Single Cell Gene Expression Analysis via Droplet Barcoding
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Solution Overview
Problem
Current methods for gene expression profiling, such as microarray hybridization and bulk mRNA sequencing, are limited in analyzing alternative splicing, promoters, and polyadenylation signals, and fail to capture the functional information from single cells, leading to loss of distinct cell types and dynamic processes.
Innovation Solution
A method for preparing cDNA libraries from single cells using droplets and beads with unique barcodes, involving mRNA release, first strand synthesis, tag incorporation, pooling, amplification, and tagmentation to generate tagged cDNA fragments, enabling multiplexed single cell gene expression analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bulk mRNA sequencing is used to analyze gene expression, then the analysis can be performed on large tissue samples, but the functional information from single cells is lost or blurred
Solution Approach 1:
The patent segments the tissue sample into individual single cells, with each cell being processed separately in droplets. This segmentation allows the mRNA from each cell to be individually reverse transcribed and barcoded, preserving single-cell functional information while still enabling analysis of large numbers of cells in parallel
Solution Approach 2:
The patent creates digital copies of single-cell mRNA through cDNA synthesis with unique barcodes. Each cell's mRNA is converted to barcoded cDNA copies that can be pooled and sequenced together, allowing reconstruction of single-cell expression profiles from bulk sequencing data
2Measurement precision
If microarray hybridization is used for gene expression profiling, then previously known genes can be analyzed, but alternative splicing, promoters and polyadenylation signals cannot be analyzed
Solution Approach 1:
The patent changes the fundamental parameter of gene expression analysis from hybridization-based detection to sequencing-based detection. This allows analysis of any RNA sequence including alternative splicing variants, promoters, and polyadenylation signals, not just pre-defined genes on the microarray
Solution Approach 2:
The sequencing-based approach provides universal applicability for analyzing all types of RNA elements - coding genes, alternative splicing variants, promoters, and polyadenylation signals - making the method multi-functional compared to the gene-specific microarray approach
3Measurement precision
If single cells are isolated for study using cell-surface markers, then distinct cell types can be identified, but a small number of single cells are not sufficient to capture the range of natural variation in gene expression
Solution Approach 1:
The patent segments the analysis into two levels: first isolating individual single cells (providing cell type identification), then pooling many such single-cell cDNA samples (providing statistical power). The unique barcodes maintain the connection between pooled sequences and their original single-cell sources
Solution Approach 2:
The patent merges multiple single-cell cDNA samples into a pooled library for simultaneous sequencing. Each sample retains its unique barcode, allowing computational deconvolution to reconstruct individual cell profiles from the pooled data, thus combining the benefits of single-cell resolution with bulk sequencing depth
4Measurement precision
If droplets and beads with unique barcodes are used for multiplexed single cell analysis, then sensitivity and dynamic range are improved, but the device complexity increases
Solution Approach 1:
The patent uses beads with barcoded primers as intermediaries between the single cells and the sequencing platform. Each bead carries unique barcodes that are incorporated into the cDNA during reverse transcription, serving as a mediator that enables tracking of individual cell origins throughout the complex multiplexed workflow
Solution Approach 2:
The patent performs preliminary barcoding of cDNA during the reverse transcription step itself, rather than adding barcodes later. This preliminary action integrates the identification function into the amplification process, reducing the number of separate steps needed and simplifying the overall workflow despite the complexity of droplet handling
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 allows for detailed analysis of gene expression in individual cells, preserving functional information and enabling the study of distinct cell types and dynamic processes, improving sensitivity and dynamic range compared to existing methods.
Implementation Method 1
performing a tagmentation reaction to simultaneously cleave each cDNA and incorporate an adapter into each strand of the cDNA, thereby generating a plurality of tagged cDNA fragments, wherein the tagmentation reaction comprises contacting the double-stranded cDNA with a transposase mixture comprising an adapter sequence
Implementation Method 2
synthesizing a first strand of cDNA from the mRNA in each individual mRNA sample with a first strand synthesis primer
Data Source
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AI summary
Presented herein are methods and compositions for multiplexed single cell gene expression analysis. Some methods and compositions include the use of droplets and/or beads bearing unique barcodes such as unique molecular barcodes (UMI).