title: High-sensitivity sequencing reveals multi-organ somatic mosaicism causing DICER1 syndrome.
abstract: BACKGROUND
  Somatic mosaicism is being increasingly recognised as an important cause of non-Mendelian presentations of hereditary syndromes. A previous whole-exome sequencing study using DNA derived from peripheral blood identified mosaic mutations in DICER1 in two children with overgrowth and developmental delay as well as more typical phenotypes of germline DICER1 mutation. However, very-low-frequency mosaicism is difficult to detect, and thus, causal mutations can go unnoticed. Highly sensitive, cost-effective approaches are needed to molecularly diagnose these persons. We studied four children with multiple primary tumours known to be associated with the DICER1 syndrome, but in whom germline DICER1 mutations were not detected by conventional mutation detection techniques.
  
  
  RESULTS
  We observed the same missense mutation within the DICER1 RNase IIIb domain in multiple tumours from different sites in each patient, raising suspicion of somatic mosaicism. We implemented three different targeted-capture technologies, including the novel HaloPlex(HS) (Agilent Technologies), followed by deep sequencing, and confirmed that the identified mutations are mosaic in origin in three patients, detectable in 0.24-31% of sequencing reads in constitutional DNA. The mosaic origin of patient 4's mutation remains to be unequivocally established. We also discovered likely pathogenic second somatic mutations or loss of heterozygosity (LOH) in tumours from all four patients.
  
  
  CONCLUSIONS
  Mosaic DICER1 mutations are an important cause of the DICER1 syndrome in patients with severe phenotypes and often appear to be accompanied by second somatic truncating mutations or LOH in the associated tumours. Furthermore, the molecular barcode-containing HaloPlex(HS) provides the sensitivity required for detection of such low-level mosaic mutations and could have general applicability.
authors.affiliation: Department of Human Genetics, McGill University, Montréal, Québec, Canada Lady Davis Institute, Segal Cancer Centre, Jewish General Hospital, Montréal, Québec, Canada.
authors.forename: Leanne
authors.initials: L
authors.lastname: de Kock
authors.affiliation: Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, McGill University, Montréal, Québec, Canada.
authors.forename: Yu Chang
authors.initials: YC
authors.lastname: Wang
authors.affiliation: Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, McGill University, Montréal, Québec, Canada.
authors.forename: Timothée
authors.initials: T
authors.lastname: Revil
authors.affiliation: Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, McGill University, Montréal, Québec, Canada.
authors.forename: Dunarel
authors.initials: D
authors.lastname: Badescu
authors.affiliation: Department of Human Genetics, McGill University, Montréal, Québec, Canada Lady Davis Institute, Segal Cancer Centre, Jewish General Hospital, Montréal, Québec, Canada.
authors.forename: Barbara
authors.initials: B
authors.lastname: Rivera
authors.affiliation: Lady Davis Institute, Segal Cancer Centre, Jewish General Hospital, Montréal, Québec, Canada.
authors.forename: Nelly
authors.initials: N
authors.lastname: Sabbaghian
authors.affiliation: Department of Human Genetics, McGill University, Montréal, Québec, Canada Lady Davis Institute, Segal Cancer Centre, Jewish General Hospital, Montréal, Québec, Canada.
authors.forename: Mona
authors.initials: M
authors.lastname: Wu
authors.affiliation: Department of Medical Genetics, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
authors.forename: Evan
authors.initials: E
authors.lastname: Weber
authors.affiliation: Department of Pediatrics, New York Medical College and Maria Fareri Children's Hospital, Valhalla, New York, USA.
authors.forename: Claudio
authors.initials: C
authors.lastname: Sandoval
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital, Academic Medical Center, Amsterdam Zuidoost, The Netherlands.
authors.forename: Saskia M J
authors.initials: SM
authors.lastname: Hopman
authors.affiliation: Department of Pediatric Oncology, Emma Children's Hospital, Academic Medical Center, Amsterdam Zuidoost, The Netherlands.
authors.forename: Johannes H M
authors.initials: JH
authors.lastname: Merks
authors.affiliation: Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Johanna M
authors.initials: JM
authors.lastname: van Hagen
authors.affiliation: Department of Pediatric Nephrology, Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Antonia H M
authors.initials: AH
authors.lastname: Bouts
authors.affiliation: Glick Eye Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Plager
authors.affiliation: Glick Eye Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA Department of Ophthalmology, University of Louisville, Kentucky, USA.
authors.forename: Aparna
authors.initials: A
authors.lastname: Ramasubramanian
authors.affiliation: Agilent Technologies, Santa Clara, California, USA.
authors.forename: Linus
authors.initials: L
authors.lastname: Forsmark
authors.affiliation: North Hills, California, USA.
authors.forename: Kristine L
authors.initials: KL
authors.lastname: Doyle
authors.affiliation: Petersburg, Indiana, USA.
authors.forename: Tonja
authors.initials: T
authors.lastname: Toler
authors.affiliation: Mahopac, New York, USA.
authors.forename: Janine
authors.initials: J
authors.lastname: Callahan
authors.affiliation: Amsterdam, The Netherlands.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Engelenberg
authors.affiliation: Department of Pathology, CHU-Sainte Justine and University of Montreal, Montréal, Québec, Canada.
authors.forename: Dorothée
authors.initials: D
authors.lastname: Bouron-Dal Soglio
authors.affiliation: Minneapolis, Minnesota, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Priest
authors.affiliation: Department of Human Genetics, McGill University and Genome Quebec Innovation Centre, McGill University, Montréal, Québec, Canada.
authors.forename: Jiannis
authors.initials: J
authors.lastname: Ragoussis
authors.affiliation: Department of Human Genetics, McGill University, Montréal, Québec, Canada Lady Davis Institute, Segal Cancer Centre, Jewish General Hospital, Montréal, Québec, Canada Department of Medical Genetics, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada Program in Cancer Genetics, Department of Oncology and Human Genetics, McGill University, Montréal, Québec, Canada.
authors.forename: William D
authors.initials: WD
authors.lastname: Foulkes
mesh_terms: D002648:Child; D002675:Child, Preschool; D019295:Computational Biology / Q000379:methods; D053487:DEAD-box RNA Helicases / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D056726:Genetic Association Studies; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods* / Q000592:standards; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D009030:Mosaicism; D009154:Mutation; D009378:Neoplasms, Multiple Primary / Q000175:diagnosis / Q000235:genetics*; D010641:Phenotype; D043244:Ribonuclease III / Q000235:genetics*; D012680:Sensitivity and Specificity; D013577:Syndrome
chemical_list: C408087:DICER1 protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases
keywords: Genetics; Molecular genetics; Paediatric oncology