For the first time, chromosomal defects responsible for hemophilia
have been corrected in patient-specific iPSCs using CRISPR-Cas9
nucleases. Asian Scientist Newsroom | August 4, 2015 | In the Lab
AsianScientist
(Aug. 4, 2015) - Sufferers of hemophilia live in a perpetual state of
stress and anxiety: their joints wear down prematurely and they have
bleeding episodes that feel like they will never end. Their bodies lack
the ability to make the clotting factor responsible for the coagulation
of blood so any cut or bruise can turn into an emergency without
immediate treatment.
Hemophilia A occurs in about 1 in
5,000 male births and almost half of severe cases are caused by
identified chromosomal inversions. In a chromosomal inversion, the order
of the base pairs on the chromosome are reversed so the gene doesn’t
express properly and the sufferer lacks the blood coagulation factor
VIII (F8) gene, which causes blood to clot in healthy people.
A
Korean team led by director of the Center for Genome Engineering Kim
Jin-Soo, Institute for Basic Science (IBS) and Professor Kim Dong-Wook
at Yonsei University has experimented with hemophilia A-derived induced
pluripotent stem cells (iPSCs) and hemophiliac mice and found a way to
correct this inversion and reverse the clotting factor deficiency that
causes hemophilia A.
This was the first time that
iPSCs—which possess the ability to change into any cell type in the
body—have been used in such a procedure. The researchers first collected
urinary cells from patients with chromosomal inversions causing
haemophilia, transforming them into iPSC cells. Then, they used
CRISPR-Cas9 nucleases (Clustered Regularly Interspaced Short Palindromic
Repeats-CRISPR associated protein 9) to flip the F8 gene around,
allowing it to be read correctly.
The corrected-iPSCs were
then induced to differentiate into mature endothelial cells which
expressed the F8 gene in the correct orientation. To verify that the
process worked, the endothelial cells with the inversion-corrected genes
were transplanted into F8 deficient mice (mice with hemophilia A) and
the mice started producing the F8 clotting factor on their own, which
essentially cured them of hemophilia A.
“We used
CRISPR RGENs [RNA-guided engineered nucleases] to repair two recurrent,
large chromosomal inversions responsible for almost half of all severe
hemophilia A cases,” Kim Jin-Soo said.
“To the
best of our knowledge, this report is the first demonstration that
chromosomal inversions or other large rearrangements can be corrected
using RGENs or any other programmable nuclease in patient iPSCs,” Kim
Dong-Wook added.
Importantly, the studied showed no
evidence of off-target mutations resulting from the procedure,
suggesting that it was only the desired parts of genome were changed.
These
findings open the door for further testing and if the results are
anything like the mice trials, the future of this treatment looks
promising.
The article can be found at: Park et al.
(2015) Functional Correction of Large Factor VIII Gene Chromosomal
Inversions in Hemophilia A Patient-Derived iPSCs Using CRISPR-Cas9
Source:
Institute for Basic Science; Photo: Shutterstock. Disclaimer: This
article does not necessarily reflect the views of AsianScientist or its
staff.
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