Dual Recombinase-Mediated Cassette Exchange for Somatic Mosaics
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Solution Overview
Problem
Current non-genetically engineered mouse models (GEMMs) for somatic mosaicism, such as electroporation-mediated and viral gene delivery methods, face limitations like unpredictable genomic integration, immune responses, and clonal genotypic/phenotypic variability, making them unsuitable for precise interrogation of gain-of-function mutations and tumor modeling.
Innovation Solution
The use of dual recombinase-mediated cassette exchange (dRMCE) in heterozygous Rosa26mTmG mice, which allows for precise and controlled gene editing in somatic cells, enabling the generation of somatic mosaics with uniform gene dosage and reduced variability, facilitating the modeling of tumors and cancer driver mutations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electroporation-mediated or viral gene delivery methods are used to create somatic mosaics rapidly, then speed and flexibility are improved, but unpredictable genomic integration, insertional mutagenesis, and clonal genotypic variability occur
Solution Approach 1:
The patent uses a targeted integration system where a donor construct with homology arms acts as an intermediary to guide precise genomic insertion. The donor construct contains the transgene flanked by homology arms that match the target locus, enabling site-specific integration through homologous recombination rather than random insertion. This intermediary mechanism ensures predictable genomic integration while maintaining rapid generation capability.
Solution Approach 2:
The patent replaces the mechanical/random nature of electroporation and viral integration with a biochemical precision system. By using homologous recombination mediated by the donor construct's homology arms, the system substitutes random physical insertion with a controlled biochemical process that targets specific genomic locations, thereby eliminating insertional mutagenesis while preserving speed.
2Loss of time
If non-GEMM techniques like PB-EP or viral delivery are used, then labor and time are reduced, but clonal genotypic/phenotypic variability and transgene copy number variation occur
Solution Approach 1:
The patent extracts the source of variability by removing the transgene from extrachromosomal or randomly integrated forms and placing it into a defined genomic locus. By taking out the transgene and inserting it at a specific location through targeted integration, the system eliminates copy number variation and ensures uniform gene dosage across all cells in the mosaic, while still achieving rapid generation through in vivo electroporation.
Solution Approach 2:
The patent changes the parameter of integration location from random to fixed/specific. By designing the donor construct with homology arms that target a specific genomic locus, the system transforms the integration process from a stochastic event with variable outcomes to a controlled process with consistent results, ensuring uniform transgene copy number and expression levels.
3Manufacturing precision
If GEMM generation is performed to ensure constant gene dosage and zygosity, then gene expression uniformity is improved, but the process becomes laborious and time-consuming
Solution Approach 1:
The patent performs preliminary action by designing the donor construct with built-in homology arms and target site information before the integration event. This pre-prepared donor construct contains all necessary elements (transgene, homology arms, selection markers) required for precise integration, allowing the actual integration process to proceed rapidly in vivo without requiring subsequent cloning or validation steps, thus achieving both precision and efficiency.
Solution Approach 2:
The patent uses a standardized donor construct template that can be repeatedly copied and used for multiple integration events. The donor construct design serves as a reusable template that ensures consistent integration outcomes across different experiments and cell types, eliminating the need for time-consuming GEMM generation while maintaining gene dosage uniformity through identical integration mechanisms.
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
dRMCE provides a robust and efficient method for creating stable, defined somatic mosaics in vivo, overcoming the limitations of existing methods by ensuring uniform gene expression and reducing insertional mutagenesis, thereby enabling precise tumor modeling and drug screening.
Implementation Method 1
dual recombinase-mediated cassette exchange (dRMCE) in heterozygous Rosa26mTmG mice, which allows for precise and controlled gene editing in somatic cells
Implementation Method 2
electroporation-mediated (EP) and viral gene deliveries
Data Source
AI summary
Described herein are donor vectors and systems for use in in vivo dual recombinase-mediated cassette exchange. Also described are animal models for consistent, rigorous, and facile investigation of transgene expression. Further described are methods of screening for therapeutic drugs using these animal models, and methods of treatment.