TY - JOUR
T1 - High-sensitivity sequencing reveals multi-organ somatic mosaicism causing DICER1 syndrome
AU - de Kock, Leanne
AU - Wang, Yu Chang
AU - Revil, Timothée
AU - Badescu, Dunarel
AU - Rivera, Barbara
AU - Sabbaghian, Nelly
AU - Wu, Mona
AU - Weber, Evan
AU - Sandoval, Claudio
AU - Hopman, Saskia M J
AU - Merks, Johannes H M
AU - van Hagen, Johanna M
AU - Bouts, Antonia H M
AU - Plager, David A
AU - Ramasubramanian, Aparna
AU - Forsmark, Linus
AU - Doyle, Kristine L
AU - Toler, Tonja
AU - Callahan, Janine
AU - Engelenberg, Charlotte
AU - Bouron-Dal Soglio, Dorothée
AU - Priest, John R
AU - Ragoussis, Jiannis
AU - Foulkes, William D
N1 - 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/
PY - 2015/10
Y1 - 2015/10
N2 - 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.METHODS AND 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.
AB - 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.METHODS AND 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.
KW - Child
KW - Child, Preschool
KW - Computational Biology/methods
KW - DEAD-box RNA Helicases/genetics
KW - DNA Mutational Analysis
KW - Female
KW - Genetic Association Studies
KW - High-Throughput Nucleotide Sequencing/methods
KW - Humans
KW - Loss of Heterozygosity
KW - Male
KW - Mosaicism
KW - Mutation
KW - Neoplasms, Multiple Primary/diagnosis
KW - Phenotype
KW - Ribonuclease III/genetics
KW - Sensitivity and Specificity
KW - Syndrome
U2 - 10.1136/jmedgenet-2015-103428
DO - 10.1136/jmedgenet-2015-103428
M3 - Article
C2 - 26475046
SN - 0022-2593
VL - 53
SP - 43
EP - 52
JO - Journal of medical genetics
JF - Journal of medical genetics
IS - 1
ER -