Bisulfite-Treated DNA Amplification for Single-Cell Methylation Mapping
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Solution Overview
Problem
Current methods for detecting 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) in small amounts of DNA or single cells are limited in resolution and require large quantities of DNA, making them unsuitable for rare samples or single cell systems.
Innovation Solution
A method involving ligation of an adaptor with a bisulfite-protected RNA polymerase promoter, followed by bisulfite treatment, primer hybridization, and in vitro transcription to amplify bisulfite-treated DNA, enabling detection of 5mC and 5hmC in limited DNA samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current bisulfite conversion-based methods are used to detect 5mC and 5hmC, then quantitative differentiation at single-base resolution is achieved, but large quantities of DNA (micrograms) are required
Solution Approach 1:
The method segments the DNA analysis process into distinct phases: bisulfite conversion of input DNA, adapter ligation, and in vitro transcription amplification. This segmentation allows the initial bisulfite conversion to work with minimal DNA while subsequent amplification generates sufficient material for high-resolution analysis, resolving the contradiction between precision and quantity requirements
Solution Approach 2:
The adaptor is designed with pre-installed RNA polymerase promoter sequences containing protected cytosines before the bisulfite treatment step. This preliminary action ensures that the amplification framework is already in place before amplification begins, enabling the method to work with trace amounts of input DNA while maintaining single-base resolution capability
2Quantity of substance
If affinity capture-based methods are used, then low input DNA requirements are met, but resolution is reduced and information is lost
Solution Approach 1:
The method introduces an adaptor as an intermediary molecule that bridges the bisulfite-converted DNA and the amplification/sequencing processes. This adaptor contains protected cytosines that serve as fiducial markers, enabling high-resolution mapping while allowing the method to work with low input DNA quantities, thus resolving the contradiction between quantity and precision
3Quantity of substance
If restriction endonuclease methods are used, then low DNA input is acceptable, but resolution is limited by sequence specificity
Solution Approach 1:
The method changes the fundamental parameter of how cytosines are distinguished - instead of relying on restriction enzyme sequence specificity, it uses bisulfite conversion chemistry that differentiates cytosines based on their methylation state. Combined with protected cytosines in the adaptor, this enables high-resolution coverage without being limited by sequence specificity, resolving the contradiction between low input requirements and resolution
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 high-resolution detection of 5mC and 5hmC in small DNA amounts, providing unbiased genome analysis suitable for single cell studies and rare samples without loss of methylation information.
Implementation Method 1
hybridizing the bisulfite-treated DNA molecules with a primer
Implementation Method 2
in vitro transcribing the double-stranded DNA to make RNA
Implementation Method 3
treating the ligated DNA molecules with bisulfite
Data Source
AI summary
The methods, compositions, and kits of the disclosure provide a novel approach for a whole genome, unbiased DNA analysis method that can be performed on limited amounts of DNA can be used to analyze DNA to determine its modification status. Aspects of the disclosure relate to a method for amplifying bisulfite-treated deoxyribonucleic acid (DNA) molecules comprising: (a) ligating an adaptor to the DNA molecules, wherein the adaptor comprises a RNA polymerase promoter comprising bisulfite-protected cytosines; (b) treating the ligated DNA molecules with bisulfite; (c) hybridizing the bisulfite-treated DNA molecules with a primer; (d) extending the hybridized primer to make double stranded DNA; and (e) in vitro transcribing the double-stranded DNA to make RNA.