Single-Cell Genome Methylation and Variant Analysis via Deamination and PTA
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting genome variants and methylation in single cells are limited by poor genome recovery and high false positive rates, making it difficult to accurately study the connection between altered cell states and somatic genetic alterations.
Innovation Solution
A method involving deamination of genomic DNA to convert cytosines to uracil and modified cytosines to thymine, followed by uracil removal and amplification using Primary Template-Directed Amplification (PTA), enabling concurrent detection of methylation and genomic variants in the same cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used for detecting genome variants and methylation in single cells, then detection capability is provided, but genome recovery is poor and false positive rates are high
Solution Approach 1:
The method segments the detection process into distinct stages: (1) deamination treatment to convert cytosines to uracils and modified cytosines to thymidines, (2) selective uracil removal using uracil-DNA glycosylase, (3) primary template-directed amplification, and (4) sequencing. This segmentation allows each step to be optimized independently, improving overall detection accuracy while preserving genome integrity.
Solution Approach 2:
The method performs preliminary deamination treatment before amplification and sequencing. By converting cytosines to uracils and modified cytosines to thymidines in advance, and subsequently removing uracils, the method prepares the DNA in a state that enables accurate distinction between modified and unmodified cytosines during sequencing, thereby improving detection accuracy without compromising genome recovery.
2Quantity of substance
If conventional amplification methods are used, then genome DNA can be amplified, but error rates increase affecting variant detection accuracy
Solution Approach 1:
The method introduces uracil-DNA glycosylase as an intermediary enzyme that selectively removes uracils from the deaminated DNA before amplification. This intermediary step eliminates uracil-containing sequences that would otherwise be misread as variants during sequencing, thereby preserving the accuracy of somatic variant detection while still enabling sufficient DNA amplification for single-cell analysis.
Solution Approach 2:
The method changes the chemical state of cytosines through deamination (converting them to uracils) and modified cytosines (converting them to thymidines) before amplification. This parameter change creates a distinguishable signature that allows accurate identification of methylation status and somatic variants during sequencing, improving measurement precision while maintaining adequate DNA quantity for analysis.
3Measurement precision
If deamination treatment is applied to detect methylation, then methylation status can be identified, but cytosine conversion to uracil creates background noise for variant calling
Solution Approach 1:
The method converts the harmful effect of uracil formation (which creates background noise for variant calling) into a beneficial feature by using uracil-DNA glycosylase to selectively remove uracils. This conversion transforms the deamination process from a source of false positives into a reliable methylation detection mechanism, as the removed uracils are replaced during amplification, leaving no trace in the final sequencing data.
Solution Approach 2:
The method extracts and removes uracils from the deaminated DNA using uracil-DNA glycosylase before amplification. By taking out the harmful uracil components that would otherwise create false positive variants during sequencing, the method preserves the methylation detection capability (since modified cytosines are converted to thymidines, not uracils) while eliminating the source of detection errors.
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
The method achieves over 90% genome recovery with low error rates, allowing for accurate detection of small genomic variants, copy number alterations, and methylation status of regulatory regions in single cells.
Implementation Method 1
contacting the isolated genomic DNA under conditions resulting in deamination of the genomic DNA thereby converting at least some of the cytosines in the genomic DNA to uracil and at least some of the modified cytosines to thymine
Implementation Method 2
contacting the deaminated, isolated the genomic DNA with an enzyme to remove uracil from the genomic DNA
Data Source
AI summary
Provided herein is a method of identifying modified cytosines in genomic DNA in a biological sample. The method includes isolating, from the biological sample, nucleic acids comprising genomic DNA comprising cytosines and modified cytosines, contacting the isolated genomic DNA under conditions resulting in deamination of the genomic DNA thereby converting at least some of the cytosines in the genomic DNA to uracil and at least some of the modified cytosines to thymine, contacting the deaminated, isolated the genomic DNA with an enzyme to remove uracil from the genomic DNA, amplifying the genomic DNA lacking uracil using primary-directed template amplification, and sequencing the genomic DNA, wherein the sequencing identifies the modified cytosines in the genomic DNA of the single cell.