2024-01-08 14:34:13
A new gene editing system, called Primewhich is capable of correcting most of the genetic mutations that cause known diseases, has just incorporated a new vehicle to introduce the corrected genes into the cells of living animals.
As explained by the researchers of the Broad Institute of MIT and Harvard (USA) in a study published in ‘Nature Biotechnology‘, involves using virus-like particles to deliver gene editors into mouse cells. The results show that this new technology has managed to partially restore vision in mice.
The team has used their new system to correct disease-causing mutations in the eyes of two mouse models of genetic blindness.
«The study is the first in which the administration of protein-RNA complexes has been used to achieve therapeutic primary editing in an animal,” he says. David Liu lead author of the study.
Gene editing approaches promise to treat a variety of diseases by precisely correcting disease-causing genetic mutations.
The primary editing technique, described in 2019 by Liu’s group, allows for longer and more diverse changes to DNA than other types of editing. However, translating the complex gene editing machinery into the cells of living animals has been a challenge.
The main editing system has three components: a Cas9 protein that can cut DNA; a designed master editing guide RNA (pegRNA) that specifies the location of the edit and also contains the new edited sequence to install at that location; and a reverse transcriptase that uses the pegRNA as a template to make specific changes to the DNA.
Researchers have used various methods to deliver this molecular machinery to cells, including viruses and lipid nanoparticles. One of them has been virus-like particles (VLPs), composed of a layer of viral proteins that carry cargo but lack viral genetic material. But VLPs have traditionally produced modest results in animals and must be specifically designed so that each different type of cargo is efficiently delivered to cells.
In the new work, the researchers redesigned both the eVLP proteins and the primary editing machinery itself so that both the delivery and editing systems worked more efficiently.
While each individual improvement generated small increases in the efficiency of core editors, the changes together had a much larger impact.
100 times more powerful
“When we combined everything, we saw improvements of approximately 100 times compared to the eVLPs we started with – explains Liu -. “That kind of efficiency improvement should be enough to give us therapeutically relevant levels of core editing, but we didn’t know for sure until we tested it in animals.”
The team first tested the system in mice to correct two different genetic mutations in the eyes. A mutation, in the Mfrp gene, causes a disease called retinitis pigmentosa leading to progressive retinal degeneration. The other, in the Rpe65 gene, is associated with the blindness seen in the condition known as Leber congenital amaurosis (LCA) in humans.
In both cases, the eVLPs corrected the mutation in up to 20% of the animals’ retinal cells, partially restoring their vision.
The group also showed that eVLPs loaded with core editing machinery could effectively edit genes in the brains of living mice. Almost half of all cells in the cerebral cortex that received the editing machinery showed gene editing.
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