NIH‑backed miniature CRISPR Al3Cas12f achieves >80% editing efficiency in tests
- The National Institutes of Health and University of Texas at Austin researchers reported on April 13 a compact CRISPR enzyme, Al3Cas12f, engineered for stronger editing. - Their Al3Cas12f RKK variant raised editing from under 10% to above 80% across tested targets, reaching 90% at one commonly edited locus. - The work targets a delivery bottleneck: fitting editors into adeno-associated virus cargo for in-body treatment. (nih.gov)
CRISPR works like programmable molecular scissors, but many of the best cutters are too large to squeeze into the viral packages used for in-body delivery. A National Institutes of Health-backed team reported April 13 that a much smaller enzyme, Al3Cas12f, can be engineered to edit human cells far more efficiently than earlier mini-CRISPR tools. (nih.gov) (nature.com) Those viral packages are usually adeno-associated viruses, or AAVs, which can be aimed at specific tissues but can only carry instructions for proteins up to about 1,000 amino acids long. UT Austin said that size cap has helped keep many CRISPR therapies focused on cells edited outside the body, such as blood and bone marrow. (utexas.edu) (nih.gov) Cas12f enzymes are much smaller, roughly 400 to 700 amino acids, but they have generally lagged larger editors in mammalian cells. In the new Nature Structural & Molecular Biology paper, Kaoling Guan, Rodrigo Fregoso Ocampo and colleagues compared several Cas12f relatives and identified Alistipes sp. Cas12f, or Al3Cas12f, as unusually capable in human cells. (utexas.edu) (nature.com) The researchers said Al3Cas12f forms a more stable editing complex than other miniature enzymes they tested. David Taylor, a molecular biosciences professor at UT Austin and corresponding author, said the enzyme “comes preassembled and ready to go” soon after its parts are made. (nih.gov) (utexas.edu) After mapping that structure, the team engineered a variant called Al3Cas12f RKK. NIH said RKK lifted editing efficiency from less than 10% to more than 80% across tested genomic targets, and to 90% at one commonly edited region. (nih.gov) (nature.com) The tests were done in human cells, including a leukemia-derived cell line. NIH said the edited genes included targets linked to cancer, atherosclerosis and amyotrophic lateral sclerosis, the neurodegenerative disease also known as ALS. (nih.gov) The study was a collaboration between UT Austin and Metagenomi, a Bay Area biotechnology company that identified the naturally occurring enzyme through metagenomics. UT said the results were published in Nature Structural & Molecular Biology, and NIH said the work was supported in part by National Institute of General Medical Sciences grant R35GM138348. (utexas.edu) (nih.gov) The next test is whether the compact editor keeps working after it is actually packaged into AAV and sent toward tissues in the body. That is the step the team said could move this miniature CRISPR system from strong cell-line data toward therapeutic use. (nih.gov)
