Casδ, an evolutionary transitional CRISPR system enables efficient genome editing across animals and plants
Bibliographic record
Abstract
Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated) adaptive immune systems provide sequence-specific mechanisms for targeting foreign DNA or RNA and have been widely used in genome editing and DNA detection. Type V CRISPR-Cas systems are characterized by a single RNA-guided RuvC domain-containing effector, Cas12. Here, through comprehensive mining of large-scale genomic and metagenomic data from microbial sources, we identified a new Class 2 CRISPR-Cas effector superfamily, designated Casδ, comprising three members with protein sizes ranging from 867 to 936 amino acids. Biochemical analyses revealed that Casδ-1 functions as a single RNA-guided endonuclease with specific recognition of 5'-RYR-3' protospacer-adjacent motifs, where R represents A or G, and Y represents T or C. Casδ-1 exhibits robust double-stranded DNA cleavage activity and target-dependent trans-cleavage activity. Casδ-1 mediates efficient genome editing across species, achieving up to 60% indel rates in human cells while generating homozygous knockout lines in two agriculturally important monocot species (Oryza sativa and Zea mays) through stable transformation. Structural and evolutionary analyses reveal Casδ as an evolutionary transitional nuclease bridging Cas12n and canonical type V systems, featuring a C-terminal loop that is essential for activity. Collectively, Casδ is an evolutionarily distinct, compact (<1000 aa), tracrRNA-free CRISPR system enabling versatile cross-kingdom genome editing.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".