The Belmonte lab's advanced in vivo Cas9-based epigenetic gene activation system enhances skeletal muscle mass and fiber size growth in a treated mouse (right) compared with an independent control (left). The fluorescent microscopy images show purple staining of the laminin glycoprotein in tibialis anterior muscle fibers. (Credit: Salk Institute)

Soon, we might not just be editing DNA itself, but how and when the genes it encodes are expressed. In a paper published Thursday in the journal Cell, scientists from the Salk Institute report using the gene-editing tool CRISPR in mice to alleviate symptoms of type 1 diabetes and Duchenne muscular dystrophy, without making edits to the actual genome. Instead, they used CRISPR to turn the genes on and off.

Why it matters: Genetic editing to treat disease raises questions about the ethics of permanently changing someone’s DNA. These edits are reversible. CRISPR also involves cutting both strands of DNA, which some scientists are concerned could lead to unexpected and unwanted mutations. By altering the expression of genes rather than the genetic material itself, researchers hope to avoid these potential problems and treat diseases that aren't caused by genetic mutations.

Sound smart: Epigenetics is the study of how our genes are regulated. Every cell in our body contains the same DNA, but those cells behave differently depending on which genes are turned on or off. That happens when molecules attach to them and prevent the genetic blueprint from being read. These changes are involved in a host of diseases, including some cancers, but also allow us to adjust to our environment without editing our actual genetic material. Scientists hope to harness this power to treat illnesses.

What they did: To treat type 1 diabetes, the researchers used CRISPR to convince liver cells to behave like a pancreas and produce insulin. For Duchenne muscular dystrophy, which causes muscle wasting, they turned on genes that code for follistatin, a protein that codes muscles.

Yes, but: This technique isn’t for every disease, study authors Hsin-Kai (Ken) Liao and Fumiyuki Hatanaka tell Axios. It can’t correct diseases caused by mutations, for example — something that many scientists hope CRISPR gene editing will be able to do. But it can also treat some diseases that traditional gene editing cannot.

What’s next: This study didn’t look to see if the technique was safe — just if it worked. Liao and Hatanaka say they need to make sure the body’s immune system doesn’t attack the CRISPR system being used.

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