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OBJECTIVES: The detection of the clinically important genetic markers, including mosaic mutations, is challenging but essential for precise clinical decision making. Next-generation sequencing (NGS) analysis with deep sequence coverage is a reliable approach for detection of genetic variants, including low-level mutations. Here we present usefulness of such approach in the detection of constitutional mosaicism in bilateral choroid plexus carcinoma and glioblastoma. METHODS: Whole exome sequencing of DNA extracted from probands leukocytes was performed on an Illumina HiSeq 1500 using the Nextera Rapid Capture Enrichment Kit (Illumina). The detected variants were validated by NGS deep amplicon sequencing on the Illumina MiSeq in the patient’s DNA extracted from buccal cells, urine sediment samples and tumor samples. RESULTS: NGS analysis revealed constitutional mutations c.742C>T in TP53 in patient with bilateral choroid plexus carcinoma and c.2392T>C in PSM2 in patient with glioblastoma. They were observed in only 12 of 91 (13.2%) and 37 of 116 (32%) sequencing reads, respectively. Identified TP53 substitution was not found in patient’s parents, indicating an apparent de novo mutation. The presence of allelic imbalance in samples from buccal cells and urine sediment supports the occurrence of constitutional mosaicism. Importantly, TP53 variant was undetectable when Sanger sequencing was applied. CONCLUSION: Our results highlight the utility of the NGS technology in the detection of mosaic mutations which may not be detectable by Sanger sequencing. This may be important for management of patients and genetic counseling, including a predisposition to other cancers. Funded by National Science Centre, Poland (2016/23/B/NZ2/03064 and 2016/21/B/NZ2/01785) |
