Molecular Inversion Probes for Accurate Telomere Length Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring telomere length, such as telomere restriction fragment assays and real-time quantitative PCR, are inaccurate and unreliable due to their limitations in handling large DNA samples and being prone to variations in equipment and software quality, and are not suitable for tandem repeat sequences like telomeres, which require new, reliable methods for epidemiological studies and routine laboratory use.
Innovation Solution
The development of single-stranded DNA probes with 5′ and 3′ homology regions that bind to the same strand of a template DNA, allowing for the determination of telomere length by quantifying circularized and ligated linear probe products using a kit with DNA polymerase and ligase activity, without the need for exonuclease enzymes, to accurately assess tandem repeat sequences like telomeres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If classical MIP-based methods are used to measure tandem repeat sequences, then the method can be applied to telomere length measurement, but the results are highly inaccurate and unreliable due to promiscuous binding of MIP ends to multiple repeats
Solution Approach 1:
The probe is divided into distinct functional segments: a 5′ homology region, a 3′ homology region, and a linker region. The homology regions are designed to bind to specific repeat units while the linker region contains a gap that must be filled by DNA polymerase, ensuring that ligation occurs only within a single repeat unit rather than allowing promiscuous binding across multiple repeats.
Solution Approach 2:
DNA polymerase is introduced as an intermediary enzyme that fills the gap in the linker region between the 5′ and 3′ homology regions. This gap-filling step serves as a mediator that ensures proper positioning and alignment of the probe ends before ligation, preventing incorrect binding to multiple repeat units and enabling accurate measurement of tandem repeat sequences.
2Measurement precision
If classical MIP-based assays remove all linear products prior to detection, then non-specific MIPs are removed, but accurate quantification of tandem repeat sequences becomes impossible due to loss of ligation point information
Solution Approach 1:
Instead of removing all linear products, the method extracts and retains only the ligated linear products that contain the probe sequence. This selective extraction preserves the ligation point information needed for accurate quantification while eliminating non-specific MIPs through the design of the homology regions that specifically target tandem repeat sequences.
Solution Approach 2:
The probe design incorporates a gap in the linker region that requires gap-filling by DNA polymerase before ligation can occur. This preliminary gap-filling action ensures that only properly positioned probe ends are ligated, creating a distinct ligated product that can be specifically detected and quantified without interference from non-ligated MIPs.
3Quantity of substance
If telomere restriction fragment assays are used to measure telomere length, then the method can handle large DNA samples, but the results are affected by gel electrophoresis variations and image capturing quality
Solution Approach 1:
The method replaces the mechanical gel electrophoresis and image capture system with a molecular biology-based detection system using ligated linear probe products. Instead of separating DNA fragments by size through electrophoresis and capturing images, the method uses specific ligation reactions followed by quantitative PCR or sequencing to determine telomere length, eliminating variability introduced by gel electrophoresis and image quality.
Solution Approach 2:
The detection method changes from measuring physical fragment size via electrophoresis to quantifying the amount of ligated probe products through molecular amplification and sequencing. This parameter change from physical dimension measurement to molecular quantity measurement provides more consistent and reproducible results that are not affected by gel electrophoresis variations or image capturing quality.
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 provides a reliable and accurate method for determining telomere length and tandem repeat sequences, overcoming the limitations of existing techniques by ensuring precise quantification of ligation points, which correlates with telomere length, and is applicable for large-scale studies and routine laboratory practices.
Implementation Method 1
the 5′ and 3′ ends of the MIPs directed to tandem repeat sequences would necessarily target the same, repeated sequence, such probes are not suitable for traditional MIP-based methods because they would permit promiscuous binding of the MIP ends to any of the numerous repeats within a given repeat array
Implementation Method 2
the nucleotide gap of less than one complete repeat unit comprises at most 2 different bases
Implementation Method 3
allowing their circularization following 3′ end extension (also known as 'gap filling') and subsequent ligation
Data Source
AI summary
The present invention provides novel compositions and methods for assessing the size of tandem repeat sequences, e.g., telomeres, within a genome, using specially designed Molecular Inversion Probes (MIPs) and reaction conditions.