title: Next generation sequencing in sporadic retinoblastoma patients reveals somatic mosaicism.
abstract: In about 50% of sporadic cases of retinoblastoma, no constitutive RB1 mutations are detected by conventional methods. However, recent research suggests that, at least in some of these cases, there is somatic mosaicism with respect to RB1 normal and mutant alleles. The increased availability of next generation sequencing improves our ability to detect the exact percentage of patients with mosaicism. Using this technology, we re-tested a series of 40 patients with sporadic retinoblastoma: 10 of them had been previously classified as constitutional heterozygotes, whereas in 30 no RB1 mutations had been found in lymphocytes. In 3 of these 30 patients, we have now identified low-level mosaic variants, varying in frequency between 8 and 24%. In 7 out of the 10 cases previously classified as heterozygous from testing blood cells, we were able to test additional tissues (ocular tissues, urine and/or oral mucosa): in three of them, next generation sequencing has revealed mosaicism. Present results thus confirm that a significant fraction (6/40; 15%) of sporadic retinoblastoma cases are due to postzygotic events and that deep sequencing is an efficient method to unambiguously distinguish mosaics. Re-testing of retinoblastoma patients through next generation sequencing can thus provide new information that may have important implications with respect to genetic counseling and family care.
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Amitrano
authors.affiliation: Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Annabella
authors.initials: A
authors.lastname: Marozza
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Somma
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Imperatore
authors.affiliation: Unit of Ophthalmology, Retinoblastoma Referral Center, Department of Surgery, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Theodora
authors.initials: T
authors.lastname: Hadjistilianou
authors.affiliation: Unit of Ophthalmology, Retinoblastoma Referral Center, Department of Surgery, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: De Francesco
authors.affiliation: Pathology, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Toti
authors.affiliation: Unit of Pediatrics, Department of Maternal, Newborn and Child Health, Azienda Ospedaliera Universitaria Senese, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Galimberti
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Meloni
authors.affiliation: IRCCS MultiMedica, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cetta
authors.affiliation: Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Piu
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Di Marco
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Dosa
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Lo Rizzo
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Carignani
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Mencarelli
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Mari
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.|Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Renieri
authors.affiliation: Medical Genetics, Department of Medical Biotechnologies, University of Siena, Policlinico 'Santa Maria alle Scotte', Siena, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ariani
mesh_terms: D000293:Adolescent; D000328:Adult; D000483:Alleles; D002648:Child; D002675:Child, Preschool; D005260:Female; D018095:Germ-Line Mutation; D006579:Heterozygote; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008297:Male; D009030:Mosaicism; D012175:Retinoblastoma / Q000235:genetics* / Q000503:physiopathology; D016160:Retinoblastoma Protein / Q000235:genetics*
chemical_list: D016160:Retinoblastoma Protein