Genome editing has been used to demonstrate the efficacy of CRISPR-Cas to treat the genetic problem that causes cystic fibrosis. The approach adopted by the research team opens new perspectives in the treatment of the genetic disease for which no cure is currently available.

The disease is caused by a mutation of the gene that produces the cystic fibrosis transmembrane conductance regulator (Cftr), whose malfunctioning affects multiple organs, especially the lungs.

The University of Trento/KU Leuven collaborative team adapted the CRISPR-Cas system to permanently edit at least two types of the mutation that cause cystic fibrosis. The technique they used is called SpliceFix because it fixes the gene and restores the protein production mechanism at the same time.

Genomic Scalpel

Giulia Maule, doctoral student in Biomolecular sciences at the University of Trento and first author of the article, said,

“We have devised a genome editing strategy based on CRISPR-Cas to permanently remove two mutations that cause the disease. CRISPR-Cas works like a genomic scalpel to cut out the mutated elements with extreme accuracy. We demonstrated that our repair strategy works on patient-derived organoids and with a high level of precision: It targets only the mutated sequences, leaving non-mutated DNA untouched."

The researcher emphasized a novel aspect of the study:

“Instead of animal models, we have used organoids that we developed from the patients' cells, a choice that allowed us to verify the efficacy of the molecular strategy in a context that is very similar to that of the patients with cystic fibrosis."

The team developed this genome editing procedure using one of the most precise programmable nucleases, AsCas12a, and a single CRISPR RNA (crRNA).

[caption id=“attachment_99611” align=“aligncenter” width=“680”]Splicing correction in CFTR 3272-26A>G minigene model by AsCas12a editing Splicing correction in CFTR 3272-26A>G minigene model by AsCas12a editing
Credit: Giulia Maule, et al. CC-BY[/caption]

The Invisible Disease

Cystic fibrosis is also called “the invisible disease” because it has no external indicators, and yet it takes a huge toll on the lives of the people it afflicts, primarily via lung and digestive problems. The disease is inherited from parents.

In Italy, about one in 25 people is a carrier. This means that parent carriers have a one-in-four chance to conceive a child with the disease. There are about 6,000 people with cystic fibrosis in Italy, and 200 new cases every year.

The study was supported by the Italian Cystic Fibrosis Foundation, and the University of Trento.

Giulia Maule, Antonio Casini, Claudia Montagna, Anabela S. Ramalho, Kris De Boeck, Zeger Debyser, Marianne S. Carlon, Gianluca Petris & Anna Cereseto Allele specific repair of splicing mutations in cystic fibrosis through AsCas12a genome editing Nature Communications, volume 10, Article number: 3556 (2019)

Cover Image: Howard Vindin CC BY-SA 4.0

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