Hereditary syndromes causing colorectal cancer include both polyposis and non-polyposis syndromes. Overlapping phenotypes between the syndromes have been recognized and this make targeted molecular testing for single genes less favorable, instead there is a gaining interest for multi-gene panel-based approaches detecting both SNVs, indels and CNVs in the same assay. We applied a panel including 19 CRC susceptibility genes to 91 individuals of six phenotypic subgroups. Targeted NGS-based sequencing of the whole gene regions including introns of the 19 genes was used. The individuals had a family history of CRC or had a phenotype consistent with a known CRC syndrome. The purpose of the study was to demonstrate the diagnostic difficulties linked to genotype-phenotype diversity and the benefits of using a gene panel. Pathogenicity classification was carried out on 46 detected variants. In total we detected sixteen pathogenic or likely pathogenic variants and 30 variants of unknown clinical significance. Four of the pathogenic or likely pathogenic variants were found in BMPR1A in patients with unexplained familial adenomatous polyposis or atypical adenomatous polyposis, which extends the genotype-phenotype spectrum for this gene. Nine patients had more than one variant remaining after the filtration, including three with truncating mutations in BMPR1A, PMS2 and AXIN2. CNVs were found in three patients, in upstream regions of SMAD4, MSH3 and CTNNB1, and one additional individual harbored a 24.2 kb duplication in CDH1 intron1.Electronic supplementary materialThe online version of this article (doi:10.1007/s10689-016-9934-0) contains supplementary material, which is available to authorized users.
Hereditary factors are thought to play a role in at least one third of patients with colorectal cancer (CRC) but only a limited proportion of these have mutations in known high‐penetrant genes. In a relatively large part of patients with a few or multiple colorectal polyps the underlying genetic cause of the disease is still unknown. Using exome sequencing in combination with linkage analyses together with detection of copy‐number variations (CNV), we have identified a duplication in the regulatory region of the GREM1 gene in a family with an attenuated/atypical polyposis syndrome. In addition, 107 patients with colorectal cancer and/or polyposis were analyzed for mutations in the candidate genes identified. We also performed screening of the exonuclease domain of the POLE gene in a subset of these patients. The duplication of 16 kb in the regulatory region of GREM1 was found to be disease‐causing in the family. Functional analyses revealed a higher expression of the GREM1 gene in colorectal tissue in duplication carriers. Screening of the exonuclease domain of POLE in additional CRC patients identified a probable causative novel variant c.1274A>G, p.Lys425Arg. In conclusion a high penetrant duplication in the regulatory region of GREM1, predisposing to CRC, was identified in a family with attenuated/atypical polyposis. A POLE variant was identified in a patient with early onset CRC and a microsatellite stable (MSS) tumor. Mutations leading to increased expression of genes can constitute disease‐causing mutations in hereditary CRC syndromes. © 2015 The Authors. Genes, Chromosomes & Cancer Published by Wiley Periodicals, Inc.
Background Processed pseudogenes (PΨgs) are disabled gene copies that are transcribed and may affect expression of paralogous genes. Moreover, their insertion in the genome can disrupt the structure or the regulatory region of a gene, affecting its expression level. These events have been identified as occurring mutations during cancer development, thus being able to identify PΨgs and their location will improve their impact on diagnostic testing, not only in cancer but also in inherited disorders. Results We have implemented PΨFinder (P-psy-finder), a tool that identifies PΨgs, annotates known ones and predicts their insertion site(s) in the genome. The tool screens alignment files and provides user-friendly summary reports and visualizations. To demonstrate its applicability, we scanned 218 DNA samples from patients screened for hereditary colorectal cancer. We detected 423 PΨgs distributed in 96% of the samples, comprising 7 different parent genes. Among these, we confirmed the well-known insertion site of the SMAD4-PΨg within the last intron of the SCAI gene in one sample. While for the ubiquitous CBX3-PΨg, present in 82.6% of the samples, we found it reversed inserted in the second intron of the C15ORF57 gene. Conclusions PΨFinder is a tool that can automatically identify novel PΨgs from DNA sequencing data and determine their location in the genome with high sensitivity (95.92%). It generates high quality figures and tables that facilitate the interpretation of the results and can guide the experimental validation. PΨFinder is a complementary analysis to any mutational screening in the identification of disease-causing mutations within cancer and other diseases.
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