Advantages of next-generation sequencing in revealing low-level somatic mosaicism in blood samples of retinoblastoma patients

Abstract

Background: Retinoblastoma (RB) is an embryonic malignant tumor of retina caused by inactivation of both alleles of the RB1 tumor suppressor gene. Identifying low-level mosaic mutations in RB1 gene in blood samples is challenging. Mosaic mutations arise in early embryogenesis and require high-resolution techniques for detection. In approximately 10% of families, the initial RB1 mutation is mosaic. The ability to identify RB1 mosaicism is important for genetic counseling because mosaicism increases the risk for developing RB in the other eye, second cancers and transmitting the mutation to progeny. Method(s): Using NGS we have evaluated the spectrum and frequency of RB1 mutations mosaicism in peripheral blood of 120 patients with sporadic RB (82 unilateral and 38 bilateral). Result(s): In 5,8% (7/120) of patients a low-level mosaic mutation was found. The spectrum of identified mosaic RB1 mutations, the degree of mosaicism and clinical characteristics are shown in the table. Additionally, we analyzed the Sanger sequencing data from 72 blood samples from patients with sporadic RB (48 unilateral and 24 bilateral), performed earlier in our laboratory, and have not identified mosaic cases. 404P Advantages of next-generation sequencing in revealing low-level somatic mosaicism in blood samples of retinoblastoma patients E.A. Alekseeva1, V.M. Kozlova2, T.L. Ushakova2, A.S. Tanas1, O.V. Babenko1, T.P. Kazubskaya2, V.V. Strelnikov1, D.V. Zaletaev3 1Laboratory of Epigenetics, Research Centre for Medical Genetics, Moscow, Russian Federation, 2Institute of Pediatric Oncology, N. N. Blokhin Science Medical Research Center of Oncology, Moscow, Russian Federation, 3Laboratory of Medical Genetics, Sechenov First Moscow State Medical University, Moscow, Russian Federation Background: Retinoblastoma (RB) is an embryonic malignant tumor of retina caused by inactivation of both alleles of the RB1 tumor suppressor gene. Identifying low-level mosaic mutations in RB1 gene in blood samples is challenging. Mosaic mutations arise in early embryogenesis and require high-resolution techniques for detection. In approximately 10% of families, the initial RB1 mutation is mosaic. The ability to identify RB1 mosaicism is important for genetic counseling because mosaicism increases the risk for developing RB in the other eye, second cancers and transmitting the mutation to progeny. Method(s): Using NGS we have evaluated the spectrum and frequency of RB1 mutations mosaicism in peripheral blood of 120 patients with sporadic RB (82 unilateral and 38 bilateral). Result(s): In 5,8% (7/120) of patients a low-level mosaic mutation was found. The spectrum of identified mosaic RB1 mutations, the degree of mosaicism and clinical characteristics are shown in the table. Additionally, we analyzed the Sanger sequencing data from 72 blood samples from patients with sporadic RB (48 unilateral and 24 bilateral), performed earlier in our laboratory, and have not identified mosaic cases. (Table Presented).