Isabel Spier1, Dmitriy Drichel2, Martin Kerick3, Jutta Kirfel4, Sukanya Horpaopan5, Andreas Laner6, Stefanie Holzapfel1, Sophia Peters7, Ronja Adam1, Bixiao Zhao8, Tim Becker9, Richard P Lifton8, Sven Perner10, Per Hoffmann11, Glen Kristiansen4, Bernd Timmermann12, Markus M Nöthen13, Elke Holinski-Feder6, Michal R Schweiger3, Stefan Aretz1. 1. Institute of Human Genetics, University of Bonn, Bonn, Germany Center for Hereditary Tumor Syndromes, University of Bonn, Bonn, Germany. 2. German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany. 3. Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany. 4. Center for Hereditary Tumor Syndromes, University of Bonn, Bonn, Germany Institute of Pathology, University of Bonn, Bonn, Germany. 5. Institute of Human Genetics, University of Bonn, Bonn, Germany Department of Anatomy, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand. 6. Medizinische Klinik-Campus Innenstadt, Klinikum der LMU, Munich, Germany MGZ-Center of Medical Genetics, Munich, Germany. 7. Institute of Human Genetics, University of Bonn, Bonn, Germany. 8. Departments of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA. 9. German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany Institute of Medical Biometry, Informatics, and Epidemiology, University of Bonn, Bonn, Germany. 10. Section for Prostate Cancer Research, Institute of Pathology, Center for Integrated Oncology Cologne/Bonn, University Hospital of Bonn, Bonn, Germany. 11. Institute of Human Genetics, University of Bonn, Bonn, Germany Department of Genomics, Life & Brain Center, University of Bonn, Bonn, Germany Division of Medical Genetics, University Hospital Basel and Department of Biomedicine, University of Basel, Basel, Switzerland. 12. Next Generation Sequencing Group, Max Planck Institute for Molecular Genetics, Berlin, Germany. 13. Institute of Human Genetics, University of Bonn, Bonn, Germany Department of Genomics, Life & Brain Center, University of Bonn, Bonn, Germany.
Abstract
BACKGROUND: In 30-50% of patients with colorectal adenomatous polyposis, no germline mutation in the known genes APC, causing familial adenomatous polyposis, MUTYH, causing MUTYH-associated polyposis, or POLE or POLD1, causing polymerase-proofreading-associated polyposis can be identified, although a hereditary aetiology is likely. This study aimed to explore the impact of APC mutational mosaicism in unexplained polyposis. METHODS: To comprehensively screen for somatic low-level APC mosaicism, high-coverage next-generation sequencing of the APC gene was performed using DNA from leucocytes and a total of 53 colorectal tumours from 20 unrelated patients with unexplained sporadic adenomatous polyposis. APC mosaicism was assumed if the same loss-of-function APC mutation was present in ≥ 2 anatomically separated colorectal adenomas/carcinomas per patient. All mutations were validated using diverse methods. RESULTS: In 25% (5/20) of patients, somatic mosaicism of a pathogenic APC mutation was identified as underlying cause of the disease. In 2/5 cases, the mosaic level in leucocyte DNA was slightly below the sensitivity threshold of Sanger sequencing; while in 3/5 cases, the allelic fraction was either very low (0.1-1%) or no mutations were detectable. The majority of mosaic mutations were located outside the somatic mutation cluster region of the gene. CONCLUSIONS: The present data indicate a high prevalence of pathogenic mosaic APC mutations below the detection thresholds of routine diagnostics in adenomatous polyposis, even if high-coverage sequencing of leucocyte DNA alone is taken into account. This has important implications for both routine work-up and strategies to identify new causative genes in this patient group. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/
BACKGROUND: In 30-50% of patients with colorectal adenomatous polyposis, no germline mutation in the known genes APC, causing familial adenomatous polyposis, MUTYH, causing MUTYH-associated polyposis, or POLE or POLD1, causing polymerase-proofreading-associated polyposis can be identified, although a hereditary aetiology is likely. This study aimed to explore the impact of APC mutational mosaicism in unexplained polyposis. METHODS: To comprehensively screen for somatic low-level APC mosaicism, high-coverage next-generation sequencing of the APC gene was performed using DNA from leucocytes and a total of 53 colorectal tumours from 20 unrelated patients with unexplained sporadic adenomatous polyposis. APC mosaicism was assumed if the same loss-of-function APC mutation was present in ≥ 2 anatomically separated colorectal adenomas/carcinomas per patient. All mutations were validated using diverse methods. RESULTS: In 25% (5/20) of patients, somatic mosaicism of a pathogenic APC mutation was identified as underlying cause of the disease. In 2/5 cases, the mosaic level in leucocyte DNA was slightly below the sensitivity threshold of Sanger sequencing; while in 3/5 cases, the allelic fraction was either very low (0.1-1%) or no mutations were detectable. The majority of mosaic mutations were located outside the somatic mutation cluster region of the gene. CONCLUSIONS: The present data indicate a high prevalence of pathogenic mosaic APC mutations below the detection thresholds of routine diagnostics in adenomatous polyposis, even if high-coverage sequencing of leucocyte DNA alone is taken into account. This has important implications for both routine work-up and strategies to identify new causative genes in this patient group. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/
Authors: Anne Ml Jansen; Heleen M van der Klift; Marieke Ae Roos; Jaap Dh van Eendenburg; Carli Mj Tops; Juul T Wijnen; Frederik J Hes; Hans Morreau; Tom van Wezel Journal: Eur J Hum Genet Date: 2018-04-30 Impact factor: 4.246
Authors: Daniel Herzig; Karin Hardiman; Martin Weiser; Nancy You; Ian Paquette; Daniel L Feingold; Scott R Steele Journal: Dis Colon Rectum Date: 2017-09 Impact factor: 4.585
Authors: Ronja Adam; Isabel Spier; Bixiao Zhao; Michael Kloth; Jonathan Marquez; Inga Hinrichsen; Jutta Kirfel; Aylar Tafazzoli; Sukanya Horpaopan; Siegfried Uhlhaas; Dietlinde Stienen; Nicolaus Friedrichs; Janine Altmüller; Andreas Laner; Stefanie Holzapfel; Sophia Peters; Katrin Kayser; Holger Thiele; Elke Holinski-Feder; Giancarlo Marra; Glen Kristiansen; Markus M Nöthen; Reinhard Büttner; Gabriela Möslein; Regina C Betz; Angela Brieger; Richard P Lifton; Stefan Aretz Journal: Am J Hum Genet Date: 2016-07-28 Impact factor: 11.025
Authors: Isabel Spier; Martin Kerick; Dmitriy Drichel; Sukanya Horpaopan; Janine Altmüller; Andreas Laner; Stefanie Holzapfel; Sophia Peters; Ronja Adam; Bixiao Zhao; Tim Becker; Richard P Lifton; Elke Holinski-Feder; Sven Perner; Holger Thiele; Markus M Nöthen; Per Hoffmann; Bernd Timmermann; Michal R Schweiger; Stefan Aretz Journal: Fam Cancer Date: 2016-04 Impact factor: 2.375
Authors: Kevin J Monahan; Nicola Bradshaw; Sunil Dolwani; Bianca Desouza; Malcolm G Dunlop; James E East; Mohammad Ilyas; Asha Kaur; Fiona Lalloo; Andrew Latchford; Matthew D Rutter; Ian Tomlinson; Huw J W Thomas; James Hill Journal: Gut Date: 2019-11-28 Impact factor: 23.059