Detection of Marker-Free Precision Genome Editing and Genetic Variation through the Capture of Genomic Signatures

Quantification of Cry1Ab protein in genetically modified plants based on immunoaffinity magnetic bead enrichment and high-performance liquid chromatography-tandem mass spectrometry

Quantification of Cry1Ab in genetically modified (GM) plants based on immunoaffinity magnetic bead enrichment and high-performance liquid chromatography-tandem mass spectrometry was developed. The active concentration of Cry1Ab standard solution was determined via surface plasmon resonance. Magnetic beads coated with Cry1Ab monoclonal antibodies were used for affinity enrichment of the target protein from samples. After trypsin digestion, quantification was performed by LC-MS/MS with internal standards, showing the recovery rate of (93.2 %-110.69 %) and relative standard deviation of (2.4 %-4.8 %, n = 12). The limit of detection was 5.7 ng/mL, and the limit of quantification was 22.5 ng/mL. The method was further validated by comparing the measured Cry1Ab concentrations in GM soybean and corn leaves with those obtained using ELISA. This method enables facilitating accurate quantitation of Cry1Ab and the assessment of environmental impact, pest control efficacy, and safety of GM crops.

CHD6 has poly(ADP-ribose)- and DNA-binding domains and regulates PARP1/2-trapping inhibitor sensitivity via abasic site repair

To tolerate oxidative stress, cells enable DNA repair responses often sensitive to poly(ADP-ribose) (PAR) polymerase 1 and 2 (PARP1/2) inhibition-an intervention effective against cancers lacking BRCA1/2. Here, we demonstrate that mutating the CHD6 chromatin remodeler sensitizes cells to PARP1/2 inhibitors in a manner distinct from BRCA1, and that CHD6 recruitment to DNA damage requires cooperation between PAR- and DNA-binding domains essential for nucleosome sliding activity. CHD6 displays direct PAR-binding, interacts with PARP-1 and other PAR-associated proteins, and combined DNA- and PAR-binding loss eliminates CHD6 relocalization to DNA damage. While CHD6 loss does not impair RAD51 foci formation or DNA double-strand break repair, it causes sensitivity to replication stress, and PARP1/2-trapping or Pol ζ inhibitor-induced γH2AX foci accumulation in S-phase. DNA repair pathway screening reveals that CHD6 loss elicits insufficiency in apurinic-apyrimidinic endonuclease (APEX1) activity and genomic abasic site accumulation. We reveal APEX1-linked roles for CHD6 important for understanding PARP1/2-trapping inhibitor sensitivity.

Do not overlook the possibility of genome-edited somatic cells ending up in the human germline

Most debates on human germline genome editing have limited discussions to just genetic modifications of sperm and eggs (gametes), their precursors within testicular or ovarian tissues, and preimplantation human embryos. What has largely been overlooked is that genome editing of somatic (non-reproductive) cells can also become heritable and can potentially be transmitted to future generations of human offspring under specific experimental conditions, due to the emergence of various new technology platforms. Most notably, the reprogramming of human somatic cells to a pluripotent "embryonic stem cell-like" state (i.e. induced pluripotent stem cells), has opened up the possibility that genome editing performed on human somatic cells can also be transmitted to future generations of human offspring when combined with other new technology platforms, such as in vitro gametogenesis, chimeric and synthetic embryos. Additionally, due to high levels of plasticity and extensive tissue remodeling within the human fetus during gestation, it is speculated that genome editing performed on fetal somatic cells intended for fetal gene therapy in utero may be unintentionally transmitted to the human germline. Hence, there should be strict regulatory oversight to ensure that any genome-edited somatic cell that ends up in the human germline via such aforementioned technology platforms does so in strict compliance with relevant legislation and ethical guidelines, especially that pertaining to safety issues with genome editing technology and its potential misuse in human enhancement and eugenics.

A protocol for the detection of precision genome editing in human cells using One-pot DTECT

Prime editing is a highly versatile CRISPR-based genome editing technology that allows for the precise installation of desired genetic variants. This protocol describes how to use One-pot DTECT to assess prime editing efficiency in human cells. Key steps include conducting prime editing, extracting genomic DNA, performing AcuI-tagging PCR, capturing genetic signatures, and detecting captured signatures through qualitative, quantitative, and visual methods. One-pot DTECT enables same-day detection of targeted genetic signatures introduced by precision genome editing technologies using off-the-shelf reagents. For complete details on the use and execution of this protocol, please refer to Baudrier et al.1.

One-pot DTECT enables rapid and efficient capture of genetic signatures for precision genome editing and clinical diagnostics

The detection of genomic sequences and their alterations is crucial for basic research and clinical diagnostics. However, current methodologies are costly and time-consuming and require outsourcing sample preparation, processing, and analysis to genomic companies. Here, we establish One-pot DTECT, a platform that expedites the detection of genetic signatures, only requiring a short incubation of a PCR product in an optimized one-pot mixture. One-pot DTECT enables qualitative, quantitative, and visual detection of biologically relevant variants, such as cancer mutations, and nucleotide changes introduced by prime editing and base editing into cancer cells and human primary T cells. Notably, One-pot DTECT achieves quantification accuracy for targeted genetic signatures comparable with Sanger and next-generation sequencing. Furthermore, its effectiveness as a diagnostic platform is demonstrated by successfully detecting sickle cell variants in blood and saliva samples. Altogether, One-pot DTECT offers an efficient, versatile, adaptable, and cost-effective alternative to traditional methods for detecting genomic signatures.

Current advancement in the application of prime editing

Prime editing (PE) is a precise genome manipulation technology based on the "search and replace" approach of the CRISPR-Cas9 system, while it does not require the exogenous donor DNA and the DNA double-strand breaks (DSBs). Comparing the base editing technology, the editing scope of prime editing has been widely expanded. Prime editing has been successfully applied in a variety of plant cells, animal cells and the model microorganism Escherichia coli so far, and it has shown a good application potential in breeding and genomic functional study of animals and plants, disease treatment, and modification of the microbial strains. In this paper, the basic strategies of prime editing are briefly described, and its research progress is summarized and prospected from the application of multiple species. In addition, a variety of optimization strategies for improving its efficiency and specificity of prime editing are outlined.

CRISPR-based genome editing through the lens of DNA repair

Genome editing technologies operate by inducing site-specific DNA perturbations that are resolved by cellular DNA repair pathways. Products of genome editors include DNA breaks generated by CRISPR-associated nucleases, base modifications induced by base editors, DNA flaps created by prime editors, and integration intermediates formed by site-specific recombinases and transposases associated with CRISPR systems. Here, we discuss the cellular processes that repair CRISPR-generated DNA lesions and describe strategies to obtain desirable genomic changes through modulation of DNA repair pathways. Advances in our understanding of the DNA repair circuitry, in conjunction with the rapid development of innovative genome editing technologies, promise to greatly enhance our ability to improve food production, combat environmental pollution, develop cell-based therapies, and cure genetic and infectious diseases.

A detection method for the capture of genomic signatures: From disease diagnosis to genome editing

Variations in the genetic information originate from errors during DNA replication, error-prone repair of DNA damages, or genome editing. The most common approach to detect changes in DNA sequences employs sequencing technologies. However, they remain expensive and time-consuming, limiting their utility for routine laboratory experiments. We recently developed DinucleoTidE Signature CapTure (DTECT). DTECT is a marker-free and versatile detection method that captures targeted dinucleotide signatures resulting from the digestion of genomic amplicons by the type IIS restriction enzyme AcuI. Here, we describe the DTECT protocol to identify mutations introduced by CRISPR-based precision genome editing technologies or resulting from genetic variation. DTECT enables accurate detection of mutations using basic laboratory equipment and off-the-shelf reagents with qualitative or quantitative capture of signatures.

Precise genome engineering in Drosophila using prime editing

Precise genome editing is a valuable tool to study gene function in model organisms. Prime editing, a precise editing system developed in mammalian cells, does not require double-strand breaks or donor DNA and has low off-target effects. Here, we applied prime editing for the model organism Drosophila melanogaster and developed conditions for optimal editing. By expressing prime editing components in cultured cells or somatic cells of transgenic flies, we precisely introduce premature stop codons in three classical visible marker genes, ebony, white, and forked Furthermore, by restricting editing to germ cells, we demonstrate efficient germ-line transmission of a precise edit in ebony to 36% of progeny. Our results suggest that prime editing is a useful system in Drosophila to study gene function, such as engineering precise point mutations, deletions, or epitope tags.

CRISPR-based strategies for targeted transgene knock-in and gene correction

The last few years have seen tremendous advances in CRISPR-mediated genome editing. Great efforts have been made to improve the efficiency, specificity, editing window, and targeting scope of CRISPR/Cas9-mediated transgene knock-in and gene correction. In this article, we comprehensively review recent progress in CRISPR-based strategies for targeted transgene knock-in and gene correction in both homology-dependent and homology-independent approaches. We cover homology-directed repair (HDR), synthesis-dependent strand annealing (SDSA), microhomology-mediated end joining (MMEJ), and homology-mediated end joining (HMEJ) pathways for a homology-dependent strategy and alternative DNA repair pathways such as non-homologous end joining (NHEJ), base excision repair (BER), and mismatch repair (MMR) for a homology-independent strategy. We also discuss base editing and prime editing that enable direct conversion of nucleotides in genomic DNA without damaging the DNA or requiring donor DNA. Notably, we illustrate the key mechanisms and design principles for each strategy, providing design guidelines for multiplex, flexible, scarless gene insertion and replacement at high efficiency and specificity. In addition, we highlight next-generation base editors that provide higher editing efficiency, fewer undesired by-products, and broader targeting scope.