Gene therapy is the technique to remove/ replace the faulty gene with the healthy one.

1. GENE THERAPY
Presented by
Tayaba Usman
Msc Micro
BI592545

2. What is Gene therapy?
•An experimental procedure aimed at
replacing, manipulating, or
supplementing nonfunctional or
malfunctioning genes with healthy
genes.

3. INTRODUCTION…….
The earliest method of gene therapy, often called gene
transfer or gene addition, was developed to:
• Introduce a new gene into cells to help fight a disease.
• Introduce a non-faulty copy of a gene to stand in for the
altered copy causing disease.
• Later studies led to advances in gene therapy techniques.
i.e genome editing (an example of which is CRISPR-
Cas9),
• In this method instead of introducing new genetic
material into cells, genome edditing is done by molecular
tools to change the existing DNA in the cell.

4. Introduction………
• Genome editing is being studied to:
• Fix a genetic alteration , so the gene can function
properly.
• Turn on a gene to help fight a disease.
• Turn off a gene that is functioning improperly.
• Remove a piece of DNA that is impairing gene
function and causing disease.

5. TYPES OF GENE THERAPY

6. TYPES OF GENE THERAPY

7. TYPES OF SOMATIC GENE
THERAPY

8. EX – VIVO THERAPY

10. EXAMPLE of Ex –VIVO
THERAPY

12. IN-VIVO THERAPY

15. GENE THERAPY TECHNIQUES
Gene augmentation therapy
• This is used to treat diseases caused by a mutation
that stops a gene from producing a functioning
product, such as a protein.
• This therapy adds DNA containing a functional
version of the lost gene back into the cell.
• The new gene produces a functioning product at
sufficient levels to replace the protein that was
originally missing.
• This method is used to treat disease like cystic
fibrosis.

16. GENE INHIBITION THERAPY
• The basis of this therapy is to eliminate the activity
of a gene
• The aim is to introduce a gene whose product either:
• inhibits the expression of another gene
• For example, cancer is sometimes the result of the
over-activation of an oncogene? (gene which
stimulates cell growth). So, by eliminating the
activity of that oncogene through gene inhibition
therapy, it is possible to prevent further cell growth
and stop the cancer in its tracks.

18. KILLING OF SPECIFIC CELLS
• The aim is to insert DNA into a diseased
cell that causes that cell to die.
• This can be achieved in one of two ways:
• the inserted DNA contains a “suicide” gene
that produces a highly toxic product which
kills the diseased cell
• the inserted DNA causes expression of a
protein that marks the cells so that the
diseased cells are attacked by the body’s
natural immune system.

20. Recent developments
• CRISPR/Cas9 Genome Therapy
• The mechanism of CRISPR/Cas-9 genome editing can be
generally divided into three steps: recognition, cleavage, and
repair
• The CRISPR-Cas9 system consists of two key molecules
that introduce a change (mutation?) into the DNA. These
are:
• an enzyme? called Cas9. This acts as a pair of ‘molecular scissors’
that can cut the two strands of DNA at a specific location in the
genome so that bits of DNA can then be added or removed.
• a piece of RNA? called guide RNA (gRNA). This consists of
a small piece of pre-designed RNA sequence (about 20
bases long) located within a longer RNA scaffold.

21. • The scaffold part binds to DNA and the pre-designed sequence
‘guides’ Cas9 to the right part of the genome. This makes sure
that the Cas9 enzyme cuts at the right point in the genome.
• The guide RNA is designed to find and bind to a specific
sequence in the DNA. The guide RNA has RNA bases? that
are complementary? to those of the target DNA sequence
in the genome. This means that, at least in theory, the
guide RNA will only bind to the target sequence and no
other regions of the genome.
• The Cas9 follows the guide RNA to the same location in
the DNA sequence and makes a cut across both strands
of the DNA.
• At this stage the cell? recognises that the DNA is damaged
and tries to repair it.

23. VECTORS IN GENE THERAPY
• Two type of vectors
• Viral vectors
• Non viral vectors

24. VIRAL VECTORS
● Retroviruses - A class of viruses that can create double-
stranded DNA copies of their RNA genomes. These copies of its
genome can be integrated into the chromosomes of host cells.
Human immunodeficiency virus (HIV) is a retrovirus.
● Adenoviruses - A class of viruses with double-stranded DNA
genomes that cause respiratory, intestinal, and eye infections in
humans. The virus that causes the common cold is an
adenovirus.
● Adeno-associated viruses - A class of small, single-stranded
DNA viruses that can insert their genetic material at a specific
site on chromosome .
● Herpes simplex viruses - A class of double-stranded DNA
viruses that infect a particular cell type, neurons. A common
human pathogen that causes cold sores.

25. NON – VIRAL VECTORS

26. 3) HUMAN ARTIFICIAL CHROMOSOME
• Can carry a large DNA i.e. with one or more
therapeutic gene with regulatory elements.
NON – VIRAL VECTORS

31. References
• Kaufmann KB, B ing H, Galy A, Schambach A, Grez M. Gene
therapy on the move. EMBO Mol Med. 2013 Nov; 5(11): 1642-
1661
• Santhosh R Patil, Ibrahim A. Al-Zoubi, Raghuram PH, Neeta
Misra, Nidhi Yadav, Mohammad Khursheed Alam.Gene
Therapy : A Comprehensive Review.2018 International
Medical journal vol25pp.361-364
• https://medlineplus.gov/genetics/understanding/therapy/gen
etherapy/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC838812