CRISPR-Cas9 editing involves cutting DNA strands, leading to permanent changes to the cell's genetic material. ...uses a DNA-cutting protein called Cas9 found in bacterial immune systems. The system can be targeted to specific genes in human cells using a single guide RNA, where the Cas9 proteins create tiny breaks in the DNA strand. Then the cell's existing repair machinery patches up the holes. That's where the researchers saw an opportunity for a different kind of gene editor—one that didn't alter the DNA sequences themselves, but changed the way they were read in the cell. Epigenetic gene silencing often works through...