Two New CRISPR Developments: A Smaller, Sharper Tool and a Tumor-Targeting Cutter
Recent research has unveiled two significant advances in CRISPR gene editing technology. One team has engineered a more efficient, compact nuclease suitable for in-body delivery, while another has developed a method to selectively target tumor DNA by exploiting its unique chemical signatures.
Development of a Smaller, Higher-Efficiency CRISPR Nuclease (Al3Cas12f RKK)
A team from the University of Texas at Austin, in partnership with Metagenomi Therapeutics, has engineered a smaller, more efficient CRISPR nuclease variant. The findings, published in Nature Structural & Molecular Biology, aim to overcome a major hurdle for in-body gene therapy: the size of the delivery vehicle.
The Challenge
Current clinical applications often involve editing cells outside the body because many effective gene-editing enzymes are too large for common delivery vectors. Adeno-associated virus (AAV) vectors, which can deliver genetic instructions to specific cells, have a packaging limit of roughly 1,000 amino acids. Smaller nucleases from the Cas12f family (400-700 amino acids) were promising but had shown limited editing efficiency in human cells.
The Innovation
The research focused on a naturally occurring bacterial nuclease, Al3Cas12f, identified by Metagenomi. Using cryo-electron microscopy and machine learning, the team analyzed its structure and discovered an expanded interface between its components that contributes to stability.
They modified this enzyme to create an engineered variant named Al3Cas12f RKK. The results were dramatic:
The original Al3Cas12f achieved less than 10% editing efficiency. The engineered variant, Al3Cas12f RKK, achieved more than 80% efficiency.
The genes targeted for editing are linked to conditions including cancer, atherosclerosis, and amyotrophic lateral sclerosis (ALS). The study reported that Al3Cas12f demonstrated higher efficiency than two other Cas12f enzymes recently used in mouse studies.
Next Steps
The researchers plan to test the Al3Cas12f RKK nuclease's performance when packaged into AAV vectors.
Development of a CRISPR Variant for Tumor DNA Targeting (ThermoCas9)
In a separate study published in Nature on April 15, 2026, a research team from Wageningen University & Research and the Van Andel Institute has developed a method to selectively cut DNA in tumor cells while leaving healthy cells intact.
The Mechanism
This method is the first reported instance of a CRISPR-based approach using DNA methylation patterns to target human cancer cells. DNA methylation, a chemical modification that regulates gene expression, is often altered in cancer.
The technique relies on a CRISPR variant called ThermoCas9. The enzyme must first attach to a specific recognition sequence (a PAM, or Protospacer Adjacent Motif) adjacent to its DNA target.
- Normal operation: ThermoCas9 binds to its PAM sequence and cuts the DNA.
- Selective inhibition: When a methyl group is present at a specific site within the PAM sequence, it physically prevents ThermoCas9 from binding.
- The result: In lab experiments on human cells, this mechanism allowed ThermoCas9 to selectively cut DNA in tumor cells (which have different methylation patterns) while leaving healthy cells intact.
Research Status
The study demonstrated selective DNA cleavage but did not show that this effect leads to tumor cell death. The next step for researchers is to investigate whether damaging tumor DNA with this method can trigger cell death. The technology is described as an early-stage finding requiring further development.
Authors & Funding
- ThermoCas9 Co-first authors: Mitchell O. Roth, Yuerong Shu, Yu Zhao, Renee D. Hoffman (Van Andel Institute); Despoina Trasanidou (Wageningen University).
- ThermoCas9 Funding: The research was supported by the National Institutes of Health, the Dutch Research Council, the European Research Council, University Fund Wageningen, and the Dutch Ministry of Economic Affairs.