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RNA-based mutation screening in hereditary nonpolyposis colorectal cancer
M Kohonen-Corish1, V L Ross, W F Doe
1Division of Molecular Medicine, John Curtin School of Medical Research, Australian National University, Canberra. maija.corish@anu.edu.au
American Journal of Human Genetics
|October 1, 1996
Summary
Researchers identified six gene defects in Australian Hereditary Nonpolyposis Colorectal Cancer (HNPCC) families, finding RNA screening methods complicated by alternative transcripts. This impacts the development of accurate diagnostic tests for HNPCC gene mutations.
Area of Science:
- Genetics
- Molecular Biology
- Oncology
Background:
- Hereditary Nonpolyposis Colorectal Cancer (HNPCC) is an autosomal dominant cancer syndrome.
- Four known susceptibility genes encode DNA mismatch repair enzymes.
- Identifying gene defects is crucial for diagnosis and management.
Purpose of the Study:
- To identify HNPCC gene defects in Australian families.
- To evaluate the efficacy of RNA-based screening methods for HNPCC mutations.
- To analyze the impact of alternative transcripts on mutation detection.
Main Methods:
- Combination of DNA-based and RNA-based mutation detection.
- Reverse-transcriptase polymerase chain reaction (RT-PCR) for transcript analysis.
- Protein-truncation testing for functional assessment.
Main Results:
- Six mutations identified: four in hMLH1 and two in hMSH2.
- Five mutations predicted to cause truncated proteins, including a splice-site mutation.
- RNA-based screening was confounded by numerous alternative hMLH1 transcripts, especially in whole blood samples.
- Distinguishing pathogenic mutations from benign variants was challenging due to transcript variability.
Conclusions:
- The study identified specific HNPCC gene mutations in an Australian cohort.
- Alternative splicing and transcript variants significantly complicate RNA-based screening for HNPCC.
- Findings have critical implications for designing reliable diagnostic tests for HNPCC gene defects.