Methylation Assay Using Flap Detection for Methylated DNA
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Solution Overview
Problem
Current methods are inadequate for efficiently detecting methylated DNA, particularly in the context of gene regulation and cancer diagnosis, due to challenges in distinguishing between unmethylated and methylated cytosines in DNA samples.
Innovation Solution
A method involving treating nucleic acid samples with an agent to convert unmethylated cytosines to uracil, followed by amplification using methylation-specific primers and a flap assay to detect methylated genomic loci using invasive oligonucleotides and flap endonucleases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DNA detection methods are used, then detection can be performed, but the ability to distinguish between unmethylated and methylated cytosines is insufficient
Solution Approach 1:
The patent applies preliminary action by treating the DNA sample with an agent (such as bisulfite) that converts unmethylated cytosines to uracil before detection. This pre-treatment step creates a permanent chemical distinction between methylated and unmethylated cytosines, enabling subsequent specific detection of methylated DNA sequences that retain cytosine residues.
Solution Approach 2:
The patent changes the chemical parameter of cytosine residues through chemical modification. Unmethylated cytosines are converted to uracil, fundamentally altering their chemical identity and allowing differentiation from methylated cytosines that resist this conversion. This parameter change enables specific primer binding and detection strategies.
2Reliability
If methylation-specific primers are used for amplification, then methylated copies can be preferentially amplified, but the complexity of the detection method increases
Solution Approach 1:
The patent introduces an intermediary flap oligonucleotide that serves as a mediator between the amplified DNA and the detection system. This flap oligo contains a 3' terminal nucleotide that specifically base-pairs with methylated cytosine, acting as a bridge that enables specific detection of methylated amplification products through flap endonuclease cleavage.
Solution Approach 2:
The patent replaces direct mechanical/chemical detection of methylation with a biological recognition system. Instead of attempting to directly detect the methyl group, the system uses the natural base-pairing properties of DNA and the specificity of flap endonuclease enzymes to indirectly detect methylation status through sequence-specific recognition and cleavage.
3Measurement precision
If a flap assay with invasive oligonucleotides is employed, then sensitive detection of methylated DNA is achieved, but the overall procedure becomes more complex
Solution Approach 1:
The patent merges multiple functions into a single integrated assay procedure. The flap assay is combined with PCR amplification and chemical treatment steps into a unified workflow where each step builds upon the previous one, allowing simultaneous achievement of DNA amplification, methylation-specific enrichment, and sensitive detection in a coordinated manner.
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 accurate and sensitive detection of methylated DNA, facilitating early cancer detection and monitoring by preferentially amplifying and identifying methylated copies within the sample.
Implementation Method 1
treating a nucleic acid sample that contains both unmethylated and methylated copies of a genomic locus with an agent that modifies cytosine to uracil
Implementation Method 2
employing a flap assay that employs an invasive oligonucleotide having a 3′ terminal G or C nucleotide that corresponds to a site of methylation in the genomic locus
Data Source
AI summary
A method for detecting a methylated genomic locus is provided. In certain embodiments, the method comprises: a) treating a nucleic acid sample that contains both unmethylated and methylated copies of a genomic locus with an agent that modifies cytosine to uracil to produce a treated nucleic acid; b) amplifying a product from the treated nucleic acid using a first primer and a second primer, wherein the first primer hybridizes to a site in the locus that contain methylcytosines and the amplifying preferentially amplifies the methylated copies of the genomic locus, to produce an amplified sample; and c) detecting the presence of amplified methylated copies of the genomic locus in the amplified sample using a flap assay that employs an invasive oligonucleotide having a 3′ terminal G or C nucleotide that corresponds to a site of methylation in the genomic locus.