Fluorescent Nucleoside Phosphates for Live Cell RNA Imaging
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Solution Overview
Problem
Current fluorescence-based technologies for studying RNA localization and mechanisms are limited by the use of highly amphiphilic and bulky external constructs that can impair RNA motility and molecular interactions, and are often incompatible with live cell imaging, leading to incomplete understanding of RNA endosomal escape and cellular processing.
Innovation Solution
Development of non-cytotoxic fluorescent nucleoside phosphates that spontaneously accumulate in cells, allowing for endogenous labeling of RNA, minimizing perturbation and enabling live cell imaging and mechanistic studies through incorporation into endogenous RNA molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly amphiphilic and bulky external fluorescent constructs are used to study RNA localization, then fluorescence detection is achieved, but RNA motility is impaired and molecular interactions are perturbed
Solution Approach 1:
The fluorescent label is segmented from the RNA molecule itself, incorporated only at the 5' end during transcription, rather than attached as a bulky external construct. This segmentation maintains the natural properties of the RNA while providing fluorescence detection capability.
Solution Approach 2:
The fluorescent nucleoside is nested within the RNA structure during transcription, with the fluorophore incorporated as part of the nucleoside unit itself. This nested incorporation allows the fluorophore to be an integral part of the RNA molecule without disrupting its overall structure and function.
2Measurement precision
If heavily modified oligonucleotides are used for RNA analysis, then RNA can be analysed and quantified, but ability to be recognized and processed by enzymatic machinery is lost
Solution Approach 1:
Modification is localized to a single nucleoside unit (the fluorescent nucleoside at the 5' end) rather than heavy modification throughout the oligonucleotide. This local modification maintains the natural properties of the rest of the RNA molecule, allowing enzymatic machinery to recognize and process it normally.
Solution Approach 2:
The fluorescent nucleoside is designed to be as homogeneous and similar to natural nucleosides as possible, with minimal structural deviations. This homogeneity allows enzymatic machinery to process the modified RNA similarly to unmodified RNA, maintaining compatibility with cellular processes.
3Measurement precision
If external fluorescent constructs are used for RNA labeling, then fluorescence-based imaging is achieved, but compatibility with live cell imaging is reduced
Solution Approach 1:
The fluorescent label is incorporated into the RNA molecule through the cell's own transcription machinery, rather than requiring external transfection or labeling procedures. This self-service approach allows live cell imaging without disrupting cell viability or requiring invasive interventions.
Solution Approach 2:
The fluorescent nucleoside parameters (size, charge, hydrophobicity) are optimized to be as close to natural nucleosides as possible, allowing the labeled RNA to behave similarly to unlabeled RNA in live cells. This parameter optimization ensures compatibility with live cell imaging while maintaining fluorescence detection capability.
4Measurement precision
If fluorescent labels are incorporated into RNA, then RNA can be visualized, but the label may perturb the processes being observed
Solution Approach 1:
The fluorophore is extracted and incorporated only at the 5' end of the RNA molecule, separate from the functional regions of the RNA. This extraction and localized incorporation minimizes the fluorophore's potential to perturb RNA-protein interactions and other functional processes.
Solution Approach 2:
The fluorescent nucleoside is designed as a minimal perturbation label, with the fluorophore being as small and biologically inert as possible. This approach treats the fluorophore as a disposable detection element that minimally interferes with the biological processes being observed.
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
Enables non-invasive, non-genetic fluorescent labeling of RNA, allowing for visualization of RNA production, transport, processing, and protein interactions in living cells, facilitating new approaches to RNA-based therapies and improved understanding of RNA-mediated mechanisms.
Implementation Method 1
The phosphates spontaneously accumulate in cultured human cells following uptake via an energy-dependent pathway
Implementation Method 2
Once in the cell, enzymes accept the synthetic phosphates as canonical substrates, eventually incorporating them into endogenous cellular RNA
Implementation Method 3
Once incorporated, the labelled residue is minimally perturbing, allowing mechanistic study while minimising the effects of the label on the processes being observed
Data Source
AI summary
This specification discloses novel phosphate compounds of formula (I) useful for labelling RNA in-cellulo. The phosphates are spontaneously taken up by cells and may be used as substrates for RNA synthesis once across the cell membrane. This technology therefore offers a general route to understanding the biological behaviour of RNA of interest, including RNA based drugs.