TALE Base Editor Scaffolds for Precise Gene Editing Specificity
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Solution Overview
Problem
Existing TALE-base editors face challenges in efficiently targeting specific genomic sequences in human cells for gene editing while minimizing off-target mutations, particularly in immune therapeutic cells, due to the complexity and variability of human genomes.
Innovation Solution
The development of TALEB scaffolds with refined target sequences and fusion proteins, including split DddA-derived cytosine base editors and uracil glycosylase inhibitors, to precisely convert cytosine to thymine within defined genomic windows, minimizing off-target effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TALE-base editors are used for gene editing in human cells, then editing activity can be achieved, but off-target mutations increase and specificity decreases
Solution Approach 1:
The patent applies local quality by designing TALE-repeat units with specific RVD compositions tailored to local sequence contexts. Different RVDs (HD, NG, NI, NK, NH, NN) are strategically assigned to different positions within the target sequence based on the underlying DNA sequence and local chromatin features, optimizing binding affinity and specificity for each local region while minimizing off-target effects.
Solution Approach 2:
The patent implements parameter changes by systematically varying multiple parameters of the TALE-base editor system: RVD composition and arrangement, repeat number (typically 18-25 repeats), spacer length and sequence, deaminase domain selection (AID, APOBEC1, DddA), and fusion protein architecture. These parameter optimizations collectively enhance on-target activity while reducing off-target mutations.
2Productivity
If TALE-base editors are designed for high activity, then editing efficiency improves, but target sequence specificity decreases
Solution Approach 1:
The patent applies dynamics by creating a flexible design framework where TALE-repeat arrays can be dynamically adjusted to match different target sequences. The modular RVD-based system allows rapid reconfiguration of TALE specificity parameters (repeat number, RVD composition, spacer design) to optimize for both high activity and high specificity depending on the target sequence characteristics and desired editing outcome.
Solution Approach 2:
The patent uses composite materials by fusing TALE DNA-binding domains with deaminase catalytic domains to create hybrid TALE-base editor proteins. This composite architecture combines the sequence-specific targeting capability of TALEs with the catalytic activity of deaminases, enabling precise C-to-T or A-to-G conversions at selected genomic loci with high efficiency and specificity.
3Manufacturing precision
If existing base editor fusion proteins are used, then cytosine to thymine conversion can be achieved, but editing window control is limited
Solution Approach 1:
The patent applies segmentation by dividing the TALE protein into modular repeat units, each containing specific RVDs that recognize individual DNA bases. This segmentation allows precise control over the editing window by adjusting the number, sequence, and arrangement of repeats, enabling targeted editing at specific positions within the binding site while leaving surrounding sequences unaffected.
Solution Approach 2:
The patent uses spacer sequences as intermediaries between the TALE repeat array and the deaminase domain. These spacers (typically 5-20 amino acids) provide flexible linkers that position the deaminase catalytic domain at the appropriate distance and orientation relative to the DNA binding site, enabling precise control over the editing window and facilitating efficient C-to-T conversion at the intended target position.
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 achieves high specificity and efficiency in editing genes like CD52, TCR, and B2M, enhancing the therapeutic potential of immune cells for allogeneic therapies and in vivo gene corrections.
Implementation Method 1
split DddA-derived cytosine base editors and uracil glycosylase inhibitors, to precisely convert cytosine to thymine
Data Source
AI summary
The present invention relates to methods using base editors for efficiently genetically engineer cells, especially primary hematopoietic stem cells (HSCs) and primary immune cells. In particular, the invention is directed to rules for designing highly active and specific TALE-base editors displaying improved on-target/off-target activity ratios useful to manufacture complex gene edited cells of therapeutic grade or to perform in-vivo gene therapy. The resulting TALE-base editors can be used alone or in combination with rare-cutting endonucleases in various gene therapy approaches.