CRISPR Off-Target Sequencing With Biotin Capture and Low Background
Find Innovative SolutionsGenerate Solutions
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, lacking user-friendliness, especially for low-budget laboratories and companies.
Innovation Solution
The CROFT-seq method involves dephosphorylation of DNA ends, ligation of biotinylated adapters, affinity purification using streptavidin beads, and synthesis of complementary strands for PCR library amplification and sequencing, eliminating the need for magnetic bead-based adapter removal and reducing background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods for DSB detection are used, then detection capability is achieved, but sensitivity is insufficient and experimental complexity is high
Solution Approach 1:
The method segments the detection process into distinct functional modules: adapter ligation module, purification module using streptavidin beads, exonuclease treatment module, and sequencing module. This segmentation allows each module to be optimized independently, improving overall sensitivity while reducing operational complexity through standardized protocols.
Solution Approach 2:
Biotinylated adapters serve as intermediary molecules that bridge the DSB detection function and the streptavidin bead purification system. This intermediary approach enables highly sensitive detection by allowing specific capture of ligated DNA fragments while eliminating unligated adapters through exonuclease treatment, thereby improving signal-to-noise ratio without increasing experimental complexity.
2Measurement precision
If current methods for DSB detection are used, then detection capability is achieved, but cost is high and user-friendliness is poor
Solution Approach 1:
The method employs exonuclease I to automatically remove unligated adapters from the reaction mixture. This self-service mechanism eliminates the need for manual intervention in adapter removal steps, reducing both cost and operational complexity while maintaining high detection sensitivity. The enzyme naturally distinguishes between ligated and unligated adapters based on their structural properties.
Solution Approach 2:
The method optimizes reaction parameters such as exonuclease concentration, incubation temperature, and time to achieve complete removal of unligated adapters while preserving ligated fragments. These parameter optimizations make the protocol more user-friendly by reducing the need for complex optimization steps while maintaining high detection sensitivity.
3Measurement precision
If current methods for DSB detection are used, then detection capability is achieved, but background noise is high
Solution Approach 1:
The method converts the potential harm of unligated adapters (which contribute to background noise) into a benefit by using their single-stranded nature as a recognition feature. Exonuclease I specifically targets and degrades these single-stranded unligated adapters while leaving double-stranded ligated fragments intact. This transforms the noise-generating molecules into easily removable byproducts, dramatically improving the signal-to-noise ratio.
4Measurement precision
If current methods for DSB detection are used, then detection capability is achieved, but processing time is lengthy
Solution Approach 1:
The method performs preliminary dephosphorylation of DNA ends before adapter ligation to prevent re-ligation of DNA fragments. This preliminary action simplifies subsequent steps by ensuring that only properly ligated fragments remain, reducing the need for additional purification steps and thereby decreasing overall processing time while maintaining high detection sensitivity.
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 provides sensitive, rapid, and cost-effective detection of DSBs, producing approximately 10 times more reads than other methods, suitable for automation, and effective with low DNA yields, making it suitable for various cells and tissues.
Implementation Method 1
incubating the samples under conditions sufficient to remove of the unligated adapter with exonuclease I
Implementation Method 2
capturing ligated DNA on to streptavidin magnetic beads
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
Implementation Method 4
optionally fragmenting DNA with DNase I under conditions required to fragment DNA to an average length of about 100-500 bp
Data Source
Figure 1
Figure 2
Figure 3
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.