The CRISPR-Cas9 gene editing system, which has revolutionized genetic engineering over the last decade, involves cutting DNA strands, which is a process that can be quite difficult to control and can cause genetic changes. desired. Now, thanks to researchers at the Massachusetts Institute of Technology and the University of California, San Francisco (UCSF), a new gene editing technology called CRISPRoff may change that, according to a press release.
The technique, described in a paper published in Cell on April 9, is reversible unlike traditional CRISPY, and the changes introduced can even be transmitted to future cell lines. This non-destructive genetic editing protein acts as a simple gene shutdown switch, recreating the benefits of the widely used CRISPR-Cas9 system without damaging the genetic material of cells.
“Four years ahead [from the initial grant], and CRISPRoff finally works as intended in a science fiction way, “says Luke Gilbert, co-author.” It’s exciting to see it work so well in practice. “
“The big story here is that we now have a simple tool that can silence the vast majority of genes,” says Jonathan Weissman, who is also a professor of biology at MIT and a researcher at the Howard Hughes Medical Institute. “We can do this for several genes at once without damaging DNA, with great homogeneity and in a way that can be reversed. It’s a great tool for controlling gene expression.”
‘Genetic engineering 2.0’
In the classic CRISPR-Cas9 system, it is difficult to limit the result, which is where researchers saw the opportunity for a different gene editor.
The researchers created a small protein machine to build an epigenetic editor that could mimic the natural methylation of DNA, which is an epigenetic mechanism that occurs by adding a methyl group (CH3) to DNA. The machine, guided by small RNAs, can convert methyl groups to specific points in the chain. Methylated genes are “silenced” or turned off, hence the name of the machine.
This does not alter the sequence of the DNA strand, allowing researchers to reverse the silencing effect using enzymes that remove methyl groups. The researchers called this method CRISPRon.
The researchers found that they could use this on / off switch to target most genes in the human genome. In addition, it worked for the genes themselves, as well as for other regions of DNA that control gene expression without encoding proteins.
In addition, CRISPRoff also silenced large methylated regions called CpG islands, which was believed to be necessary for the mechanism of DNA methylation.
CRISPRoff for practical applications
The method was tested on induced pluripotent stem cells, which are cells that can be converted into other cell types in the body. When the researchers silenced a gene from the stem cells and induced them to become neurons, it was seen that the gene remained silent in 90% of the cells. This reveals that the cells retain a memory of the epigenetic modifications made by the CRISPRoff system.
In another study, researchers used the technology to silence the Tau protein, which can form groups in the brain that cause memory loss and are involved in Alzheimer’s disease in neurons. It was seen that although it was not completely off, CRISPRoff could be used to reject the Tau expression. “What we demonstrated is that this is a viable strategy to silence Tau and prevent this protein from being expressed,” says Weissman. “So the question is how to deliver it to an adult? And would it really be enough to affect Alzheimer’s? These are big open-ended questions, especially the last ones.”
Researchers are now studying new ways to apply gene editing technology. “With this new CRISPRoff technology, you can [express a protein briefly] write a program that the cell remembers and runs indefinitely, “says Gilbert.” Change the game, so now you basically write a change that is transmitted across cell divisions. Somehow, we can learn to create a version 2.0 of CRISPR-Cas9 that is more secure and effective and that can do all these other things. “