Emulsion Multiple Displacement Amplification for Genome Coverage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current whole genome amplification methods, such as PEP and DOP-PCR, face challenges with incomplete genome coverage, especially in small DNA samples, and Phi29 polymerase-based multiple displacement amplification (MDA) suffers from background DNA synthesis and poor representation at low template concentrations.
Innovation Solution
The method involves performing multiple displacement amplification reactions in an emulsion format with a reaction mixture containing oligonucleotide primers, polymerase enzymes, and an emulsion-forming component like non-ionic detergents, along with stabilizing agents like betaine and trehalose, to enhance representation and allelic balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Phi29 polymerase-based multiple displacement amplification is used to amplify small DNA samples, then amplification efficiency is improved, but background DNA synthesis and poor representation occur
Solution Approach 1:
The reaction mixture is segmented into discrete water-in-oil emulsion droplets, each containing a template DNA molecule and necessary reagents. This physical segmentation isolates individual amplification reactions, preventing background synthesis from interfering with template-specific amplification and improving representation accuracy.
Solution Approach 2:
An emulsion system acts as an intermediary between the polymerase enzyme and the template DNA. The emulsion droplets create a controlled microenvironment that enhances specific amplification while suppressing non-specific background DNA synthesis, resolving the contradiction between efficiency and representation.
2Speed
If conventional PCR-based whole genome amplification methods are used, then amplification speed is improved, but incomplete genome coverage occurs
Solution Approach 1:
The invention changes the fundamental reaction parameters from cyclic thermal PCR to isothermal conditions within emulsion droplets. This parameter change enables continuous strand-displacement synthesis by Phi29 polymerase, achieving both rapid amplification and complete genome coverage without the limitations of conventional PCR methods.
Solution Approach 2:
The invention replaces the thermal cycling mechanical system of conventional PCR with a chemical-biological strand-displacement mechanism. Phi29 polymerase continuously synthesizes DNA at constant temperature, displacing newly synthesized strands to create templates for further amplification, thereby achieving complete genome coverage without thermal denaturation cycles.
3Adaptability or versatility
If random hexamers are used for priming in MDA, then amplification breadth is improved, but background synthesis increases at low template concentrations
Solution Approach 1:
Random hexamer priming is performed within segmented emulsion droplets, where each droplet contains limited reagents and a specific template. This segmentation restricts background synthesis to individual droplets while maintaining the broad priming capability of random hexamers, effectively reducing overall background noise.
Solution Approach 2:
The emulsion system creates local quality differences between the interior (aqueous phase with template and reagents) and exterior (oil phase). Random hexamers can prime throughout the genome within each droplet, but background synthesis is confined to local droplet environments, preventing widespread non-specific amplification.
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 improves the sensitivity and allelic balance of DNA amplification, allowing for efficient amplification of small DNA samples while minimizing interference from background nucleic acids, thereby maintaining the genetic representation of the original template.
Implementation Method 1
The reaction can be catalyzed by enzymes such as the Phi29 DNA polymerase or the large fragment of the Bst DNA polymerase
Implementation Method 2
performing multiple displacement amplification reactions in an emulsion format with a reaction mixture containing oligonucleotide primers, polymerase enzymes, and an emulsion-forming component like non-ionic detergents
Implementation Method 3
Multiple displacement amplification (MDA, is a non-PCR-based isothermal method based on the annealing of random hexamers to denatured DNA, followed by strand-displacement synthesis at constant temperature
Data Source
AI summary
The present invention provides methods kits and systems for performing multiple displacement amplification reactions. In one method a sample of nucleic acid is provided. The nucleic acid is contacted with a reaction mixture which includes a set of oligonucleotide primers, a one or more polymerase enzymes and a detergent. The reaction mixture is then subjected to conditions under which the nucleic acid sequence is amplified to produce an amplified product in a multiple displacement reaction. The method may also be carried out by contacting the nucleic acid with the reaction mixture in the form of an emulsion. A kit is also provided for carrying out either the methods described above. The kit includes one or more polymerases, a plurality of primers and a detergent. The kit may also include a hydrophobic polymer and may include instructions for performing a multiple displacement amplification reaction on a nucleic acid sample.