Researchers from the U.S. and Germany have used the gene editing tool
CRISPR-Cas9 in a novel way to produce healthy heart muscle in Duchenne muscular
- Mutations responsible for Duchenne
muscular dystrophy (DMD) can be corrected using myoediting along with
CRISPR-Cas9 gene editing technology.
- Twelve different DMD mutation
hotspots can be rectified via myoediting to produce functional dystrophin.
- Novel approach may be a potential
therapeutic for over 60% of the DMD afflicted population.
The study is published in Science Advances
Duchenne muscular dystrophy (DMD)
DMD is a progressive muscle wasting genetic disease which leads to degeneration of cardiac and skeletal
Only boys are affected with DMD while
girls can be asymptomatic carriers. The disease is caused by over 3000
different mutations in the dystrophin gene.
Dystrophin is a protein that links the cytoskeleton of a muscle fiber to the
surrounding extracellular matrix of muscle cells through the cell membrane.
maintains the integrity of the plasma membrane, acts as a shock absorber and
prevents our muscles from breaking down as a result of wear and tear. Degeneration of the cardiac muscle, the
muscle most affected by lack of dystrophin is the most common cause of death in
Mutations and their effect on dystrophin
gene is the largest gene in our body that can be roughly divided into three
sections, the head, body, and tail. Mutations in the body are called internal
mutations and can result in a partially functional protein. In this case, the mutation causes a milder form of muscular dystrophy called Beckers
if the mutations are in the head or tail exons, also called the "essential"
regions of the gene, dystrophin is not produced and results in the severe and
more lethal form of the disease called Duchenne
Without dystrophin, the patient's muscle cells
become leaky and eventually die. This causes degeneration of muscle tissue
gradually spreading throughout the body. When the heart muscles degenerate, the
condition is fatal.
‘Myoediting technique can eliminate Duchenne muscular dystrophy causing mutations and restore the production of normal dystrophin protein.’
CRISPR-Cas9 gene editing
technology works by creating a nick at the desired spot on the genome where the
surrounding gene sequence has to be edited or repaired.
Mutations usually cluster themselves together in regions known as "hotspots."
The presence of 3000 odd mutations in DMD patients was making it difficult to
use the CRISPR tool in DMD. To overcome this problem, a novel technique called
"myoediting" was used along with CRISPR-Cas9 technology that can edit or repair
entire clusters of mutations. It removes
mutated sections of the dystrophin gene that cause DMD and restores normal
function to cells with DMD mutations.
The researchers took cells from DMD patients and
converted them to stem cells. The stem cells were then myoedited and
reprogrammed to grow into heart muscle
cells that were
able to produce dystrophin protein.
Thus when the cells made protein from the genes that
underwent myoediting, the hotspots
were 'skipped-over;' specifically, twelve mutation hotspots of
Duchenne muscular dystrophy (DMD) were corrected to produce functional
dystrophin protein. In the study, a tiny
bit of heart muscle tissue was then grown, and the resultant
tissue could beat and remained healthy.
this approach cannot correct all DMD mutations, it may be a potential therapeutic for over 60% of the DMD afflicted population
on the type of mutation present myoediting can either correct the gene to
produce a perfect dystrophin protein or a partially functional protein. If
several internal exons are skipped, there is some abnormality in the dystrophin
protein, and that would resemble Beckers muscular dystrophy. But, this too, is
a significant relief for those with DMD. In case of insertions and duplications
in the DMD gene, these can be perfectly corrected to restore a fully functional
- Correction of diverse muscular dystrophy mutations in human engineered heart muscle by single-site genome editing - (http://advances.sciencemag.org/content/4/1/eaap9004.full)
- Long, C. et al. Correction of diverse muscular dystrophy mutations in human engineered heart muscle by single-site genome editing. Science Advances 4, eaap9004 (2018).