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A robust method for detecting CHK2/RAD53 mutations in genomic DNA
Nayanta Sodha1, Richard S Houlston, Richard Williams
1Royal Marsden NHS Trust, Surrey, UK. nayanta@icr.ac.uk
Abstract:
While screening for germline CHK2 mutations in cancer cases by heteroduplex CSGE, we observed that additional PCR fragments were generated from the 3' end region of the gene that includes exons 11-14. Direct sequencing of these fragments suggested that homologous loci (possibly pseudogenes) were concomitantly being amplified. Searches of public sequence databases showed that a number of areas of the genome show a high degree of homology to exons 10-14 of the CHK2 gene. The presence of these homologous regions means that standard screening methods for detecting mutations in CHK2, based on PCR of genomic DNA, are prone to error. To circumvent this problem, we have developed a strategy, based on long-range PCR, to screen the functional copy of CHK2. Using this approach it is possible to carry out a comprehensive mutational analysis of CHK2 from genomic DNA.
Insights
Screening for CHK2 mutations can be error-prone due to homologous sequences. A new long-range PCR method accurately analyzes the functional CHK2 gene copy for comprehensive mutation detection.
Area of Science:
- Genetics
- Molecular Biology
- Cancer Research
Background:
- Germline mutations in CHK2 (Checkpoint Kinase 2) are associated with various cancers.
- Standard screening methods for CHK2 mutations, such as heteroduplex CSGE and PCR, can be unreliable.
- Homologous regions in the genome can interfere with accurate mutation detection.
Purpose of the Study:
- To identify the cause of spurious PCR fragments during CHK2 mutation screening.
- To develop a reliable method for comprehensive mutational analysis of the functional CHK2 gene.
Main Methods:
- Heteroduplex CSGE and direct sequencing were used to analyze PCR fragments.
- Public sequence databases were searched for homologous regions to CHK2 exons.
- A novel strategy employing long-range PCR was developed to specifically amplify the functional CHK2 gene.
Main Results:
- Additional PCR fragments were generated from the 3' end of CHK2 (exons 11-14), indicating amplification of homologous loci.
- High homology was found between CHK2 exons 10-14 and other genomic regions.
- The developed long-range PCR method successfully screened the functional CHK2 copy, circumventing amplification errors.
Conclusions:
- Standard PCR-based screening methods for CHK2 mutations are prone to errors due to pseudogene amplification.
- Long-range PCR provides a robust strategy for accurate and comprehensive mutational analysis of the functional CHK2 gene.
- This improved methodology is crucial for reliable genetic screening in cancer diagnostics.