection
was a defect named silent heart; embryos with this mutation had
hearts that did not beat at all. Using molecular techniques,
researchers found the gene that, when mutated, produces silent
heart also encodes the zebrafish version of the troponin T protein. In
the case of silent heart, they found the gene so mutated that it
failed to make any useful troponin T, and that this affected the
production of two other important heart proteins. The failure of this
system of proteins created disorganized heart muscle cells
(myocytes) that in turn failed to organize into a heart effective at
circulating blood. In humans with HCM, myocytes are also
disorganized, which can lead to an abnormal heartbeat, and in
some cases, sudden death.

12. • Thus zebra fish is a major expeimental model
used for studying about different scientific
fields

14. THANK YOU