A new approach to genome editing

LA JOLLA, Calif.—When anyone mentions gene editing these days, the first thing to come to mind is likely CRISPR/Cas9, the reigning champ in terms of editing DNA. While other Cas proteins have been identified with encouraging characteristics—more specificity, the ability to target DNA and RNA, etc.—CRISPR/Cas9 is still the basic standard.

 

But it might be gaining some competition—and not from another Cas protein, but from a different editing technology entirely. A team from Salk Institute has unveiled a new editing tool that has proved capable of targeting a variety of mutations and cell types: SATI.

 

SATI stands for intercellular linearized Single homology Arm donor mediated intron-Targeting Integration. SATI is a gene knock-in method, and builds on previous work out of the lab of Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory and senior author of the paper detailing this latest work. The lab has work with CRISPR/Cas9-based gene editing before with HITI (homology-independent targeted integration), which they developed and which can target dividing and non-dividing cells.

 

SATI builds off of the HITI approach. A key benefit of SATI is that it can target non-coding regions of the DNA. As these regions comprise roughly 98 percent of our DNA and regulate cell functions such as switching genes on and off, it opens up a lot of possibilities. SATI inserts a normal copy of a problematic gene into the non-coding region of the DNA before the sit of the mutation in the original gene. As a result, the new copy of the gene is integrated into the genome along with the old gene thanks to a DNA repair pathway, which ameliorates the issues linked to the original mutated copy without the damage risk of replacing it entirely.

 

“We sought to create a versatile tool to target these non-coding regions of the DNA, which would not affect the function of the gene, and enable the targeting of a broad range of mutations and cell types,” says Mako Yamamoto, co-first author on the paper and a postdoctoral fellow in the Izpisua Belmonte lab. “As a proof of concept, we focused on a mouse model of premature aging caused by a mutation that is difficult to repair using existing genome-editing tools.”

 

Specifically, the team worked with mouse models of progeria, a premature-aging disease caused by a mutation in the LMNA gene, which leads to a buildup of the protein progerin. SATI was used to insert a normal copy of LMNA into the mice, which successfully established proof of concept. The mice presented with diminished signs of aging in several tissues, such as the skin and spleen, as well as a 45-percent increase in life span compared to untreated progeria mice. A Salk Institute press release notes that “A similar extension of life span, when translated to humans, would be more than a decade.”

 

The next step is to make SATI more efficient to ensure that more cells incorporate the new, adjusted DNA.

 

“This study has shown that SATI is a powerful tool for genome editing,” noted Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory and senior author of the paper. “It could prove instrumental in developing effective strategies for target-gene replacement of many different types of mutations, and opens the door for using genome-editing tools to possibly cure a broad range of genetic diseases.”

 

This work, published in the paper “Precise in vivo genome editing via single homology arm donor mediated intron-targeting gene integration for genetic disease correction,” appeared in Cell Research.

 

 

SOURCE: Salk Institute press release