CRISPR Journal最新文献

Several type II Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 RNA-guided nucleases are commonly used for genome engineering. Their relatively large size and requirements for specific protospacer adjacent motif (PAM) sequences flanking their targets prompt continuous searches for additional more compact Cas9 enzymes with new PAM specificities. Here, we present SuCas9, a compact nuclease from Streptococcus uberis, a bacterium inhabiting the mammary glands of dairy cattle. SuCas9 recognizes a novel 5'-NNAAA-3' PAM, efficiently cleaves DNA in vitro, and is active in human cells. SuCas9 thus expands the available genome editing toolset and may find biotechnological and medicinal applications in the future.

The utility of human pluripotent stem cells (hPSCs) is greatly enhanced by the ability to introduce precise, site-specific genetic modifications with minimal off-target effects. Although Cas9 endonuclease is an exceptionally efficient gene-editing tool, its propensity for generating biallelic modifications often limits its capacity for introducing heterozygous variants. Here, we use prime editing (PE) to install heterozygous edits in over 10 distinct genetic loci, achieving knock-in efficiencies of up to 40% without the need for subsequent purification or drug selection steps. Moreover, PE enables the precise introduction of heterozygous edits in paralogous genes that are otherwise extremely challenging to achieve using endonuclease-based editing approaches. We also show that PE can be successfully combined with reprogramming to derive heterozygous induced pluripotent stem cell clones directly from human fibroblasts and peripheral blood mononuclear cells. Our findings highlight the utility of PE for generating hPSCs with complex edits and represent a powerful platform for modeling disease-associated dominant mutations and gene-dosage effects in an entirely isogenic context.

Modern gene synthesis platforms enable investigations of protein function and genome biology at an unprecedented scale. Yet, the proportion of error-free constructs in diverse gene libraries decreases with length due to the propagation of oligo synthesis errors. To rescue these error-free constructs, we developed Barcode-Assisted Retrieval CRISPR-Activated Targeting (BAR-CAT), an in vitro method that uses multiplexed dCas9-single-guide RNA (sgRNA) complexes to extract barcodes corresponding to error-free constructs. After a 15-min incubation and wash regimen, three low-bundance targets in a 300,000-member test library were enriched 600-fold, greatly reducing downstream requirements. When applied to a 384-gene DropSynth gene library, BAR-CAT enriched 12 targets up to 122-fold and revealed practical limits imposed by sgRNA competition and library complexity, which now guide ongoing protocol scaling. By eliminating laborious clone-by-clone validation and working directly on plasmid libraries, BAR-CAT provides a platform for recovering perfect synthetic genes, subsetting large libraries, and ultimately lowering the cost of functional genomics at scale.

CRISPR-Cas9 genome editing offers significant opportunities to improve livestock traits; however, its application in buffalo has been very limited, with no prior reports of live gene-edited animals. Here, we report the successful birth of a buffalo edited in the myostatin (MSTN) gene. To achieve this, five single-guide RNAs (sgRNAs) targeting the buffalo MSTN gene were designed and tested in skin-derived fibroblasts. Among these, sgRNA5 exhibited the highest editing efficiency, approaching ∼50%, as confirmed by T7 Endonuclease I assay, Tracking of Indels by Decomposition, and Inference of CRISPR Edits analyses. Single-cell cloning identified six edited fibroblast clonal populations, including one with a bi-allelic frameshift mutation predicted to severely truncate the MSTN protein. These bi-allelic clonal cells were subsequently used as nuclear donors to produce somatic cell nuclear transfer (SCNT) embryos, which were transferred into recipient buffaloes (n = 15). This effort established three pregnancies and resulted in the birth of one live MSTN knockout buffalo calf. Phenotypically, the calf displayed accelerated growth and increased muscle fiber number and size while maintaining normal meat composition. In conclusion, this study reports the world's first gene-edited buffalo generated through CRISPR-Cas9-mediated genome editing combined with SCNT. These findings provide a proof-of-concept for genome editing in buffalo and demonstrate that MSTN disruption can effectively enhance muscle growth and meat production traits.

The tuberous sclerosis complex (TSC)2 gene regulates the mammalian target of rapamycin (mTOR) pathway, impacting cell proliferation and growth. The loss-of-function mutations, especially in mesenchymal progenitors, drive the development multiple benign and malignant tumors. TSC2 mutations in certain cancer types, e.g., breast cancer, are also associated with poorer prognosis. The databases of TSC2-mutations report point mutations as the most prevalent. We aimed to test the feasibility of inducing point mutations in mesenchymal stem cells (MSCs), targeting the most frequent point mutations of the TSC2 gene, TSC2. c.1864 C>T (p.Arg622Trp), TSC2. c.1832 G>A (p.Arg611Glu), and TSC2. c.5024 C>T (p.Pro1675Leu) using two delivery methods for CRISPR-Cas9. We report a high editing efficiency of up to 85% inducing TSC2 point mutations in hMSCs using lipofectamine-based transfection. Overall, the high editing efficiency of some TSC2 mutations enables the induction and reversal of mutations in primary hMSCs without needing resource-consuming derivation of cell lines frequently distinct from their primary counterparts.

Prime editing is a clustered regularly interspaced short palindromic repeats-based approach that enables the introduction of precise genetic modifications, including missense mutations, making it valuable for generating disease models. The comparative performance of novel prime editor (PE) variants in zebrafish remains largely unexplored. Here, we systematically evaluated the efficiency of five PEs-PE2, PE6b, PE6c, PEmax, and PE7-in zebrafish. We tested mRNA encoding for each of these PEs with prime editing guide RNAs (pegRNAs) designed to install five missense mutations. Efficient editing was achieved at four of the five sites with multiple PEs. Among these, PEmax emerged as the most efficient editor for introducing pure prime edits, with rates reaching 15.34%. We found that strategies proposed to block 3' degradation of pegRNAs (epegRNAs and addition of a La RNA binding motif to the PE) did not improve performance in our assays. Together, these findings establish PEmax as a robust tool to introduce missense mutations into zebrafish.