Methylation Assay Reference DNA for Blood Background Normalization
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Solution Overview
Problem
Existing methylation assays face challenges in accurately quantifying methylation status due to sample-to-sample variations and the need for reliable normalization controls, particularly in the presence of blood cells that can interfere with tissue-derived DNA analysis.
Innovation Solution
The use of reference DNAs, such as ZDHHC1, with methylation patterns similar to tissue-specific markers, allows for normalization and quantification by exposing them to the same preparative steps as marker DNAs, enabling accurate comparison and detection of tissue cells even in samples containing blood cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional normalization controls (e.g., β-actin) are used in methylation assays, then sample-to-sample variations can be normalized, but blood cells in the sample produce background signal that interferes with accurate detection of tissue-derived DNA
Solution Approach 1:
The patent introduces an intermediary control nucleic acid sequence that specifically targets tissue-derived DNA while being absent or low-abundance in blood cells. This intermediary acts as a mediator between the sample and the detection system, enabling selective normalization to tissue DNA and filtering out blood cell background interference through differential methylation patterns.
Solution Approach 2:
The patent applies local quality by selecting control sequences with specific tissue-type methylation patterns that differ from blood cells. Rather than using a universal control, the control sequence is tailored to have high methylation in tissue cells and low methylation in blood cells, creating localized specificity for tissue-derived DNA in mixed samples.
2Measurement precision
If reference DNAs with similar methylation features to tissue-specific markers are used, then accurate normalization and quantification can be achieved, but the complexity of selecting and validating appropriate reference DNAs increases
Solution Approach 1:
The patent uses copying by selecting control nucleic acid sequences that are genomic copies or homologs of the target tissue-specific marker sequences. These control sequences share similar methylation patterns and structural features with the target markers, allowing them to serve as faithful replicas for normalization purposes without requiring de novo validation of each control sequence.
Solution Approach 2:
The patent applies universality by identifying control sequences that can serve multiple functions: they act as normalization controls for tissue-derived DNA, provide internal references for methylation status determination, and function across different sample types and processing conditions. This multi-functionality reduces the need for separate validation procedures for each application.
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 provides reliable normalization and enhances the accuracy of methylation assays by accounting for sample variations, allowing for the detection of tissue cells and metastasis in blood samples, particularly useful in cancer diagnostics.
Implementation Method 1
processing typically comprises treatment with bisulfite to convert un-methylated dC bases to dU residues, making them more readily distinguishable from the methyl-C residues that are protected from bisulfite conversion
Data Source
AI summary
Provided herein is technology relating to performing methylation assays. In particular, the technology relates to internal controls for methylation assays.