Correcting half the faulty heart muscle cells in mouse model of FA completely reverses cardiomyopathy People with Friedreich’s ataxia (FA) often develop cardiac symptoms, including changes to the heart muscle, known as cardiomyopathy. A potential way to treat the heart symptoms in FA is to deliver the correct frataxin gene to the cells in the heart. Researchers have recently investigated the use of ‘adeno-associated virus-mediated’ gene therapy (or AAV for short) to explore this issue. It works by using a viral ‘vector’ (a virus combined with a therapeutic gene) to insert genetic material into cells of the body. In a previous study, AAV gene therapy was shown to fully reverse the heart problems present in a mouse model of FA. At the dose used in this study almost all of the faulty heart muscle cells were corrected. These results, however, are likely to be difficult to replicate in a clinical trial as the equivalent dose of vector used in the mouse model was much higher than the amount that would usually be given to humans. Researchers in the present study have therefore attempted to establish the minimum amount of vector that could be used in order to have a therapeutic effect. They discovered that actually only half of the faulty heart muscle cells needed to be corrected in order to fully reverse the heart problems in the mouse model. In addition, a meaningful therapeutic effect could be achieved with as little as 30% of the heart muscle cells being corrected, regardless of how severe the heart problems were. This study lays the foundation for the development of a gene therapy to treat the heart problems present in patients with FA.