A new study of dogs released in Science this week offers a startling insight into how life-changing CRISPR gene editing technology could be for some people in the near future. It suggests that CRISPR may be used to treat an otherwise incurable, deadly genetic disorder known as Duchenne Muscular Dystrophy (DMD).
DMD is the most common form of muscular dystrophy, a term used to describe conditions that continually destroy muscles throughout the body. This waste is mainly caused by the inability to use dystrophin, a protein that acts as an adhesive to stabilize muscle fibers. These conditions are often caused by a genetic defect, and people with DMD have mutations in the gene responsible for dystrophin, which prevents them from doing anything at all. Because the dystrophin gene is found on the X chromosome, DMD mainly affects boys because girls typically have two X chromosomes and a healthy copy of the dystrophin gene is usually sufficient to prevent serious disease (women still can Being the Carrier and Sharing the Disease) (19659005) The symptoms of DMD are around the age of four and are getting worse over time, with many people eventually losing the ability to stand, walk and even swallow their food. And only a few live after the age of 30. But as you can see in girls, dystrophin production does not need much dystrophin production to ward off these symptoms. It was hoped that gene therapy could significantly improve the lives of those affected or even cure the disease completely. The advent of the CRISPR-Cas system, a relatively cheap and simple gene editing method, has only increased this hope.
There have been successful studies with mice that used CRISPR to repair DMD mutations that appeared to be restored to some muscle functionality – including the team behind this latest study. Their new study is the first to test whether it can be found in larger animals.
A few years ago it was discovered that dogs can be born with mutations that led them to develop their own version of DMD ideal test animal. This mutation deletes a specific DNA region on the dystrophin gene that encodes the protein, called exon 50. Without this exon, exon 51 is also out of balance and makes the production of dystrophin impossible.
Researchers bred four beagle with DMD, then used CRISPR to manipulate exon 51 and puzzle it out. These errors, it was theorized, would cause the affected cells to completely skip the exon 51. The expected net result would be a reduced but still functional level of dystrophin production. And that seems to have happened.
The dogs were given CRISPR – via a harmless virus that is native to cardiac and muscular tissue – at the age of one month. Six to eight weeks later, the researchers found that heart and diaphragm dystrophin levels were 92 percent and 56 percent normal again in the dog receiving the largest dose. It is believed that even 15 percent of normal dystrophin production would be life-threatening for DMD patients.
"Our strategy differs from other therapeutic approaches to DMD because it restores the mutation that causes the disease and restores normal expression of the repaired dystrophin," said lead author Leonela Amoasii, a researcher at Southwestern Medical Center, University of Texas, in a statement. "But we still need to do more before we can do it clinically."
On the one hand, the study should only serve as a preliminary demonstration, so the dramatic results should be taken with caution for the time being. The dogs were not observed long enough to know for sure if this recovery would lead to a lasting improvement in symptoms. (They have been euthanized so as not to expose them to any possible condition that may result from the condition and treatment.) Furthermore, only about 15 percent of people with DMD have this particular mutation, so other gene editing would be needed to complete the rest of to help the world's 300,000 boys believed to have this disease
And for the praise that CRISPR has received, there are real, though sometimes exaggerated, fears that it could lead to unwanted gene mutations that increase the risk for cancer or others Could increase health problems. When CRISPR treatments for DMD targeted a person's stem cells, the authors noted in their study that both the positive and the harmful effects could be permanent. There were no specific mutations outside the target sequence in the dogs, but it is a risk that other future studies must continue to pay attention to.
Yet, the researchers who started a business to commercialize their technology have called Exonics Therapeutics. endeavor to conduct ongoing and longer-term studies involving not only DMD but also other genetic disorders. [Science]