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Molecular Diagnostics and Genetics |
1 Armed Forces Radiobiology Research Institute, Biological Dosimetry Team, 8901 Wisconsin Ave., Bethesda, MD 20889-5603.
2 Bio-Rad Laboratories Headquarters, 1000 Alfred Nobel Dr., Hercules, CA 94547
aAuthor for correspondence. Fax 301-295-6503; e-mail grace{at}afrri.usuhs.mil.
Background: High-throughput and forward-deployable biological dosimetry capabilities are required for tactical and medical decisions after radiologic events. We previously reported a quantitative reverse transcription (QRT)-PCR assay for human radiation-responsive gene targets using a whole-blood ex vivo irradiation model, but we needed a multitarget assay on a smaller, less costly, real-time PCR detection system.
Methods: We developed a quadruplex QRT-PCR assay in a 96-well, closed-plate format suitable for use with RNA extracted from whole blood. Four cDNA targets were simultaneously amplified in a sealed tube by hybridization to exonuclease probes, each conjugated to distinct fluorogenic reporters. A novel primer-limited 18S rRNA reference target was validated from serial dilutions of human total RNA. To test assay precision, we incorporated a positive-control cDNA mimic into duplex and quadruplex PCR reactions. The master mixture was supplemented with more enzyme, MgCl2, and deoxyribonucleotides. Simultaneous detection of four targets was evaluated in comparison with respective duplex QRT-PCR assays.
Results: The simultaneous detection of three radiation-responsive genes by quadruplex QRT-PCR was quantitative, with gene expression changes similar to those observed with optimized duplex and triplex QRT-PCR assays. The 18S rRNA and GADD45 calibration curves (threshold cycle vs log10 cDNA) were linear and reproducible and showed optimal PCR efficiencies as indicated by slopes statistically equivalent to the theoretical value of -3.322.
Conclusions: This is the first study of a quadruplex QRT-PCR assay. Our approach has diagnostic utility in the detection of biomarkers, biological and toxicologic agents, and genes of inherited diseases and cancer.
The following articles in journals at HighWire Press have cited this article:
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S. Ogino, T. Kawasaki, M. Brahmandam, M. Cantor, G. J. Kirkner, D. Spiegelman, G. M. Makrigiorgos, D. J. Weisenberger, P. W. Laird, M. Loda, et al. Precision and Performance Characteristics of Bisulfite Conversion and Real-Time PCR (MethyLight) for Quantitative DNA Methylation Analysis J. Mol. Diagn., May 1, 2006; 8(2): 209 - 217. [Abstract] [Full Text] [PDF] |
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A. Zhang, L. Pastor, Q. Nguyen, Y. Luo, W. Yang, M. Flagella, R. Chavli, S. Bui, C. T. Nguyen, Z. Zheng, et al. Small Interfering RNA and Gene Expression Analysis Using a Multiplex Branched DNA Assay without RNA Purification J Biomol Screen, September 1, 2005; 10(6): 549 - 556. [Abstract] [PDF] |
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S. A. Amundson, M. B. Grace, C. B. McLeland, M. W. Epperly, A. Yeager, Q. Zhan, J. S. Greenberger, and A. J. Fornace Jr. Human In vivo Radiation-Induced Biomarkers: Gene Expression Changes in Radiotherapy Patients Cancer Res., September 15, 2004; 64(18): 6368 - 6371. [Abstract] [Full Text] [PDF] |
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