Systematic deletion of every gene in the genome reveals ‘druggable’ pathways that help keep muscle cells healthy.
A new study led by Louis Kunkel, PhD, and research fellow Angela Lek, PhD at Boston Children’s Hospital used CRISPR-Cas9 to better understand facioscapulohumeral muscular dystrophy (FSHD) and explore potential treatments. FSHD causes muscle weakness in the face, shoulder blades, and upper arms, and currently has no treatment other than supportive care.
CRISPR-Cas9 gene editing technology is best known for its potential role in correcting genetic diseases. It is also used as a tool to find genes that act as supporting players, making the disease better or worse. Such genes might make good targets for new treatments.
In FSHD, the gene DUX4, normally active mainly during foetal development, is inappropriately activated. This causes toxic DUX4 protein to be produced in muscle cells when it shouldn’t be, leading to cell death and muscle weakness.
The research team then queried whether other genes could be targeted to prevent or compensate this problem. Which led them to decide on using CRISPR-Cas9 technology to systematically mutate every gene in the genome. All these were done with the goal of finding genes that when knocked out will enable human muscle cells to survive even when DUX4 protein is present.
“We essentially utilized the CRISPR screen technique as a shortcut to illuminate ‘druggable’ pathways for FSHD,” says Lek, the paper’s first author.
Through the CRISPR-Cas9 screening process they were successful in identifying several genes that play a role in the cellular response to hypoxia. Pointing out that the main driver of cell death is caused by DUX4 protein. Exposing the muscle cells to compounds known the inhibit the hypoxic process, the cells remained alive.
Going a step further, the team created muscle cell lines from actual patients with FSHD. When treated with the same compounds, these cells showed fewer of the known biomarkers of the disease.
Finally, the researchers created two live zebrafish models of FSHD. When they exposed the fish to compounds that inhibit hypoxia signalling, the fish showed improvements in muscle structure and function and more swimming activity.
“The most encouraging finding about this study is that we discovered that there are FDA-approved drugs that can overcome DUX4’s toxic effect,” says Lek. “We now have a collection of drugs to test and figure out which is most suitable for long-term dosing in patients with FSHD.”
The team has filed an application to patent their discoveries and Kunkel believes that this process used in the study can be applied to many other diseases in discovering therapeutic targets and testing potential treatments. [APBN]