Stem-loop RT Oligonucleotide for miRNA Detection
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Solution Overview
Problem
Current methods for detecting microRNAs (miRNAs) face challenges such as low assay sensitivity, poor discrimination among homologs, and high costs due to the need for multiple processing steps and fluorescent probes, especially with the increasing number of miRNA candidates identified.
Innovation Solution
A method using a combination of reverse transcription (RT) and polymerase chain reaction (PCR) amplification with modified stem-loop RT oligonucleotides and hemi-nested PCR primers to specifically identify target miRNAs, reducing mis-priming and allowing for rapid, multiplexed detection without RNA isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TaqMan probe-based real-time RT-PCR is used for miRNA detection, then sensitivity and specificity are improved, but assay complexity and cost increase due to additional probe hydrolysis step
Solution Approach 1:
The patent extracts the fluorescent probe detection step from the RT-PCR assay, using only PCR primers for amplification and detection. The method uses a stem-loop RT primer that incorporates a blocking modification to prevent PCR amplification of the RT primer itself, eliminating the need for TaqMan probes while maintaining detection sensitivity and specificity through standard PCR amplification of the cDNA product.
Solution Approach 2:
The patent makes the RT primer serve multiple functions: it performs reverse transcription of the miRNA target and simultaneously acts as a template for PCR amplification after the blocking modification is removed. This multi-functional design eliminates the need for separate probe molecules, reducing assay complexity while maintaining detection capabilities.
2Adaptability or versatility
If multiple miRNA candidates are detected using deep sequencing identification, then detection versatility is improved, but design and cost of TaqMan probes for each miRNA becomes prohibitive
Solution Approach 1:
The patent employs a universal RT primer design with a common stem-loop structure that can be adapted to detect multiple different miRNA candidates by simply changing the loop sequence. This universal approach allows high-throughput detection of numerous miRNA candidates without requiring individual TaqMan probe design for each target, significantly reducing assay design complexity and cost while maintaining detection versatility.
3Productivity
If fast thermo-cycling protocols are used for rapid miRNA detection, then productivity is improved, but compatibility with TaqMan assays is lost due to probe hydrolysis requirements
Solution Approach 1:
The patent removes the TaqMan probe hydrolysis step from the assay, enabling compatibility with fast thermo-cycling protocols. By using standard PCR amplification without probe-based detection, the method can utilize rapid cycling conditions that shorten amplification time while maintaining reliable detection through the blocking modification strategy on the RT primer.
4Measurement precision
If RNA isolation steps are included in miRNA detection, then measurement precision is improved, but loss of time and operational complexity increase
Solution Approach 1:
The patent performs reverse transcription directly on the isolated miRNA without requiring extensive RNA purification or isolation steps. The stem-loop RT primer design allows specific binding and reverse transcription of miRNA even in crude samples, enabling detection with minimal sample preparation time while maintaining detection accuracy through the specific stem-loop structure that prevents mis-priming.
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 provides specific and rapid detection of miRNAs, retaining sensitivity and specificity even with fast thermo-cycling, and is economical, high-performance, easy to use, and capable of direct detection from cell lysates, reducing the need for laborious RNA isolation.
Implementation Method 1
reverse transcribing the target miRNA contained in the sample using an RT oligonucleotide to produce a reverse transcription product
Implementation Method 2
amplifying the reverse transcription product using primers to produce an amplification product
Implementation Method 3
wherein the stem-loop portion adopts a stem-loop structure under conditions used for said reverse transcribing but does not adopt the stem-loop structure under conditions used for said amplifying
Data Source
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AI summary
There is provided a method for detecting a target RNA molecule in a sample. The method comprises reverse transcribing the target RNA contained in the sample using an RT oligonucleotide, the RT oligonucleotide comprising a stem-loop portion containing one or more nucleotides modified or modifiable to block DNA polymerase extension and a target annealing portion that is complementary to a downstream portion of the target RNA, the target annealing portion located 3 ' to the stem-loop portion, to produce a reverse transcription product that comprises the RT oligonucleotide and a 3 ' extended region; amplifying the reverse transcription product using (i) a first amplification primer that anneals to a downstream portion of the 3 ' extended region of the reverse transcription product and (ii) a second amplification primer that anneals to an interface portion of a DNA strand complementary to the reverse transcription product, the interface portion comprising a region that is complementary to a 3' portion of the RT oligonucleotide and a 5' portion of the 3' extended region in the reverse transcription product, to produce an amplification product; and detecting the amplification product; wherein the stem-loop portion adopts a stem-loop structure under conditions used for said reverse transcribing but does not adopt the stem-loop structure under conditions used for said amplifying and wherein when the stem-loop portion contains one or more nucleotides that are modifiable to block DNA polymerase extension, the method further comprises modifying the modifiable nucleotide prior to said amplifying.