Competitive Hybridization Assays for Microsatellite Instability Detection
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Solution Overview
Problem
Existing amplification assays for target sequences containing repetitive microsatellite sequences face inefficiencies, low signal, and high background, making it difficult to distinguish between normal and mutant alleles, particularly those with altered repetitive sequences.
Innovation Solution
The use of competitive hybridization between a competitor and a probe/primer with a normal and mutant allele of a microsatellite locus, where the competitor outcompetes the probe/primer for hybridization based on the extent of sequence overlap, allowing for the detection of mutant alleles through enumeration of isolated volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional amplification assays are used for target sequences containing repetitive microsatellite sequences, then amplification can be performed, but the assays suffer from inefficient target sequence amplification, low signal, and high background
Solution Approach 1:
A competitor oligonucleotide is introduced as an intermediary element that competes with the probe for hybridization to the normal allele. This competitor acts as a mediator to enhance the discrimination between normal and mutant alleles by outcompeting the probe for normal allele binding, thereby reducing background signal and improving signal quality for mutant detection
Solution Approach 2:
The assay modifies the hybridization parameters by introducing a competitor with specific sequence characteristics that give it higher affinity for the normal allele. By changing the competitive binding parameters and optimizing the competitor's sequence overlap with the normal allele, the assay achieves improved amplification efficiency and signal discrimination
2Illumination intensity
If traditional amplification assays are used for target sequences containing repetitive microsatellite sequences, then amplification can be performed, but the assays produce low signal and high background
Solution Approach 1:
The competitor oligonucleotide converts the harmful effect of background noise into a beneficial discriminative signal. By designing the competitor to specifically outcompete the probe for normal allele binding, the background hybridization is transformed into a useful competitive mechanism that enhances mutant allele detection specificity and reduces false positive background signal
Solution Approach 2:
The competitor serves as an intermediary that mediates between the probe and the normal allele, controlling their interaction. This intermediary element regulates the hybridization equilibrium to favor probe binding only to mutant alleles, thereby reducing background noise while maintaining or enhancing signal intensity for true positive detections
3Measurement precision
If traditional amplification assays are used for target sequences containing repetitive microsatellite sequences, then amplification can be performed, but normal alleles cannot be distinguished from mutant alleles
Solution Approach 1:
The competitor oligonucleotide acts as a discriminatory intermediary that enables differentiation between normal and mutant alleles. By introducing this competitor that specifically targets the normal allele sequence, the assay achieves precise allele discrimination through competitive binding dynamics without requiring complex additional detection systems
Solution Approach 2:
The competitor is designed with local sequence specificity that matches the normal allele's repetitive sequence region. This local quality matching allows the competitor to selectively bind only to normal alleles with the specific repetitive sequence pattern, enabling precise local discrimination between normal and mutant alleles based on their sequence differences
4Measurement precision
If a competitor is introduced to outcompete the probe for normal allele hybridization, then mutant allele detection is improved, but the assay requires additional reagents and steps
Solution Approach 1:
The competitor oligonucleotide is designed to serve multiple functions simultaneously: it competes with the probe for normal allele binding, provides sequence-specific discrimination, and enables mutant allele detection through competitive inhibition. This multi-functionality reduces the need for separate control assays or additional complex procedural steps
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 enables better signal discrimination between amplification-positive and amplification-negative volumes, reduces background noise, and allows for the detection of a range of deletion sizes in repetitive sequences with high sensitivity, facilitating the diagnosis of microsatellite instability without electrophoresis or sequencing.
Implementation Method 1
competitive hybridization of a competitor and a probe/primer with a normal allele and one or more mutant alleles of a microsatellite locus
Data Source
AI summary
Methods and compositions for detecting genetic instability using digital amplification assays. The methods may be performed in a set of isolated volumes and generally may involve competitive hybridization of a competitor and a probe/primer with a normal allele and one or more mutant alleles of a microsatellite locus. The competitor may be configured to compete similarly with, or to outcompete, the primer/probe for hybridization with the normal allele. The primer/probe may be configured to outcompete the competitor for hybridization with various mutant alleles of the locus that alter the length of the repetitive sequence by different amounts. Isolated volumes in which the primer/probe outcompetes the competitor may be enumerated, and represent one or more of the mutant alleles. The methods may enable diagnosing microsatellite instability and treating a subject based on the diagnosis.