CROFT-Seq CRISPR Off-Target Detection Method
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Solution Overview
Problem
Current methods for detecting double-strand breaks (DSBs) induced by genome editing nucleases like CRISPR-Cas9 are not sensitive enough, are experimentally complex, lengthy, and costly, making it challenging to ensure the safety and specificity of genome editing technologies.
Innovation Solution
The development of a novel cell-free method, CROFT-Seq, which involves dephosphorylation of DNA ends, biotinylated adapter ligation, affinity purification with streptavidin beads, and subsequent DNA library amplification and sequencing, providing a rapid, cost-effective, and user-friendly approach for detecting off-target sites of CRISPR-Cas9 nucleases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If state of the art methods are used for DSB detection, then detection capability is achieved, but sensitivity is insufficient and experimental complexity increases
Solution Approach 1:
The method segments the detection process into distinct modular steps: adapter ligation to DSB ends, streptavidin bead capture of biotinylated adapters, exonuclease treatment to remove unligated adapters, and sequencing. This segmentation allows each step to be optimized independently and simplifies the overall workflow compared to previous methods
Solution Approach 2:
The patent introduces biotinylated adapters as intermediary molecules that bridge the DSB detection and sequencing processes. The biotin-streptavidin interaction serves as a high-affinity intermediary capture mechanism, enabling selective enrichment of DSB fragments before sequencing while removing background noise through exonuclease treatment
2Measurement precision
If state of the art methods are used for DSB detection, then detection capability is achieved, but cost and time requirements increase
Solution Approach 1:
The method performs preliminary dephosphorylation of DNA ends before adapter ligation to prevent non-specific ligation at non-DSB sites. This preliminary action ensures that only true DSB fragments are captured and sequenced, reducing the need for extensive post-processing and validation steps that consume time and resources
Solution Approach 2:
The protocol skips unnecessary intermediate purification steps by using streptavidin bead capture followed directly by exonuclease treatment and library preparation. This streamlined approach rushes through the detection process efficiently while maintaining high sensitivity, reducing overall detection time compared to traditional multi-step methods
3Measurement precision
If state of the art methods are used for DSB detection, then detection capability is achieved, but cost increases
Solution Approach 1:
The patent changes key parameters including using biotinylated adapters with optimized sequences for efficient ligation, adjusting exonuclease treatment conditions to completely remove unligated adapters, and optimizing streptavidin bead-to-DNA ratios. These parameter changes reduce reagent consumption and improve detection efficiency, lowering overall cost while maintaining sensitivity
Solution Approach 2:
The method employs disposable biotinylated adapters that are inexpensive to synthesize and can be used in a single ligation reaction. These short-living adapter molecules are discarded after serving their capture function, eliminating the need for expensive reusable detection reagents or complex instrument setups
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
CROFT-Seq offers sensitive and unbiased detection of DSBs, reducing costs and experimental complexity, enabling more efficient identification of off-target sites with higher sensitivity and lower DNA requirements, making it suitable for low-budget laboratories and clinical applications.
Implementation Method 1
an adapter comprises a biotin for the purification of the ligated DNA
Implementation Method 2
incubating the samples under conditions sufficient to remove of the unligated adapter with exonuclease I
Implementation Method 3
optionally adding polyC tail to the 3′DNA end with terminal deoxynucleotidyl transferase (TdT) under conditions required to generate polyC tail of an average length of about 10-50 nt
Data Source
AI summary
Rapid, sensitive and cost-efficient detection and characterization method for in vitro double strand breaks produced by CRISPR-Cas9 nucleases from human genomic DNA samples.