DNA Source Identification via Methylation Ratios
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Solution Overview
Problem
Current methods for identifying the source of DNA samples are inefficient and costly, particularly when dealing with mixed or unknown DNA samples, as they rely on variable methylation levels that can be difficult to quantify accurately.
Innovation Solution
A method involving digestion of DNA with methylation-sensitive and methylation-dependent restriction endonucleases, followed by amplification and calculation of methylation ratios between specific loci, which are then compared to reference ratios to determine the source of the DNA sample, allowing for identification of tissues or cell types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absolute methylation level quantification is used to identify DNA source, then identification accuracy may be improved, but measurement complexity and cost increase
Solution Approach 1:
The patent transforms the measurement approach from absolute methylation levels to relative methylation ratios between different loci. This parameter transformation simplifies the measurement process while maintaining identification capability, as ratios are more stable and easier to quantify than absolute values across different samples and platforms.
Solution Approach 2:
Instead of directly measuring absolute methylation levels in the original DNA sample, the patent uses copy sequences (amplified PCR products) that preserve the relative methylation ratio information. This copying approach enables indirect measurement of the original sample's methylation pattern through simplified ratio comparisons in the amplified copies.
2Reliability
If multiple DNA samples from different tissues are analyzed, then identification reliability improves, but signal mixing and quantification difficulty increase
Solution Approach 1:
The patent segments the DNA analysis into separate loci regions, each with characteristic methylation patterns. By analyzing multiple discrete loci and comparing their relative methylation ratios, the method can distinguish between different tissue sources even when signals are mixed, as each tissue type produces a characteristic ratio pattern across the segmented loci.
Solution Approach 2:
The patent introduces methylation ratios as an intermediary parameter that mediates between the complex mixed signal data and the identification goal. The ratio of methylation levels at different loci serves as a simplified intermediate representation that preserves tissue identity information while filtering out confounding factors like sample mixing and quantitative variability.
3Adaptability or versatility
If methylation analysis is performed to identify tissue source, then source identification capability is improved, but analysis time and cost increase
Solution Approach 1:
Instead of performing comprehensive methylation analysis across the entire genome, the patent applies partial action by focusing on a selected set of informative loci. This partial analysis approach maintains source identification capability while significantly reducing the time and resources required, as only specific loci with diagnostic methylation patterns need to be analyzed.
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 enables rapid, cost-effective, and accurate identification of DNA sample sources by utilizing methylation ratios that are relatively constant across individuals, even in mixed samples, improving upon existing methods by not requiring absolute methylation level quantification.
Implementation Method 1
digesting the DNA sample with a methylation-sensitive and/or methylation-dependent restriction endonuclease
Implementation Method 2
amplifying the digested DNA with at least a first and a second restriction locus, thereby generating an amplification product for each restriction locus
Data Source
AI summary
The present disclosure relates to methodology for fast and cost-effective identification of the source of DNA samples. DNA samples obtained from unknown or unrecognized tissues or cell types are analyzed according to the methodology described herein, yielding an identification of the tissue and/or cell type source. Identification is based on sequential biochemical procedures including methylation sensitive/dependent restriction and polymerase chain reaction, followed by analysis of the data. All biochemical steps are performed in a single test tube. The disclosure has immediate applications in forensic science for identification of the tissue source of DNA obtained from biological stains. The disclosure also has immediate applications in cancer diagnosis for identification.