Gene-editing tool can programme cuts over time

New process uses special molecules called ‘proGuides’ to improve CRISPR gene editing.

Researchers from the University of Illinois Chicago have discovered a new gene-editing technique that allows sequential cuts – or edits – to be programmed over time.

Longevity.Technology: “Gene therapy is now in its golden age,” as genome editors “open even more avenues for treating disease.” So said the President of the American Society of Gene and Cell Therapy, Guangping Gao, PhD, last year. With a way to use CRISPR in an intelligent, sequential process now on the cards, mainstream genetic longevity therapy seems a step closer.

CRISPR is a gene-editing tool that allows scientists to change the DNA sequences in cells, often adding a desired sequence of bases or swapping in genes. CRISPR uses an enzyme called Cas9 that acts like tiny scissors, snipping DNA at precise location. Once a cut is made, the ways in which cells’ own machinery repair the DNA break can be influenced to result in different changes or edits to the DNA sequence.

Since the gene-editing capabilities of the CRISPR system were documented in the early 2010s, the process of guiding CRISPR to target almost any DNA sequence in a cell or to target many different sites in a cell in a single experiment has become very popular, with several variations, such as prime editing, now also available.

“A drawback of currently available CRISPR-based editing systems is that all the edits or cuts are made all at once. There is no way to guide them so that they take place in a sequential fashion, one after the other,” said UIC’s Bradley Merrill, associate professor of biochemistry and molecular genetics at the College of Medicine and lead author of the paper [1].

“The ability to pre-program the sequential activation of Cas9 at multiple sites introduces a new tool for biological research and genetic engineering …”

The Chicago research team’s new process involves the use of special molecules called guide RNA; their role is to transport Cas9 enzyme within the cell and to determine the precise DNA sequence at which Cas9 will make its cut. The researchers call their specially-engineered guide RNA molecules “proGuides,” and the molecules allow for the programmed sequential editing of DNA using Cas9 [2].

Although proGuide is still in the prototype phase, Merrill and colleagues plan to further develop their concept and are hopeful that other researchers will be able to use the technique shortly.

“The ability to pre-program the sequential activation of Cas9 at multiple sites introduces a new tool for biological research and genetic engineering,” Merrill said. “The time factor is a critical component of human development and also disease progression, but current methods to genetically investigate these processes don’t work effectively with the time element.

Our system allows for gene editing in a pre-programmed fashion, enabling researchers to better investigate time-sensitive processes like how cancer develops from a few gene mutations and how the order in which those mutations occur may affect the disease [1].”