The document provides an overview of zebrafish (Danio rerio) as a model organism, detailing its taxonomy, genetic similarities to humans, and various applications in biological research, such as cancer studies and regenerative medicine. Key advantages for using zebrafish include their translucent embryos, rapid growth, and genetic similarity to humans, which make them ideal for studying development and disease. The document also highlights the historical context of zebrafish research and its future prospects in various scientific disciplines.

1. ZEBRAFISH: AS A MODEL ORGANISM
PRESENTED BY GUIDED BY
Namrata Singh Prof. (Mrs) Pravati Kumari Mahapatra
M.Sc. Semester III P.G. Department of Zoology
Roll number -15 ZOO 016 Utkal University, Vani Vihar
Bhubaneswar- 751 004.
1

2. CONTENTS
1. Introduction
2. Taxonomy
3. History
4. Genetics of Zebrafish
5. Uses as a model organism
6. Future prospects
7. Conclusion
8. References.
2

3. INTRODUCTION
Danio rerio, commomly
known as Zebrafish is a tropical
fresh water fish belonging to
the minnow family.
It has become another
popular model organism to
study fundamental biological
questions.
It is a small 1–1.5 inches fish
that grows easily in aquaria.
Fig. 01 Zebrafish.
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4. TAXONOMY
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Danio
Species: rerio.
4

5. 1. The Zebrafish is named for the
five uniform, pigmented,
horizontal, blue stripes on the
side of the body, which are
reminiscent of a Zebra's stripes,
and which extend to the end of
the caudal fin.
2. It is laterally compressed with
its mouth directed upwards.
DESCRIPTION
Fig.02 A Zebrafish showing arrangement
of stripes.
5

6. The Zebrafish is native to the streams of the South-
Eastern Himalayan region. The species arose in the
Ganges region in eastern India and commonly inhabits streams,
canals, ditches, ponds and slow-moving or stagnant water
bodies. Zebrafish have been introduced to parts of the United
States.
DISTRIBUTION
6

7. HISTORY
1. The use of Zebrafish as a
model organism was
pioneered at the University of
Oregon,U.S.A. by George
Streisinger in 1970.
2. He is the “Founder Father” of
Zebrafish Developmental and
Genetic Research.
Photograph 01 George Streisinger.
7

8. In 1990, the first
large scale
mutagenesis of
Zebrafish were
conducted by
Christiane Nusslein
Volhard in Oxford
University, United
Kingdom to identify
developmental
mutations .
Photograph 02 Christiane Nusslein Volhard.
8

9. Thomas Look of
Dana-Farber Cancer
Institute, Boston
uses the
translucent
Zebrafish to study
how cancer
behaves in 1995.
Photograph 03 Thomas Look.
9

10. FLOWN INTO SPACE
On 22nd July, 1976, the
Space Station, Salyut 5
was launched in which
Zebrafish was one of
the crew members.
Fig. 03 Salyut 5.
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11. Fig.04 Anatomy of male Zebrafish.
11

12. Zygote
Blastula
Gastrula
Hatching
Larva
Juvenile
Adult
Cleavage
Segmentation
Fig.05 Developmental stages of Zebrafish.
12

13. MODEL ORGANISM
1. A model organism is a non-human species that has been
widely studied, usually because it is easy to maintain and
breed in a laboratory setting and has particular experimental
advantages.
2. They are used in the laboratory to help scientists understand
biological processes.
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14. ADVANTAGES
Advantages of Zebrafish as a model organism:
1. Optically translucent embryos
2. Rapid hatching of eggs
3. Maintenance cost is significantly lower than those for
mammals.
4. Amenable for molecular and genetic analysis.
5. As Zebrafish eggs are fertilized and develop outside the
mother’s body it is an ideal model organism for studying
early development.
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15. GENETICS
1. 70% of protein-coding human genes are related to genes
found in the Zebrafish.
2. 84% of genes known to be associated with human disease
have a Zebrafish counterpart.
3. They can be cloned from somatic cells.
4. They can be made transgenic.
5. As a vertebrate, the Zebrafish has the same major organs
and tissues as humans. Their muscle, blood, kidney and eyes
share many features with human systems.
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16. ZEBRAFISH AS A MODEL IS USED TO STUDY
1. Regeneration of heart
2. Tail regeneration
3. Retinal regeneration
4. Human pigmentation
5. Cancer research
6. Autism.
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17. HEART REGENERATION
Mammals respond to a myocardial
infarction by irreversible scar formation. By
contrast, the Zebrafish are able to resolve the
scar and to regenerate functional cardiac
muscle.
The reparative and regenerative process
is achieved through Smad3-dependent TGFβ
signaling.
17

18. 7. During a heart attack, heart muscle cells are deprived of oxygen and
they die, leaving scar tissue
8. Scientists are working to find out the specific factors involved in this
process to see if this will help us to develop ways of repairing the
heart in humans with heart failure or who have suffered heart
attacks.
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19. MECHANISM
Zebrafish heart regeneration can be sub-divided
into three overlapping phases:
A. Inflammatory phase
B. Reparative phase
C. Regenerative phase.
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20. INFLAMMATORY PHASE
First, myocardial
cell death triggers
an inflammatory
response that is
characterized by the
infiltration of the
infarct with
activated leukocytes
and fibroblasts-like
cells which express
TGFβ ligands
Fig.06 Mechanism of inflammatory
phase. 20

21. REPARATIVE PHASE
Second as the
wound becomes
cleared of the
dead cells and
matrix debris, the
reparative phase
begins, TGFβ
stimulates the
recruited
fibroblast-like cells
to synthesize
collagen rich ECM.
Fig. 07 Mechanism of reparative
phase. 21

22. REGENERATIVE PHASE
At the onset of scar
formation, the
regenerative phase
begins. While the
fibrotic tissue is still
maturing TGFβ signaling
promotes proliferation
of the cardiomyocytes
located in the vicinity of
the post-infarct.
Fig.08 Mechanism of regenerative
phase. 22

23. Tissue remodeling and invasion of new cardiac muscle
to replace scar issue are associated with TGFβ dependent
expression of Tenascin-C, an extracellular protein with
contra-adhesive properties.
Thus, the regenerative phase is characterized by two
opposing processes:
1. scar deposition in the damaged area
2. scar degradation at the position where new
cardiomyocytes invade the post-infarct.
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24. TAIL FIN REGENERATION
1. Zebrafish fins are complex appendages that quickly and reliably
regenerate after amputation, restoring both size and shape.
2. The key regenerative units are their many rays of dermal bone,
which are segmented and lined by osteoblasts.
3. An amputated fin ray is covered within the first several hours by
epidermis, and within one to two days, a regeneration blastema
forms. The blastema is a proliferative mass of morphologically
similar cells, formed through disorganization and distal migration
of fibroblasts and osteoblasts.
4. Blastema formation is the only one step in zebrafish tail fin
regeneration.
5. Wnt signaling positively regulate blastemal proliferation and
outgrowth.
24

25. Fig.09 Amputation of Zebrafish tail fin. 25

26. Fig. 10 Blastema formation in Zebrafish tail fin. 26

27. Fig.11 Wnt signaling regulating tail fin regeneration. 27

28. RETINAL REGENERATION
Another notable characteristic of the Zebrafish is that it possesses
four types of cone cells, with ultraviolet-sensitive cells
supplementing the red, green and blue cone cell subtypes found
in humans. Zebrafish can thus observe a very wide spectrum of
colors. The species is also studied to better understand the
development of the retina; in particular, how the cone cells of the
retina become arranged into the so-called cone mosaic.
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29. The researchers studied Müller glial cells in the eyes of humans
aged from 18 months to 91 years, and were able to develop
them into all types of retinal neurons. The stem cells of
Zebrafish successfully migrated into diseased rats' retinas, and
took on the characteristics of the surrounding neurons. The
team stated that they intended to develop the same approach
in humans.
Stem cells from Zebrafish, the staple of genetic research, could
regenerate damaged cones in retinas and restore eyesight to
people.
Fig.12 Regeneration of retina.
29

30. Zebrafish solves the mystery of our skin
color. Embryonic patterning of pigmentation
in D. rerio is highly investigated area of study.
SLC24A5 is shared both by humans and
Zebrafish and makes melanosomes less
abundant, less concentrated and smaller in
lighter skinned humans or light-striped
Zebrafish.
HUMAN PIGMENTATION
30

31. While some researchers were studying Zebrafish to find cancer
genes, they found that pigment cells of Zebrafish looked similar to
pigment cells in light-skinned humans. Since then, many
researchers have investigated the Zebrafish gene responsible for
different colors in stripes.
In 2005, some studies found the human version of the
gene, which affected Europeans differently from Africans and
Asians.
Fig.13 Location of pigment cells in Zebrafish embryo.
31

32. At embryonic and early larva
stage, the neural crest cells gets
differentiated into three cells
displaying alternating stripes:
1. Melanocytes (blue)
2. Iridiophores (silver)
3. Xanthophores (yellow).
Further study in Zebrafish
pigment cells is essential, since
they provide many opportunities
to learn the nature of the human
skin color.
Fig.14 Patterns of Zebrafish.
32

33. 1. Zebrafish have been used to make
several transgenic models of cancer,
including melanoma, leukemia,
pancreatic cancer, colon cancer.
2. Researchers have created a model of
cancer in Zebrafish that allows them to
capture live images of tumors forming
and growing.
IN CANCER RESEARCH
Fig.15 Tumor in Zebrafish.
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34. STAINING THE CELL
1. In Zebrafish, the endothelial cells are
stained with a fluorescent protein.
2. The fluorescent stained tumor cells are
highlighted in the transparent Zebrafish
embryos and larvae.
3. Now, the process of metasizing tumor cells
can be accurately tracked at cellular level.
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35. XENOTRANSPLANTATION AND METASTASIS
During zebrafish
development, a cluster of neural
cells called the "posterior lateral
line primordium" (PLLp) mimics
the behavior of metastasizing
human cancer.
The cluster of zebrafish
neural cells travels the entire
length of the embryo, driven by
the same molecular pathways
that drive human cancer cells to
new sites in the body.
So, if we can find drugs that
block it then we can also find
drugs that potentially block
cancer metastasis in humans as
well.
Fig. 16 Transplantation and metastasis.
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36. DISCOVERY OF A DRUG
Rosuvastatin prevents the
spreading of cancerous cells in
Zebrafish from one part to
another.
The same drug was then
tested on human cancer cells,
and it had the same migration-
stopping effect on both
leukemia and pancreatic
cancer cells.
Fig. 17 3D Structure of
Rosuvastatin.
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37. AS A MODEL TO STUDY AUTISM
Zebrafish model gives new insight on autism spectrum
disorder. A team of researchers at Massachusetts Institute of
Technology focused on genes that have been found to be either
missing or copied in about 1% of patients with autism. Their study
revealed that when they deleted these genes from Zebrafish
embryos, nearly all the fish developed brain abnormalities.
It is found that estrogens, the primary female sex
hormone, could reverse abnormal behavior in Zebrafish carrying a
mutation in CNTNAP2, a gene linked to genes of autism in
humans,SYNGAP1 and SHANK3.
The researchers found that Zebrafish carrying the
CNTNAP2 mutation are more prone to seizures than Zebrafish
without the mutation.
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38. Fig.18 Zebraboxes. 38

39. Genome sequencing
1. The Wellcome Trust Sanger Institute, U.K. was the first to
start the Zebrafish Genome Sequencing Project.
2. In 2009, Institute of Genomics & Integrative
Biology, New Delhi reported sequenced genes in Zebrafish.
3. The paper “The zebrafish reference genome sequence and
its relationship to human genome” was published in Nature
in 17th April, 2013.
Its genome (1.4 x 109 base pairs) has been
sequenced revealing 26,606 protein-coding genes. The
Zebrafish genome has been fully sequenced to a very high
quality. This has enabled scientists to create mutation in more
than 14,000 genes to study their function.
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40. GloFish
1. The GloFish is
a patented brand
of genetically modified
fluorescent fish. Different
varieties of GloFish are
currently available in the
market. Zebrafish were
the first GloFish available
in pet stores.
2. These fish are a valuable
tool for examining
erythrocyte development
and circulation defects in
the developing embryo.
Fig.19 GloFish in aquarium.
40

41. GENE EXPRESSION
1. Due to their short lifecycles and relatively large clutch sizes,
Zebrafish are a useful model for genetic studies.
2. Morpholino antisense technology reduces gene expression.
Morpholino oligonucleotides (MO) are stable,
synthetic macromolecules that contain the same bases as DNA
or RNA; by binding to complementary RNA sequences, they can
reduce the expression of specific genes or block other processes
from occurring on RNA.
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42. DRUG DISCOVERY
As demonstrated through ongoing
research programmes, the Zebrafish model
enables researchers not only to identify genes
that might underlie human disease, but also
to develop novel therapeutic agents in drug
discovery programmes.
42

43. ENVIRONMENTAL MONITORING
1. The researchers cloned estrogen-sensitive genes and
injected them into the fertile eggs of Zebrafish.
2. The modified fish turned green if placed into water that was
polluted by estrogen.
43

44. ZEBRAFISH WEBSITES
1. The Zebrafish Server
2. The Fishnet
3. ZFIN- Zebrafish Information Network.
44

45. Zebrafish Labs in India
1. Institute of Genomics and Integrative Biology
(New Delhi)
2. Center for Cellular and Molecular Biology
(Hyderabad)
3. Indian Institute of Sciences (Bangalore)
4. Tata Institute of Fundamental Research
(Mumbai)
5. Institute of Life Sciences (Hyderabad)
6. National Centre for Radio Astrophysics
(Pune). 45

46. FUTURE PROSPECTS
As Zebrafish are now being used in virtually
all disciplines, from neurogenesis to oncogenesis, from
behavior to genetics, its popularity is steadily
increasing.
The emergence of Zebrafish Conferences and
the increasing presence of Zebrafish studies at large
annual meetings are also boosting the use of Zebrafish
as an appropriate model organism.
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47. CONCLUSION
It is a tiny fish with a big splash.
47

48. REFERENCES
Chablais F, Jazwinska A (2012) The regenerative capacity of the zebrafish
heart is dependent on TGFβ signaling. Development and Stem
Cell, 139(10): 1921-1930.
Gilbert SF(2010) Developmental Biology. 9th Edition. Sinauer Associates, Inc.
Sunderland, Massachusetts, USA, pp 323- 332.
Hsu CH, Wen ZH, Lin CS, Chakraborty C (2007) The zebrafish model: use in
studying cellular mechanism for a spectrum of clinical disease entities.
current neurovascular reseasrch, 4(2): 111-120.
Slack JMW (2006) Essential Developmental Biology. 2nd Edition. Blackwell
Publishing Ltd., Malden, USA, pp 61-89.
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49. THANKYOU
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