In Situ Combinatorial Barcoding for Single-Cell RNA Sequencing
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Solution Overview
Problem
Current Next Generation Sequencing (NGS) methods struggle to identify and quantify individual transcripts from cells in large samples, as they mix RNA transcripts from multiple cells, making it difficult to link expression back to individual cells, and alternative techniques like microscopy or manual separation are cumbersome or limited in scalability.
Innovation Solution
A method involving fixing and permeabilizing cells, followed by reverse transcription to form cDNA, then dividing and tagging cells with unique nucleic acid tags in multiple rounds to create a unique barcode for each cell, allowing for the sequencing of individual transcripts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If RNA transcripts are purified from lysed cells and converted to cDNA using NGS, then RNA expression can be measured for the whole sample, but individual sequences cannot be linked back to an individual cell
Solution Approach 1:
The method segments the processing by dividing cells into individual reaction vessels where each cell's transcripts are converted to cDNA and tagged with unique barcodes. This segmentation allows tracking of individual cell transcripts while maintaining the ability to process many cells in parallel through subsequent pooling and mixing steps.
Solution Approach 2:
Unique nucleic acid tags or barcodes serve as intermediaries that link individual cell transcripts to their cell of origin. These barcodes are incorporated during reverse transcription and persist through sequencing, enabling computational reconstruction of which transcripts came from which cell without requiring physical separation during analysis.
2Measurement precision
If manual separation of individual cells into separate reaction vessels is used, then individual cell transcripts can be uniquely labeled, but the process becomes too complicated for large samples
Solution Approach 1:
The method merges multiple operations into unified steps: reverse transcription and barcode incorporation occur simultaneously in a single reaction, and cells are pooled together after individual labeling rather than remaining separated. This merging dramatically reduces the number of separate operations needed while maintaining single-cell resolution.
Solution Approach 2:
The reverse transcription primer serves multiple functions: it initiates cDNA synthesis from RNA templates and simultaneously incorporates the unique cell barcode into each cDNA molecule. This multi-functionality eliminates the need for separate labeling steps, simplifying the overall process.
3Measurement precision
If microscopy is used to identify individual fluorescent bases, then individual cell sequencing is possible, but the technique is limited to a low number of cells
Solution Approach 1:
Instead of directly imaging individual transcripts in each cell, the method creates copies of cell identity information (barcodes) that are attached to cDNA molecules. These barcode copies can be amplified and detected through sequencing, allowing many more cells to be analyzed than would be feasible with direct microscopy of fluorescent bases.
Solution Approach 2:
The method replaces the mechanical/optical system of microscopy and fluorescent base identification with a biochemical system using nucleic acid barcodes and sequencing. This substitution enables scaling from analyzing a few cells via microscopy to analyzing thousands or millions of cells via high-throughput sequencing.
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 the sequencing of RNA expression at the single-cell level by ensuring each cell has a unique barcode, facilitating the identification and analysis of transcriptomes from multiple cells.
Implementation Method 1
reverse transcribing the RNA molecules within the first plurality of cells to form complementary DNA (cDNA) molecules within the first plurality of cells
Data Source
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AI summary
Methods of uniquely labeling or barcoding molecules within a nucleus, a plurality of nuclei, a cell, a plurality of cells, and/or a tissue are provided. Kits for uniquely labeling or barcoding molecules within a nucleus, a plurality of nuclei, a cell, a plurality of cells, and/or a tissue are also provided. The molecules to be labeled may include, but are not limited to, RNAs and/or cDNAs.