Blocking Oligonucleotides for Allele-Specific Amplification
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Solution Overview
Problem
Current allele-specific amplification methods face challenges in achieving high sensitivity and specificity for clinically relevant nucleic acid targets, particularly in distinguishing between wild type and mutant sequences during PCR, as they often allow for detectable amplification of undesired variants.
Innovation Solution
A method utilizing a blocking oligonucleotide with a covalently modified base at the exocyclic amino group, which is perfectly complementary to the wild type sequence but partially non-complementary to the mutant sequence, forming complexes with different melting temperatures, and is blocked at the 3′ terminus to inhibit extension, using a polymerase lacking 5′-3′ nuclease activity to selectively amplify the target sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a blocking oligonucleotide is designed to be perfectly complementary to wild type sequence, then specificity for wild type suppression is improved, but amplification of wild type sequence cannot be completely inhibited due to detectable levels of undesired variant amplification
Solution Approach 1:
The blocking oligonucleotide incorporates a modified base at a specific local position (exocyclic amino group) to enhance its binding affinity and stability with the wild type sequence. This localized modification creates a differential binding effect where the blocking oligonucleotide strongly suppresses wild type amplification while having minimal impact on mutant sequence amplification, thereby resolving the contradiction between specificity and inhibition effectiveness.
2Measurement precision
If amplification temperature is increased to improve mutant sequence amplification, then sensitivity for mutant detection is improved, but wild type sequence suppression becomes less effective
Solution Approach 1:
The invention utilizes the modified base in the blocking oligonucleotide to create a stable hybrid with the wild type sequence that maintains suppression effectiveness across a range of amplification temperatures. The modified base enhances the thermal stability of the blocking oligonucleotide-wild type complex, allowing effective wild type suppression even at higher temperatures where mutant sequence amplification is optimized, thus resolving the temperature-related contradiction.
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 enhances the specificity and sensitivity of allele-specific amplification by selectively inhibiting the amplification of wild type sequences while allowing efficient amplification of mutant sequences, even when present in variant forms, by destabilizing the hybrid with the mutant sequence during PCR.
Implementation Method 1
the blocking oligonucleotide being perfectly complementary to a wild type (WT) sequence when hybridized forming a first complex having a first melting temperature (Tm), the blocking oligonucleotide being partially non-complementary, at one or more nucleotides, to a target mutant (MT) sequence when hybridized forming a second complex having a second melting temperature (Tm)
Implementation Method 2
at least one nucleotide with a base covalently modified at the exocyclic amino group
Implementation Method 3
performing an amplifying step at a temperature higher than the second Tm but lower than the first Tm utilizing a polymerase lacking 5′-3′ nuclease activity, the amplifying step comprising contacting the sample with a set of primers to produce an amplification product
Data Source
AI summary
A method is provided for allele-specific amplification, utilizing a blocking oligonucleotide including at least one nucleotide with a base covalently modified at the exocyclic amino group, the blocking oligonucleotide being perfectly complementary to a wild type (WT) sequence when hybridized forming a first complex having a first melting temperature (Tm), the blocking oligonucleotide being partially non-complementary, at one or more nucleotides, to a target mutant (MT) sequence when hybridized forming a second complex having a second melting temperature (Tm), wherein the first Tm is higher than the second Tm and having at least one nucleotide with a base covalently modified at the exocyclic amino group, wherein the blocking oligonucleotide becomes unhybridized from the target MT sequence during amplification but remains hybridized with the WT sequence inhibiting amplification of the WT sequence utilizing a polymerase lacking 5′-3′ nuclease activity.