Gene editing techniques like CRISPR Cas9, while revolutionary and game-changing, have their limitations. One of this is the inability to target stable, non-dividng cells in the eyes, brain, heart, kidneys and liver.
But a new study published in Nature is changing that. Researchers from the Salk Institute have demonstrated the ability to edit the DNA of cells that do not divide or modify their DNA, partially restoring sight in mice born with genetic defects.
Their study involved targeting NHEJ, a DNA-repair cellular pathway present in most cells. Damaged DNA is repaired by rejoining the original strand ends. The researchers set to work modifying the NHEJ pathway to accommodate the CRISPR Cas9 gene editing technique.
They used a custom insertion package called HITI (homology-independent targeted integration) to deliver genetic instructions to the target. All this allowed the researchers to place DNA in cells not previously responsive to CRISPR, making them candidates for gene editing.
To test their method, they decided to cure mice’s retinitis pigmentosa. This is an inherited disorder caused by a faulty gene that makes retinal cells die off. One of these faulty genes is Mertk. So the scientists inserted a replacement Mertk in 3-week old partially blind mice. At the 8 week mark, the rodents showed signs of responsiveness to light.
If proven and perfected, the procedure could usher in a new milestone in genetic engineering. Previous gene editing efforts focused on embryonic stem cells, since they have the propensity to divide a lot. With these, genetic aberrations in a regular adult could be corrected.
The researchers are already at work improving the method. They want to increase the efficacy rate from a mere 5% of cells responding to something closer to 100%.
The company wants to look into gene therapies for muscular dystrophy, hemophilia and cystic fibrosis. They estimate that the product could begin human clinical trials in one to five years.