Programmable large-fragment genome integration using prime-editing-coupled serine integrases, such as PASTE and PASSIGE, remains constrained by the limited activity of wild-type Bxb1 (WT Bxb1) in mammalian cells. Recently, the AI-guided protein engineering framework EVOLVEpro enabled efficient identification of functional protein variants from limited experimental sampling and nominated epBxb1(T166R) as a highly active Bxb1 variant in episomal plasmid-to-plasmid recombination screens. Here, we systematically benchmarked epBxb1 (T166R) against WT Bxb1 and the previously validated high-activity eeBxb1 (V74A/E229K/V375I) variant in genome-integrated reporter and endogenous-locus PASSIGE assays at three well-characterized benchmarking loci ( AAVS1 , CCR5 , and ACTB ). epBxb1 showed reduced and variable transferability, with no detectable advantage over WT Bxb1 in the genome-integrated reporter system or at the AAVS1 safe-harbor locus, but produced modest, locus-dependent improvements at CCR5 and ACTB , with 1.89-fold and 1.58-fold increases, respectively. By contrast, eeBxb1 consistently showed superior activity, achieving up to ∼12-fold improvement over WT Bxb1. Four additional rounds of EVOLVEpro-guided optimization on the eeBxb1-BPNLS scaffold identified no reproducibly improved variant among 40 tested single-amino-acid substitutions. These results indicate reduced and genomic context-dependent transferability of EVOLVEpro-nominated Bxb1 variants and highlight the importance of application-matched genomic benchmarking when implementing AI-guided protein optimization for therapeutic genome writing.
Dog allergy is a prevalent IgE-mediated condition, with the salivary lipocalin Can f 1 accounting for the majority of dog-specific IgE reactivity in sensitized individuals. Existing strategies for managing dog allergy primarily rely on modulating host immune responses and do not address allergen production at its source. Here, we report the generation of genetically engineered dogs lacking Can f 1. Using CRISPR-Cas9 editing and somatic cell nuclear transfer, we produced two healthy beagle puppies carrying a frameshift mutation in exon 1 of the Can f 1 gene. Salivary and hair/dander analysis demonstrated the absence of Can f 1 protein in the edited dogs. Skin prick testing in a sensitized individual demonstrated robust IgE-mediated reactivity to control dog extracts but no detectable response to extracts from the edited dogs. Together, these findings demonstrate that targeted genetic knockout of the major dog allergen is compatible with canine development and can abolish the IgE-mediated allergic response, supporting the feasibility of a gene-based approach to reducing canine allergenicity.
CRISPR interference (CRISPRi) often uses single guide RNAs (sgRNAs) generated by in vitro transcription (IVT); however, IVT-derived RNAs can trigger innate immune responses that confound functional analyses. Here, we evaluate innate immune activation induced by IVT sgRNAs in a CRISPRi setting and show that enzymatic removal of the 5'-triphosphate group alone is insufficient to consistently eliminate this response. We therefore assessed modifications of IVT reaction conditions and found that supplementation with sodium chloride or urea further attenuated immune activation. Based on immune suppression, sgRNA yield, and knockdown efficiency, 0.15 M NaCl was selected for the optimized IVT condition. This condition showed a lower double-stranded RNA (dsRNA) concentration, providing direct support for reduced dsRNA by-products as a contributor to diminished immune activation. By integrating NaCl-supplemented IVT with phosphatase treatment, we establish an optimized and scalable workflow that minimizes innate immune responses while preserving sgRNA-mediated target knockdown efficiency in stable CRISPRi cells.
Since the advent of Cas9-based CRISPR technologies in 2012, there has been a remarkable growth in genome editing research, literature, applications, and translational impact. Much of this research has been fueled by the global dissemination of CRISPR plasmids through nonprofit distribution by Addgene, as both a repository and distributor of enabling biological material. Recently, key milestones have been reached, with over 20,000 plasmids deposited by over 1,000 labs, being distributed over 300,000 times globally. The driving trends reflect multidimensional diversification in terms of effectors (Cas9, Cas12 and beyond), editing modalities (base editing, prime editing, epigenetic modification, CRISPRi/a), and deployment across phylogenetic groups (mammalian, bacterial, plant, yeast, insects, and more). Noteworthy, guide RNA and HDR templates account for the bulk of deposits, while cloning backbones are the most requested, and lentiviral plasmids comprise the majority of expression material. The data reflect a continued diversification of the CRISPR-based toolbox, robust interest in genome editing applications across the tree of life, maturation in terms of adoption, and rising relative distribution beyond the USA and China, with Addgene continuing to play a critical role in access to equitable and disruptive technologies.
