Jin-Soo Kim, a molecular biologist at Seoul National University, used gene-editing technology to create super-muscly pigs by introducing a mutation in the myostatin (MSTN) gene. He used a technology called TALENs, which uses a DNA-cutting enzyme attached to a DNA-binding protein to cut the MSTN gene. The cell's repair system stitches the DNA back together but sometimes deletes or adds base pairs, rendering the gene dysfunctional. The team is now doing the same experiment with CRISPR/Cas9 technology. CRISPR/Cas9 uses CRISPR sequences and a Cas9 enzyme to target and cut specific DNA sequences.

1. Super-muscly pigs created
by small genetic tweak
Masume mohamadian

3. Jin-SooKim,a molecularbiologist at SeoulNationalUniversity

4. MSTN
Cytogenetic Location: 2q32.2
The official name of this gene is “myostatin.”

5. • Transcription activator-like effectors
To introduce this mutation in pigs, Kim used a gene-
editing technology called a TALEN, which consists of a
DNA-cutting enzyme attached to a DNA-binding protein.
The protein guides the cutting enzyme to a specific gene
inside cells, in this case in MSTN, which it then cuts. The
cell’s natural repair system stitches the DNA back
together, but some base pairs are often deleted or added in
the process, rendering the gene dysfunctional.
TALEN

6. Structure of TALEN
• In nature, TALs are DNA binding proteins from
bacteria that infect plants
• DNA binding is mediated by 34 bp amino acid
repeats, which differ at amino acids 12 and 13.
These “repeat variable diresidues”, or RVDs
• Each RVD binds one nucleotide

8. Nuclease domains are FOK 1 s

9. Repair
 The first is homologous recombination (HR)
 The second major mechanism for DSB repair is nonhomologous end joining
(NHEJ)
double-strand breaks (DSBs)

10. CRISPR/Cas9
the team is now doing the same experiment with another,
newer gene-editing technology called CRISPR/Cas9

11. CRISPR/ Cas system

12. 
CRISPR/ Cas modules are adaptive immunity systems
that are encodedby mostarchaeaand many bacteriaand
that act against invading genetic elements,such as phage
and plasmids
40%bacteria and 90% archaea

13. • CRISPR= Clustered Regularly Interspaced Short
Palindromic Repeats
• Cas= CRISPR-associated proteins

14. CRISPR/ Cas system
There are 3 steps in the CRISPR–Cas invader
defense pathway:
• 1. Adaptation
• 2. RNA processing (CRISPR RNA biogenesis)
• 3. RNA interference (Invader silencing)

19. Which should I use, TALEN or CRISPR?
recent improvements in the technology, such as the use of
double nickases, truncated guide RNAs, and a Cas9-Fok I fusion,
improve CRISPR target site specificity.

20. RNAi and genome editing
• RNAi-mediated knockdown is the most common strategy for
ablating gene function in higher eukaryotes. However, there are a
few key differences between RNAi and genome editing. First, RNAi
does not completely shut off the gene . Rather, gene expression is
down-regulated post-transcriptionally, without changing the
genetic code. Some functional RNA or protein remains and is
translated. So, the RNAi strategy is a “knockdown”. Gene function is
reduced, not eliminated. In genome editing, on the other hand, the
genetic code is changed, and attenuation of gene expression is
usually complete, leading to a “knockout”. The decision on whether
to use RNAi or genome editing for attenuating gene expression
depends on the goals of the experiment.

22. References
• Super-muscly pigs created by small genetic tweak. Jin
soo kim at nature
• ZFN, TALEN and CRISPR/Cas-based methods for
genome engineering .Thomas Gaj
• Genome Editing Technology From GeneCopoeia,
Inc.
Ed Davis
• Editing our DNA with Molecular Scissors at The Tech
Museum of Innovation
• RNA-Guided Endonuclease at toolgene.com
• Advances in genome editing technology and its
promising application in evolutionary and ecological
studies. Lei Chen