Researchers Use CRISPR/Cas to Repair Two Mutations of the Cystic Fibrosis Gene

cystic fibrosis
The researchers cultivated organoids which they harvested from biopsies of cystic fibrosis patients. These organoids are mini intestines with the cystic fibrosis gene, as it were. | © KU Leuven (recorder by Indra Van Zundert)

Biomedical scientists at KU Leuven and the University of Trento have used gene correction to fix two mutations that cause cystic fibrosis. The breakthrough involved a petri dish with 3D cell structures, or organoids, from cystic fibrosis patients. The results were published in the journal Nature Communications.

Cystic fibrosis is the most common genetic disorder in Belgium. Children and young adults with cystic fibrosis mostly suffer from respiratory and digestive problems. The disease is caused by mutations in the CFTR gene, which contains the code for an ion channel in the lungs and intestines. An ion channel is a microscopically small sluice in the wall of the cell that allows charged particles to flow in and out. The particles in question are chloride and bicarbonate: if these cannot get to the lungs and intestines in high enough quantities to hydrate the mucus, you get a thick mucus that is no longer able to kill bacteria efficiently.

Various treatments exist to fight cystic fibrosis, including the correction of the cystic fibrosis gene. A research team of the University of Trento in Italy, led by doctor Anna Cereseto, has been working on “molecular scissors” for many years. These “scissors” are known as the CRISPR/Cas technique to snip and edit DNA. The Italian researchers have designed CRISPR/Cas scissors for two specific mutations of the CFTR gene.

At KU Leuven, first author Giulia Maule and Dr Marianne Carlon at the Molecular Virology and Gene Therapy group (led by Professor Zeger Debyser) then inserted the two scissors in the cells of patients suffering from cystic fibrosis.

Giulia Maule explains: “We cultivated organoids – three-dimensional cell structures – that we harvested from intestine biopsies of cystic fibrosis patients. These organoids are mini intestines with the cystic fibrosis gene, as it were.”

“Next, we developed a way to insert the CRISPR/Cas scissor in the cells using gene-stripped viruses that can enter the cells with the treatment material in them. The combination of these techniques allowed us to repair the genetic defect: we were able to restore the flow of chloride particles. This can be easily verified, as the mini intestines start to bloat: the channels open and let the chloride particles flow through. These, in turn, attract water to the inside of the organoids.”

This technique doesn’t only enable us to correct mutations in cystic fibrosis patients, but also opens up new perspectives for other genetic disorders.

Doctor Marianne Carlon, coordinator of the organoid research in Leuven, underlines the importance of the new approach: “This technique requires the utmost precision. It’s encouraging to see it work because it doesn’t only enable us to correct mutations in cystic fibrosis patients, but also opens up new perspectives for other genetic disorders. However, we do need to conduct a lot more research to be able to move from a petri dish with organoids to a patient in the hospital.”