Gene Editing Timing Strategy for HDR-NHEJ Trade-off
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Solution Overview
Problem
The kinetics of DNA double-strand break (DSB) repair mechanisms, particularly for TALEN-induced breaks, are not well understood, and existing gene editing methods face challenges in achieving efficient targeted and controllable gene knock-in, relying heavily on error-prone non-homologous end joining (NHEJ) rather than homology-directed repair (HDR).
Innovation Solution
A method involving the use of sequence-specific endonucleases like TALEN or Cas9 to create DSBs at genomic loci, followed by the introduction of a DNA template at specific times to facilitate targeted insertion through homologous recombination or other repair pathways, optimizing the timing and conditions for enhanced gene integration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sequence-specific endonucleases are used to create DSBs for gene editing, then targeted gene insertion is enabled, but the repair process becomes error-prone due to dominance of NHEJ over HDR
Solution Approach 1:
The patent applies preliminary action by introducing the DNA template before the endonuclease is fully active or at optimized time points prior to peak NHEJ activity. This timing strategy allows HDR to occur before error-prone NHEJ dominates, thereby improving repair accuracy while maintaining targeted insertion capability
Solution Approach 2:
The patent employs parameter changes by optimizing multiple variables including DNA template concentration, endonuclease dosage, cell cycle stage, and incubation time. These parameter adjustments shift the balance between HDR and NHEJ pathways, enhancing repair accuracy without sacrificing targeted insertion efficiency
2Productivity
If DNA template is introduced immediately after endonuclease treatment, then repair substrate is available, but gene integration efficiency remains low due to rapid NHEJ activity
Solution Approach 1:
The patent uses preliminary action by pre-preparing and pre-warming DNA templates, and by optimizing the timing of template introduction to coincide with optimal HDR windows. This ensures the repair substrate is ready when conditions favor accurate repair rather than rapid but error-prone NHEJ
Solution Approach 2:
The patent applies periodic action through optimized pulsed endonuclease treatment followed by controlled DNA template introduction at specific time intervals. This periodic approach creates temporal windows where HDR can outcompete NHEJ, thereby improving both integration efficiency and targeted insertion accuracy
3Reliability
If longer incubation time is allowed for HDR, then repair accuracy improves, but productivity decreases due to extended culture time
Solution Approach 1:
The patent employs parameter changes by optimizing incubation time in combination with other variables such as temperature, DNA template concentration, and endonuclease dosage. This multi-parameter optimization achieves high HDR efficiency within shorter timeframes, maintaining both reliability and productivity
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
This approach provides insights into the kinetics of NHEJ and HDR, improving the efficiency and accuracy of gene editing by allowing controlled insertion of exogenous sequences at specific genomic loci, enhancing the precision of gene knock-in processes.
Implementation Method 1
followed by the introduction of a DNA template at specific times to facilitate targeted insertion through homologous recombination
Implementation Method 2
relying heavily on error-prone non-homologous end joining (NHEJ) rather than homology-directed repair (HDR)
Data Source
AI summary
The present disclosure provides methods for targeted insertion of an exogenous sequence at a genomic locus in a cell, wherein said insertion is induced by a sequence-specific endonuclease that has cleavage activity at said locus, at least 5 hours before the introduction into said cell of a DNA template comprising said exogenous sequence.