Energy Boost

In CRISPR gene editing, a short stretch of RNA (called a guide RNA) directs the DNA-cutting enzyme Cas9 to chop up a particular genetic sequence. But guide RNAs can also be used to direct transcriptional regulatory proteins to specific sequences – by fusing the proteins with enzymatically inactive Cas9. This enables the alteration of a gene’s expression without damaging the DNA sequence. In the human heart cells pictured, for example, transcriptional activation factors fused to inactive Cas9 have been used to boost production of a master mitochondrial regulatory protein (red) and, consequently, mitochondria themselves (yellow). This approach (known as CRISPRa) was shown to ramp up mitochondrial energy production in heart muscle samples from heart failure patients. It also improved heart function after a myocardial infarction (heart attack) in model mice. Together the results pave the way for clinical development of CRISPRa for not only heart failure but other mitochondrial dysfunction disorders too.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image courtesy of Saad Malik and Mario Escobar
• Department of Bioengineering, Rice University; Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX, USA
• Image copyright held by the original authors
• Research published in Molecular Therapy, March 2026