Subpopulation Genomic DNA Methylation Detection via Chromatin Segmentation
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Solution Overview
Problem
Current methods are inadequate for accurately determining the methylation status of genomic DNA in a biological sample, particularly in identifying cancerous cells within a mixture of healthy cells, due to limitations in distinguishing between accessible and inaccessible chromatin regions.
Innovation Solution
The method involves dividing a biological sample into portions, enriching a subpopulation of genomic DNA, and determining DNA methylation status at specific regions to identify differences indicative of cancerous cells, using techniques such as chromatin immunoprecipitation (ChIP) and bisulfite modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methylation detection methods are used on total genomic DNA, then the detection can be performed on the entire sample, but the sensitivity to detect cancerous cells in small proportions is insufficient
Solution Approach 1:
The method segments genomic DNA into two distinct populations based on chromatin accessibility: accessible gDNA (enriched for cancerous cells) and inaccessible gDNA (enriched for healthy cells). This segmentation is achieved through differential extraction where accessible chromatin is isolated first, allowing the detection method to focus on the relevant cancerous cell population and dramatically improving detection sensitivity even when cancerous cells are present in small proportions.
Solution Approach 2:
The method applies different extraction conditions to different chromatin regions. Accessible chromatin regions (associated with cancerous cells) are extracted under conditions that preserve their open structure, while inaccessible chromatin regions (associated with healthy cells) remain bound to nuclei. This local quality differentiation allows selective analysis of cancerous cell DNA without being masked by the abundant healthy cell DNA.
2Measurement precision
If chromatin is tightly packaged in heterochromatin, then DNA is protected and stable, but DNA methylation status cannot be accurately determined
Solution Approach 1:
The method performs preliminary extraction of accessible chromatin before analyzing methylation status. By first isolating the accessible gDNA population under controlled conditions that maintain chromatin structure, the method ensures that subsequent methylation analysis is performed on DNA that is already in a detectable state, eliminating the need to disrupt chromatin structure and preserving the accuracy of methylation status determination.
Solution Approach 2:
The method uses chromatin accessibility as an intermediary property to identify and isolate cancerous cell DNA. Instead of directly analyzing methylation in tightly packaged heterochromatin, the method first exploits the differential accessibility of chromatin from cancerous versus healthy cells as a mediator to enrich for cancerous cell DNA, making subsequent methylation analysis accurate and reliable.
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 allows for the sensitive detection of cancerous cells by highlighting methylation differences in enriched DNA populations, enabling the identification of cancerous cells within a background of healthy cells, even when present in small proportions.
Implementation Method 1
enriching for inaccessible gDNA in the first portion
Implementation Method 2
using techniques such as chromatin immunoprecipitation (ChIP) and bisulfite modification
Data Source
AI summary
This invention provides methods of determining the biological, pathological, genetic, epigenetic or disease status in a biological sample by determining the methylation status of a subpopulation of genomic DNA in the sample.