Modified gRNA for Targeted Gene Activation
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Solution Overview
Problem
Current CRISPR/Cas9-mediated epigenetic editing systems, such as the dCas9-VP64 system, face inefficiencies in targeting gene activation in vivo due to insufficient transduction of Cas9 fusion proteins and low levels of transcriptional activation, limiting their utility for therapeutic applications and experimental purposes.
Innovation Solution
Development of modified guide RNAs (gRNAs), including 'dead' gRNAs (dgRNAs) with increased GC content and shortened repetitive sequences, which are used in conjunction with a dCas9 protein and an MS2-transcriptional activator fusion protein to enhance targeted gene activation without inducing DNA double-strand breaks, utilizing viral vectors like AAV for delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the original dCas9-VP64 system is used for targeted gene activation, then the system can be implemented with existing tools, but the transcriptional activation efficiency is low and insufficient robust target gene activation is achieved
Solution Approach 1:
The patent combines multiple transcriptional activation domains (VP64, VPR, and SAM) into a single integrated system. The modified gRNA incorporates multiple MS2 binding loops that recruit multiple activator proteins simultaneously, creating a synergistic effect that dramatically enhances transcriptional activation efficiency while ensuring robust target gene activation.
Solution Approach 2:
The invention creates a composite molecular system by integrating multiple functional elements: the dCas9 protein fused with multiple activation domains (VP64-VPR-SAM), combined with a modified gRNA containing multiple MS2 binding loops. This composite structure allows simultaneous recruitment of multiple transcriptional activators to the target gene, achieving both high efficiency and robustness.
2Productivity
If multiple sgRNAs are recruited to improve TGA efficiency, then transcriptional activation is enhanced, but the system complexity increases and utility is diminished
Solution Approach 1:
The patent merges the functions of multiple sgRNAs into a single modified gRNA molecule. The modified gRNA contains multiple MS2 binding loops integrated into one structure, allowing it to recruit multiple activation domains simultaneously. This consolidation maintains high TGA efficiency while simplifying the system by eliminating the need for multiple separate sgRNA components.
Solution Approach 2:
The modified gRNA serves multiple functions within a single molecule: it provides target recognition through its spacer sequence, recruits multiple transcriptional activators through integrated MS2 binding loops, and maintains structural stability. This multi-functional design eliminates the need for separate components, reducing system complexity while maintaining efficiency.
3Productivity
If second-generation CRISPR/Cas9 TGA systems (dCas9-VPR, SAM, dCas9-Suntag) are used, then in vitro TGA efficiency is improved, but in vivo transduction is insufficient and low levels of TGA are achieved
Solution Approach 1:
The patent optimizes key parameters of the TGA system for in vivo performance. The modified gRNA incorporates multiple MS2 binding loops with optimized spacing and orientation, and the dCas9 fusion protein combines multiple activation domains in a specific configuration. These parameter optimizations enable efficient transduction and robust TGA in vivo, overcoming the limitations of previous second-generation systems.
Solution Approach 2:
The invention creates an optimized composite system specifically tailored for in vivo application. The dCas9 protein is fused with a specific combination of activation domains (VP64-VPR-SAM), and the modified gRNA contains multiple MS2 binding loops arranged to maximize recruitment efficiency. This composite structure achieves both high in vitro efficiency and robust in vivo transduction.
4Productivity
If sequences encoding dCas9/gRNA and co-transcriptional activator complexes are used, then TGA function is achieved, but the sequences exceed the capacity of common viral vectors for in vivo delivery
Solution Approach 1:
The patent extracts and separates the essential functional elements from the full-length sequences. The modified gRNA contains only the necessary MS2 binding loops and spacer sequence required for TGA function, eliminating redundant regions. The dCas9 fusion protein includes only the essential activation domains needed for robust TGA. This extraction reduces sequence length to fit within viral vector capacity while maintaining full TGA functionality.
Solution Approach 2:
The invention optimizes the sequence parameters by reducing the length of gRNA and protein coding sequences while maintaining functional integrity. The modified gRNA uses compact MS2 binding loop structures, and the dCas9 fusion protein employs efficient domain arrangements. These parameter changes enable delivery within viral vector size constraints while preserving robust TGA function.
Data Source
AI summary
Provided are modified guide RNAs (gRNAs), including dead guide RNAs (dgRNAs) with increased GC content and/or decreased repetitive content, as well as compositions and kits including such dgRNAs, which can be used in a targeted gene activation system, for example to increase expression of a gene to treat a disease in vivo. Such methods increase targeted gene expression, without creating DNA double strand breaks (DSBs).