Single-Cell DNA Methylation Profiling via Multiple Displacement Amplification
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Solution Overview
Problem
Current methods for analyzing chromatin architecture and DNA methylation status are inadequate for single cells or limited quantities, as they require large DNA amounts and are prone to DNA loss and random strand breakage, failing to accurately represent individual cell states due to averaging across heterogeneous cell populations.
Innovation Solution
The development of methods utilizing multiple displacement amplification (MDA) and PCR-based techniques to selectively enrich larger DNA fragments, allowing for the identification of closed chromatin regions, DNase I Hyper-Resistant Sites, and differentially methylated regions, while minimizing DNA loss and random damage, enabling analysis at single nucleotide resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional DNA analysis methods are used on large cell populations, then sufficient DNA quantity is available for analysis, but the results represent averaged data that fail to capture individual cell states
Solution Approach 1:
The patent segments the heterogeneous cell population into individual single cells for separate analysis. By isolating and analyzing each cell individually rather than as a bulk population, the method preserves individual cell state information while overcoming the quantity limitation through subsequent amplification of each cell's DNA separately
Solution Approach 2:
The patent uses multiple displacement amplification (MDA) to create copies of the limited DNA from single cells. This copying process generates sufficient DNA quantity from the original single-cell amount while maintaining the ability to trace back to the individual cell of origin, thus resolving the contradiction between DNA quantity availability and single-cell resolution
2Quantity of substance
If multiple displacement amplification is used to amplify DNA from single cells, then sufficient DNA quantity is generated for analysis, but random strand breakage and DNA loss may occur
Solution Approach 1:
The patent performs preliminary actions to protect DNA integrity before amplification: cells are fixed and permeabilized in a controlled manner, and the amplification process uses optimized conditions (phi29 polymerase with specific buffers) to minimize random strand breakage during the amplification process itself
Solution Approach 2:
The patent optimizes amplification parameters including using phi29 polymerase with high processivity and strand displacement capability, controlling reaction temperature and time, and adjusting buffer composition to reduce DNA damage while maintaining amplification efficiency. These parameter changes balance DNA quantity generation with DNA integrity preservation
3Difficulty of detecting and measuring
If DNase I digestion is used to identify open chromatin regions, then accessible chromatin sites are detected, but closed chromatin regions may be damaged or lost
Solution Approach 1:
The patent extracts and analyzes open chromatin regions (DNase I hypersensitive sites) separately from closed chromatin regions. By taking out the accessible DNA fragments through selective digestion and size selection, the method detects open chromatin sites while leaving the majority of closed chromatin DNA intact for separate analysis
Solution Approach 2:
Instead of directly analyzing closed chromatin, the patent inverts the approach by digesting and removing open chromatin regions, then analyzing what remains. This indirect method allows identification of closed chromatin sites as the protected, undigested fragments, thereby detecting closed chromatin without directly exposing it to damaging conditions
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
These methods enable sensitive profiling of chromatin architecture and methylation status in single cells or small populations, reducing DNA loss and random damage, and providing accurate representation of individual cell states, suitable for clinical and diagnostic applications.
Implementation Method 1
amplification of the DNA by multiple displacement amplification to produce amplicons
Implementation Method 2
digesting genomic DNA with DNase I or other endonucleases
Implementation Method 3
PCR-based techniques to selectively enrich larger DNA fragments
Data Source
AI summary
Methods of identifying DNase I Hyper-Resistant Sites (DHRS), or in board sense, highly compact chromatin and characterizing the DNA methylation status of DMRs such as CpG islands and CpG island shores are provided. The methods are particularly useful for analysis of genomic DNA from low quantities of cells, for example, less than 1,000 cells, less than 100 cells, less than 10 cells, or even one cell, and can be used to generate chromatin and methylation profiles. The downstream analyses include in parallel massive sequencing, microarray, PCR and Sanger sequencing, hybridization and other platforms. These methods can be used to generate chromatin and DNA methylation profiles in drug development, diagnostics, and therapeutic applications are also provided.