Researchers at the University of British Columbia have built a new mouse model carrying a specific patient mutation in the GRN gene, the deletion GRNc.388_391delCAGT, that causes one form of frontotemporal dementia (FTD) linked to a shortage of the protein progranulin. The work, published online June 15, 2026 in Neurobiology of Disease, was designed explicitly as a testing platform for gene therapies aimed at restoring progranulin levels, a strategy already being tried in early human trials for this same genetic cause of FTD. The mice express a mutant, humanized version of the GRN gene (called GRNmEx5) instead of the normal mouse gene, and the team reports that this mutant version is expressed at low levels but retains partial function, partially easing brain damage and gene-activity abnormalities seen when progranulin is fully absent. Using this platform, the researchers then tested a corrective approach: CRISPR/Cas9 gene editing, delivered by lipid nanoparticles, aimed at repairing the patient mutation directly in the animals' cells. They report achieving 8.5 percent correction of the mutation in target cells of these mice, a laboratory measure of how many treated cells had the deletion repaired, not a measure of any change in memory, behavior or brain pathology. The paper's authors say the model's value lies in carrying the exact deletion found in patients, allowing therapies designed to fix that specific mutation to be tested against the same genetic sequence they would ultimately need to correct in people, something earlier progranulin-deficient mouse models could not offer.