Methylated DNA Detection via Droplet Partitioning
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Solution Overview
Problem
Current methods for detecting DNA and genetic variations, particularly fetal DNA in maternal plasma, face challenges due to low concentrations and interference from maternal DNA, making it difficult to differentiate between euploid and aneuploid fetuses or detect genetic variations like SNPs effectively.
Innovation Solution
A method involving contacting a DNA sample with a methylation-sensitive reagent, partitioning it into spatially-isolated droplets, and detecting hypermethylated loci such as RASSFlA, CASP8, or SCGB3A1 to quantify methylated DNA, which allows for the differentiation of fetal DNA from maternal DNA and the detection of genetic variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DNA detection methods are used to detect fetal DNA in maternal plasma, then the detection can be performed, but the sensitivity is insufficient due to low fetal DNA concentration and interference from maternal DNA
Solution Approach 1:
The DNA sample is partitioned into numerous spatially-isolated droplets, creating independent reaction compartments. This segmentation allows each droplet to contain at most one fetal DNA template molecule, enabling single-molecule detection and eliminating competitive inhibition from maternal DNA. The partitioning transforms a homogeneous mixture into discrete units that can be individually analyzed.
Solution Approach 2:
The invention extracts and detects specific methylated DNA sequences that are unique to fetal origin. By using methylation-sensitive reagents that specifically recognize and bind to methylated cytosine residues in fetal DNA sequences (such as RASSF1A, CASP8, or SCGB3A1), the method selectively isolates fetal DNA signals from the overwhelming maternal DNA background.
2Measurement precision
If invasive testing methods like amniocentesis or CVS are used for prenatal diagnosis, then accurate fetal DNA detection is achieved, but there is a procedure-related risk of pregnancy loss
Solution Approach 1:
The invention uses maternal plasma as an intermediary medium to access fetal DNA without direct invasion of the fetal environment. Fetal DNA naturally circulates in maternal plasma throughout pregnancy, providing a non-invasive window into fetal genetics. This intermediary approach eliminates the need for physical penetration of the amniotic sac or placenta, thereby avoiding procedure-related risks while still enabling fetal genetic analysis.
3Measurement precision
If the DNA sample is partitioned into spatially-isolated droplets, then detection sensitivity is enhanced, but the device complexity increases
Solution Approach 1:
The droplet partitioning system is designed to self-assemble and self-maintain through simple physical processes. Once droplets are generated, they naturally remain spatially isolated due to surface tension and hydrophobic effects, requiring no active control mechanisms. The system uses passive digital PCR where thermal cycling uniformly affects all droplets simultaneously, eliminating the need for individual droplet manipulation and reducing overall system complexity.
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 method significantly enhances the sensitivity for detecting and quantifying methylated DNA, enabling accurate differentiation of fetal DNA from maternal DNA and improved detection of genetic variations, potentially reducing the risk of pregnancy complications and improving prenatal diagnosis.
Implementation Method 1
contacting a DNA sample with a methylation-sensitive reagent
Implementation Method 2
partitioning said DNA sample into a plurality of spatially-isolated partitions; said spatially-isolated partitions are emulsified droplets
Data Source
AI summary
The present disclosure provides methods and compositions for detecting polynucleotides in a sample and for quantifying polynucleotide load in a sample. The polynucleotides can be associated with a disease, disorder, or condition. In some applications, methylated DNA is quantified, e.g., in order to determine the load of polynucleotides in a sample. The present disclosure also provides methods and compositions for determining the load of fetal polynucleotides in a biological sample, e.g., the load of fetal polynucleotides (e.g., DNA, RNA) in maternal plasma. The present disclosure provides methods and compositions for detecting cellular processes such as cellular viability, growth rates, and infection rates. This disclosure also provides compositions and methods for detecting differences in copy number of a target polynucleotide. In some embodiments, the methods and compositions provided herein are useful for diagnosis of fetal genetic abnormalities, when the starting sample is maternal tissue (e.g., blood, plasma). The methods and materials described apply techniques for allowing detection of small, but statistically significant, differences in polynucleotide copy number.