Modified PNA Probe for Bisulfite-Free DNA Methylation Detection
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Solution Overview
Problem
Existing methods for detecting DNA methylation, such as bisulfite treatment followed by methylation-specific PCR, are limited by the need for large DNA amounts, poor reproducibility, and high error rates, leading to inaccurate and non-specific results.
Innovation Solution
A novel PNA oligomer and probe that can detect DNA methylation without bisulfite treatment, allowing for selective amplification of non-methylated DNA and suppression of methylated DNA, using a PNA probe to differentiate through cycle threshold (Ct) or melting temperature (Tm) differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bisulfite treatment is used to detect DNA methylation, then methylation state can be determined by converting non-methylated cytosines to uracils, but 90% or more of genomic DNA is degraded requiring large amounts of DNA
Solution Approach 1:
The invention extracts and targets only the methylated DNA fraction by using PNA probes that specifically bind to methylated cytosine residues. This selective binding allows detection of methylation without requiring bisulfite treatment that degrades 90% of genomic DNA, thus solving the contradiction between detection accuracy and DNA quantity required.
Solution Approach 2:
The PNA probe acts as an intermediary that specifically recognizes and binds to methylated cytosine residues. This intermediary approach enables direct detection of methylation status without the need for bisulfite conversion, thereby preserving genomic DNA integrity and reducing the large DNA amounts previously required.
2Measurement precision
If bisulfite treatment is used for methylation detection, then non-methylated cytosines are converted to uracils, but errors occur when non-methylated cytosine is not converted or 5-methyl cytosine is maintained, leading to false positive results
Solution Approach 1:
The invention segments the detection approach by using PNA probes that specifically target methylated cytosine residues independently of bisulfite conversion. This segmentation allows direct recognition of methylation status without relying on the error-prone bisulfite conversion process, thereby improving both accuracy and reproducibility.
Solution Approach 2:
The invention converts the previously harmful bisulfite treatment step into a beneficial direct detection approach. By using PNA probes that naturally recognize methylated cytosine residues, the method eliminates the source of errors (incomplete conversion or false maintenance of 5-methyl cytosine) and transforms the detection process into a more reliable system.
3Measurement precision
If methylation-specific PCR is used after bisulfite treatment, then individual cytosine methylation states can be confirmed, but the method is limited in the number of genes and specimens that can be examined at a time
Solution Approach 1:
The PNA probe system provides universal applicability for detecting methylation across multiple genes and specimens simultaneously. The probes can be designed to target different CpG sites and genes using the same fundamental detection principle, enabling high-throughput examination without the limitations of traditional methylation-specific PCR.
Solution Approach 2:
The invention changes the detection parameters by using PNA probes with specific binding characteristics that allow simultaneous examination of multiple targets. The probes can be used in various formats (microarrays, real-time PCR, etc.) enabling parallel processing of multiple genes and specimens, thereby increasing productivity while maintaining precision.
4Measurement precision
If primers are designed for methylation detection after bisulfite conversion, then detection can be performed, but primer design is difficult according to conversion ratio and efficiency, and results show poor reproducibility due to non-specific binding
Solution Approach 1:
The invention inverts the traditional approach by designing PNA probes that directly target methylated cytosine residues without requiring bisulfite conversion. This inversion simplifies the design process because the probes target the actual methylation mark rather than relying on conversion efficiency and ratio, eliminating the complexity of primer design and improving reproducibility.
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 rapid, sensitive, and specific detection of DNA methylation without amplification, reducing errors and improving accuracy by utilizing a one-step process without bisulfite pretreatment.
Implementation Method 1
mixing the PNA probe with a biological sample to hybridize the PNA probe with a target gene included in the biological sample
Implementation Method 2
applying heat to the resulting mixture at a temperature higher than a melting temperature (Tm) of a hybrid of a non-methylated gene and the PNA probe
Data Source
AI summary
The present invention relates to a modified PNA oligomer for detecting gene methylation. By using a PNA probe modified by introducing a methyl group-specific substituent to the gamma position, N-terminus or C-terminus of the PNA, the present invention may be used for a method for detecting using a difference in physical properties between a gene and a non-methylated gene caused by an interaction between the probe and methyl groups of the gene.