In this SlideShare, we'll recap the basics of gene editing and cover important basics such as the terminology, forward vs reverse genetics, as well as mechanisms of gene editing (homology-directed & non-homologous end joining). We'll also compare the popular gene-editing platforms including ZFNs, TALENs and CRISPR/Cas system, along with the potential applications of gene editing from clinical therapy to food sustainability.

1. Recent Technologies & Potential Applications
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Genome Editing Review
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2. Genome Editing Review
Content Overview
• Recap: What is Gene Editing?
• Brief History
• Forward vs Reverse Genetics
• The 3 Distinct Terms
• Outcomes: Homologous vs
non-Homologous
• Genome Editing Technologies
• Applications of Gene Editing
Technology
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3. Recap: What is Gene Editing?
Gene editing (or genome
editing) is a group of
technologies that give
scientists the ability to
change an organism's
DNA.
These technologies allow
genetic material to be added,
removed, or altered at specific
locations in the genome.
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Credit: iStock Photos
Source: https://medlineplus.gov/genetics/understanding/genomicresearch/genomeediting/

4. A Brief History of Gene Editing
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Source: https://geneeditinginstitute.com/about/our-history/

5. Key Figures in Gene Editing
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Gene Editing
Market projected
at USD 19.4 billion
in 2028
- Increase from USD 5.2
billion in 2020
- CAGR of 22.9%
(2021-2028)
- Increased use of
CRISPR tech. against
coronavirus
Grand View Research
USD 5.1 billion in
2021
Big pharma & biotech
invest in gene editing
tech. for COVID-19
vaccine R&D.
CRISPR has largest
revenue share
Market share of 48.8% in
2020, revenue up to USD
1.5 billion (followed by
ZFNs at USD 1.3 billion).
Source: Grand View Research, Global Market Insights & MarketsAndMarkets
5
Key Drivers in
Gene Editing:
- R&D to combat
COVID-19 (from
diagnostic to kill-
sequence)
- Increased prevalence
of chronic & genetic
disorders
- Rising government
support in gene R&D
- Growing demand for
synthetic genes
Global Market Insights

6. Terms & Concepts
Understanding Gene Editing at its Core
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7. Forward Genetics vs Reverse Genetics
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Phenotype ‣ Genotype
Forward genetics
identifies & links a
mutation to a disease.
Altered or abnormal
phenotype examined
by screening genes.
Genotype ‣ Phenotype
Reverse genetics
induces mutations in
model organisms to
study their role in
disease. The genotype
is altered.
FORWARD
REVERSE
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5002245/
Phenotype: observable physical properties
i.e., appearance, development, behavior.
Genotype: the genetic markup of an organism,
describes an organism’s complete set of genes.

8. Three Distinct Terms
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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596157/
Genome Engineering
Sequence of
genomic DNA is
designed and
modified
Genome Editing
Site-specific
modifications into
genomic DNA
using DNA repair
mechanisms
Gene Editing
Modification of a
single gene
(enough DNA to
code for one
protein)

9. Major Mechanisms of Gene Editing
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Source: https://www.nature.com/articles/s41392-019-0089-y
Nuclease-induced DNA
double strand breaks
(DSBs) activates one of
two major repair
mechanisms that occur in
almost all cell types:
• nonhomologous end-
joining (NHEJ) that is
error prone, OR
• homology-directed
repair (HDR) that is more
precise

10. Gene Editing Technologies
Overview of MegNs, ZFNs, TALENs & CRISPR/Cas
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11. Meganucleases (MegNs)
Endodeoxyribonucleases with
large recognition site (DNA
sequences of 12-40 base pairs);
making the site generally
occurring only once in any
given genome.
Given its high specificity, the
probability of finding an enzyme that
targets a desired locus is small and
production of customized MegNs
remains complex & highly inefficient.
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Credit: Castro et al., IJMS
Source: https://en.wikipedia.org/wiki/Meganuclease
First identified in the 1990s, researchers discover that
applications of MegNs in genome editing is limited
and technically challenging to work with.

12. Zinc finger Nucleases (ZFNs)
Artificially engineered
restriction enzymes for
custom site-specific genome
editing. ZFNs themselves are
transcription factors, where
each finger recognizes 3-4
bases.
While ZFNs are easier to design
compared to MegNs, its prone to
cause off-target cleavages that
leads to apparent toxicity to cells.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596157/
Credit: Papaioannou, et al., ResearchGate
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13. Transcription Activator-Like Effector nucleases (TALENs)
TALENs are similar to ZFNs and
MegNs in that the proteins must
be re-engineered for each
targeted DNA sequence.
It is however, complicated for whom
not familiar with molecular biological
experiments. It is also confronted
with some limitations, such as their
large size (impeding delivery) in
comparison to ZFNs.
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Compared ZFNs, a single TALEN module can recognize
one nucleotide, making them simpler to design with
lower number of off-target breaks.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596157/

14. CRISPR/Cas system
Short for clustered regularly
interspaced short palindromic
repeats, the CRISPR/Cas
system is the most recent (and
most popular) platform in the
field of genome editing. It is
low cost, easy to design and
highly scalable.
Unlike ZFNs & TALENs, the DNA
sequence recognition of the
CRISPR/Cas system is based on
RNA-DNA interactions.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596157/
Credit: StockAdobe.com
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The CRISPR/Cas system was developed in 2013
and is known as the third-generation genomic
editing tool.

15. Gene editing Platforms Compared
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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596157/
Feasibility
MegNs
(obsolete)
ZFNs TALENs CRISPR/Cas9
Design Simplicity --- - + ++
Cost & affordability -- + - ++
Scalability -- - -/+ +
Site recognition length (bp) 12-40 18-36 28-40 Up to 44
Targeting & cleavage efficacy -/+ - + ++
Programmability --- -- - +
Success Rate (est.) n/a 24% 99% 90%

16. Gene Editing Applications
From Clinical Research & Therapy to Food Sustainability
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17. Various Applications of Gene Editing
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Crops
Viral
Diseases
Gene
Therapy
Cancer
Research
Rare
Diseases
Source: https://www.nature.com/articles/s41392-019-0089-y

18. Gene Editing in Clinical Therapy
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Source: https://www.nature.com/articles/s41392-019-0089-y
Ex vivo: Cells are
isolated from a patient
to be treated, edited
and re-engrafted back
to the patient. For
therapeutic success, the
target cells must survive
in vitro and return to the
target tissue after
transplantation.
In vivo: Engineered
nucleases are delivered
(viral or non-viral) and
directly injected into the
patient for systemic or
targeted tissue (such as
the eye, brain, or
muscle) effect.
Credit: Li, et al., Nature.com (2020)

19. Gene Editing in Cancer Immunotherapy
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One promising area in
immunotherapy is the application
of genetically engineered T cells,
known as chimeric antigen
receptor (CAR) T cells, which
allow the targeting of tumor-
associated antigens and could
enhance the therapy response.
Using CRISPR/Cas9, Liu and his
colleagues efficiently generated
CAR T cells in which 2 or 3 genes
were simultaneously disrupted
and tested their antitumor
function both in vitro and in vivo.
Source: https://www.nature.com/articles/s41392-019-0089-y
Credit: Li, et al., Nature.com (2020)

20. Using CRISPR for food sustainability
The agriculture industry needs
to solve an extremely complex
problem — feeding more
people while facing
increasingly dire resource
constraints.
While conventional plant breeding
relies on introducing random
changes into plant DNA, CRISPR
technology offers precise alterations
to specific DNA sequences.
Source: https://www.genengnews.com/topics/genome-editing/from-
pharma-to-farm-can-crispr-feed-the-world/
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Inari focuses on soy,
corn & wheat – major
crops that feed the
world & impact the
environment the most.
TreeCo is using CRISPR
technology to enhance
trees so it can be bred
about 10x faster

21. • Genome editing is a fast-growing field. Much progress has been
accomplished in the improvement of gene editing technologies
since their discovery.
• The tremendous advances in the development of engineered
nucleases (especially ZFNs, TALENs, and CRISPR/Cas9) paved the
way for genome editing from a theoretical concept into clinical
practice.
• CRISPR/Cas9 system has been increasingly popular in recent
years, due its relatively low cost. Researchers found that it is easy
to design, highly scalable and has a relatively high success rate.
• Gene editing applications include manufacturing engineered
medical products, eradication of human genetic diseases,
treatment of AIDS and cancers, as well as improvement of crop
and food in coming years.
Conclusion
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22. By xeraya capital
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