Progress in gene editing CRISPR – The Daily Campus

For the first time, the progression of Duchenne muscular dystrophy (DMD) was stopped in a mammal as big as the dog using the CRISPR gene editor. DMD is a genetic disease that causes severe muscle weakness and breakdown. The mutations of the dystrophin gene, involved in the production of the dystrophin protein, are the known cause of the disorder. Abnormal dystrophin production prevents muscle cells from remaining intact and muscle atrophy occurs. The dystrophin gene is recessive related to X, therefore the main population reached is that of men. DMD is debilitating and affects about 300,000 men worldwide. Before the progress of modern health in respiratory and cardiac care; Patients with DMD should not survive after adolescence.

The recent release of dog genes gives hope for the treatment of DMD in humans. Researchers at the University of Texas Southwestern Medical Center are working with CRISPR technology and the DMD deltaE50-MD canine model to try to correct the DMD gene mutation. How exactly does CRISPR work? The gene editing technology uses a strand of RNA to guide Cas9 (an enzyme) in order to cut a specific part of the DNA. The logic behind the use of a canine model, especially the beagle, is that they exhibit many pathological features (muscle degeneration, weakness and fibrosis) of human DMD. Positive results from the study include CRISPR-induced restoration of the dystrophin protein in the major muscles of the body (ie the heart). The study allowed to monitor four dogs in less than two months. It is expected that the short duration and cohort of the study did not impress some scientists. However, the lead investigator, Eric Olson, responded that the fast pace of the study was to establish the ability to restore dystrophin for future research. In response to critics regarding the amount of animals used, Olson replied, "We are very concerned about ethical concerns and have done our best to keep our dog use to an absolute minimum."

The gene for dystrophin, the largest gene in humans, contains a total of 75 exons. Because of its size, there are several possibilities for mutations, but only one functional copy is needed for normal dystrophin production. A mutation that causes DMD occurs between exon 45 and exon 50, which leads to an exon 51 "out of frame" condition; prevent the production of dystrophin. The CRISPR molecular scissors used in the study were designed to perform a cut at exon 51 in beagles with DMD. It was expected that, when attempting to repair the splice, the cell would induce errors on exon 51 that would lead to a mechanism of dystrophin protein production to avoid exon. As a result of an exon jump, a shorter production (the normal protein of dystrophin has a length of 3500 amino acids) but a still functional dystrophin that has been partially restored in beagles. To help change the billions of muscle cells in dog models, the team used an adeno-associated virus (AAV) carrying the CRISPR components to infect skeletal muscles and heart tissue. The intravenous route of treatment occurred after intramuscular injections of AAV bearing CRISPR were shown to be effective in restoring dystrophin production. Two of the 1-month-old dogs received intravenous infusion of CRISPR-AAVs, resulting in dystrophin levels "up to 58% of normal in the diaphragm and 92% in the heart".

There are certainly more questions about this promotion. As the muscular damage is irreversible, the treatment will only be effective in the first years of life? Also, will CRISPR treatment induce carcinogenic mutations? Is there a way for treatment to reach stem cells? Will normal muscle function cause a shortening of dystrophin? Whatever the case may be, further exploration of CRISPR as a medical tool is essential to treat genetic diseases to improve quality of life and hope. of overall life of the patients affected.