TPMT Mutation Detection via Primer Extension
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Solution Overview
Problem
Current methods for determining TPMT activity levels in individuals before thiopurine therapy are inadequate, leading to potential serious side effects due to genetic variations in the TPMT gene, which affect enzyme activity.
Innovation Solution
A method involving single nucleotide primer extension is used to detect specific mutations (G238C, G460A, and A719G) in the TPMT gene by amplifying relevant regions and using labeled dNTPs to identify mutations, indicating reduced TPMT activity and susceptibility to thiopurine drug toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current methods for determining TPMT activity levels are used, then the assessment process is simple, but the reliability of identifying genetic variations and preventing side effects is insufficient
Solution Approach 1:
The TPMT gene detection is segmented into three specific mutation sites (G238C, G460A, A719G), with each site analyzed independently through specific primer extension reactions. This segmentation allows reliable identification of each mutation while maintaining a manageable assay structure by focusing on critical regions rather than the entire gene sequence.
Solution Approach 2:
The method performs preliminary amplification of specific TPMT gene regions containing mutation sites before the actual detection step. By pre-amplifying only the relevant segments (exons 5, 7, and 10), the assay prepares the necessary targets in advance, ensuring reliable detection while reducing the complexity of analyzing the entire 34 kb gene.
2Loss of information
If the entire TPMT gene is analyzed, then complete genetic information is obtained, but the time and resources required for analysis increase significantly
Solution Approach 1:
The method extracts and analyzes only the critical mutation sites (G238C in exon 5, G460A in exon 7, and A719G in exon 10) from the entire TPMT gene. By taking out only these specific regions for amplification and analysis, the assay obtains sufficient genetic information to determine TPMT activity status without the time-consuming analysis of the complete 34 kb gene sequence.
Solution Approach 2:
The assay applies local quality analysis by focusing detection resources on specific high-value regions containing known pathogenic mutations. Instead of uniform analysis across the entire gene, the method concentrates amplification and primer extension efforts on exons 5, 7, and 10 where the critical mutations are located, thereby achieving accurate genotype determination with reduced time and resource investment.
3Adaptability or versatility
If multiple mutations are detected simultaneously, then comprehensive genotype determination is achieved, but the complexity of the detection system increases
Solution Approach 1:
The detection system achieves universality by using a common amplification and detection framework that can identify all three mutations (G238C, G460A, A719G) through a unified primer extension approach. Each mutation is detected using specific primers and labeled ddNTPs within the same assay platform, allowing comprehensive genotype determination without requiring separate specialized systems for each mutation.
Solution Approach 2:
The method merges the detection of three separate mutations into a single integrated assay. By combining the amplification of multiple exons and the primer extension detection of three different mutation sites into one cohesive protocol, the system achieves versatile multi-mutation detection while managing complexity through standardized procedures and reagents across all detection channels.
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 effectively identifies individuals with reduced TPMT activity, allowing for pre-therapeutic assessment and prevention of adverse reactions by correlating mutations with enzyme activity levels.
Implementation Method 1
a DNA polymerase, and iv) a labeled ddNTP corresponding to the nucleotide representing the mutation, under conditions wherein, in the presence of an amplified region containing the mutation, the labeled ddNTP is added to the 3'-end of the primer to generate a labeled extension primer
Implementation Method 2
an extension primer complementary to the amplified region, wherein the 3'-end base of the primer is positioned one base 5' to the point mutation site when the primer is hybridized to the amplified region
Implementation Method 3
amplifying a region of the TPMT gene containing the site of the mutation to create an amplified region
Data Source
AI summary
Methods and compositions are described for use in the rapid and simultaneous screening of one or more samples for one or more mutations in the TPMT gene. The methods and compositions of the present invention can be used to rapidly determine if a mutation of the TPMT gene is present in the genome of a subject. Identifying which mutations are present in an individual allows the clinician to design an appropriate therapy using drugs metabolized by TPMT for that individual.