Isothermal Whole Genome Amplification Reducing Allele Dropout
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Solution Overview
Problem
Current isothermal whole genome amplification protocols face challenges with single cell samples, experiencing high allele and locus dropout rates, amplification bias, and genetic material damage, particularly when dealing with low levels of genomic material or blood samples, which often require extensive purification and result in undesirable outcomes.
Innovation Solution
The method involves preparing a lysis mixture with oligonucleotides and a lysis buffer for cell lysis, followed by neutralization and the addition of oligonucleotide primers for amplification, conducted under isothermal conditions without heat denaturation, using optimized buffers and reagents like Phi29 DNA polymerase and BSA to maintain DNA integrity and reduce template-independent polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard isothermal WGA protocols are used with single cell genomic material, then amplification can be performed, but high allele dropout and locus dropout rates occur
Solution Approach 1:
The patent modifies the chemical composition of the lysis buffer by adding a reducing agent (beta-mercaptoethanol) and adjusting pH conditions to create optimal conditions for single cell WGA, thereby reducing allele dropout while maintaining amplification efficiency
Solution Approach 2:
The patent introduces an intermediary step of cell lysis with protective agents before WGA amplification. The lysis buffer containing reducing agents and pH modifiers serves as a protective intermediary that preserves genomic integrity during the transition from single cell to amplified product
2Ease of operation
If standard cell lysis conditions are performed prior to WGA, then cells can be lysed, but damage (nicking, breaking, and/or fragmenting) of genetic material occurs
Solution Approach 1:
The patent converts the potentially harmful effects of standard lysis conditions into beneficial effects by adding a reducing agent that prevents oxidative damage to DNA while maintaining cell lysis efficiency. The modified lysis buffer transforms a harmful process into a protective one
3Reliability
If extensive purification is performed to isolate genomic DNA from whole blood, then red blood cells can be removed, but the process is time-consuming and complex
Solution Approach 1:
The patent extracts and removes the harmful component (heme from red blood cells) through a simplified one-step lysis buffer treatment that selectively eliminates inhibition while preserving target DNA, avoiding the need for extensive multi-step purification protocols
Solution Approach 2:
The modified lysis buffer serves multiple functions simultaneously: it lyses cells, protects DNA from damage, removes heme inhibition, and prepares samples for WGA in a single unified protocol, eliminating the need for separate purification steps
4Productivity
If Phi29 DNA polymerase is used with blood samples containing heme, then amplification can proceed, but strong inhibition occurs resulting in negative results
Solution Approach 1:
The patent converts the harmful effect of heme inhibition into a beneficial outcome by using a reducing agent that chemically modifies heme, transforming it from an inhibitory substance into a non-inhibitory form, thereby enabling successful amplification without purification
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 achieves high-quality, low-bias amplification of genetic material from single cells with reduced dropout rates and improved integrity, enabling efficient analysis through array comparative genomic hybridization and sequencing, even in the presence of red blood cells without prior purification.
Implementation Method 1
incubating the mixture for up to 30 minutes, thereby lysing the cell in the mixture
Implementation Method 2
a lysis buffer solution comprising: a base; and a reducing agent
Implementation Method 3
a polymerase; dNTPs; and incubating the mixture to permit an amplification reaction
Implementation Method 4
where the incubation does not include a heat denaturation step
Implementation Method 5
adding a neutralization solution and an amount of oligonucleotide primers sufficient for amplification of the DNA
Implementation Method 6
heating the neutralized subsamples for less than 2 minutes to denature DNA in the neutralized subsamples
Data Source
AI summary
Disclosed are methods and compositions for amplification of genetic material, including isothermal WGA of single cells.