The gene editing technology CRISPR-Cas9 has been heralded as a major advance in medical research. But it has one big limitation: It doesn’t work on cells that have stopped dividing, such as neurons in the brain.
Now scientists at the Max Planck Florida Institute for Neuroscience say they’ve developed a tool that allows for precise genome editing of neurons. It capitalizes on a part of the CRISPR-Cas9 system called homology directed repair (HDR), which allows researchers to add, change or delete specific genes.
Until now, HDR has only been feasible in cells that are dividing and proliferating in the body. To correct that shortcoming, the Max Planck team combined CRISPR-Cas9 with adeno-associated virus (AAV), a mild viral vector that’s often used for gene delivery. When they delivered the combo to mouse neurons, HDR occurred in an efficient manner, they reported. When they tested it in an aged mouse model of Alzheimer’s, it also worked.
This is the latest example of research aimed at applying gene-editing technology to solving some of the toughest neurological diseases. Startup Exonics Therapeutics is also using AAV to try to correct Duchenne muscular dystrophy using a form of CRISPR. In August, researchers at the University of California in San Diego described a technique for using CRISPR to edit RNA instead of DNA—a method they believe could prove useful in finding treatments for Huntington’s and amyotrophic lateral sclerosis.
By focusing on the HDR phase of CRISPR gene editing, the Max Planck researchers believe they’ll be able to use their tool to make precise genetic changes in cells regardless of age, stage of maturity or brain region. That could accelerate research aimed at understanding normal brain processes, as well as finding therapies that work when normal functioning goes awry.