Dr Ronald Cohn, who leads the Duchenne Research Fund’s Scientific Advisory Board, has become the first ever researcher to successfully correct one of the mutations that causes Duchenne muscular dystrophy, working on cells in his laboratory at the Centre for Genetic Medicine at Toronto’s Hospital for Sick Children.
There are three main types of genetic error that can cause Duchenne. A ‘deletion’, whereby part of the code that makes up the dystrophin gene is missing; a ‘point mutation’, meaning there is an error somewhere in the code of the dystrophin gene; or a ‘duplication’, whereby part of the code of the dystrophin gene is repeated. There are also many different variations within these three broad categories.
Duplication is the rarest of the three, affecting only 12% of Duchenne patients. However, it is the mutation that has most interested the Duchenne Research Fund, as this is the error that affects Gavriel Rosenfeld, the son of our charity’s founders Kerry and Doron, and is often left unexplored.
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Working on some of Gavriel’s own cells, Dr Cohn’s team were able to effectively ‘cut out’ the duplicated part of the gene, returning the gene to its correct state. They achieved this using a revolutionary new technology called CRISPR – a gene editing technique that is more precise, efficient and cheaper than its predecessors. It acts like a genetic pair of scissors that goes in and corrects the gene. With the error removed, the cells were then able to produce normal dystrophin protein, which is essential for repairing and restoring muscles, and which boys with Duchenne lack.
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Although CRISPR has been widely used as a research tool, its potential in far-reaching therapeutic applications has largely been unexplored, explains Dr Cohn. “CRISPR is the most important technology that I have encountered in my scientific career thus far. Working with patients and families with genetic disorders, I’m often in a position where I can provide a diagnosis, and perhaps supportive care, but no treatment. CRISPR could change that. It could revolutionise the way we care for patients with currently untreatable genetic conditions.”
Accelerating this treatment into actual human beings can’t come fast enough for Dr Cohn, particularly given his close connection to Kerry, Doron and Gavriel. “I’m going to think carefully with regulatory people, ethics, industry partners. I have a whole team that is ready to sit down with me to really think through what the best and safest approach is.”