Genetics Program, Instituto Nacional de Câncer, Rio de Janeiro, Brazil; Genetics Department, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Genetics Program, Instituto Nacional de Câncer, Rio de Janeiro, Brazil; Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany.
Exp Eye Res. 2022 Nov;224:109211. doi: 10.1016/j.exer.2022.109211. Epub 2022 Aug 17.
Retinoblastoma is a rare childhood tumor caused by the inactivation of both copies of the RB1 gene. Early diagnosis and identification of heritable RB1 mutation carriers can improve the disease outcome and management via genetic counseling. We used the Multiplex Ligation-dependent Probe Amplification (MLPA) method to analyze the RB1 gene and flanking regions in blood samples from 159 retinoblastoma patients previously negative for RB1 point mutations via Sanger sequencing. We detected a wide spectrum of germline chromosomal alterations, ranging from partial loss or duplication of RB1 to large deletions spanning RB1 and adjacent genes. Mutations were validated via karyotyping, fluorescent in situ hybridization (FISH), SNP-arrays (Single Nucleotide Polymorphism-arrays) and/or quantitative relative real-time PCR. Patients with leukocoria as a presenting symptom showed reduced death rate (p = 0.013) and this sign occurred more frequently among carriers of two breakpoints within RB1 (p = 0.05). All unilateral cases presented both breakpoints outside of RB1 (p = 0.0075). Patients with one breakpoint within RB1 were diagnosed at earlier ages (p = 0.017). Our findings characterize the mutational spectrum of a Brazilian cohort of retinoblastoma patients and point to a possible relationship between the mutation breakpoint location and tumor outcome, contributing to a better prospect of the genotype/phenotype correlation and adding to the wide diversity of germline mutations involving RB1 and adjacent regions in retinoblastoma.
视网膜母细胞瘤是一种罕见的儿童肿瘤，由 RB1 基因的两个拷贝失活引起。早期诊断和识别遗传性 RB1 突变携带者可以通过遗传咨询改善疾病结局和管理。我们使用多重连接依赖性探针扩增 (MLPA) 方法分析了 159 例先前通过 Sanger 测序未发现 RB1 点突变的视网膜母细胞瘤患者的血液样本中的 RB1 基因和侧翼区域。我们检测到了广泛的种系染色体改变，从 RB1 的部分缺失或重复到跨越 RB1 和相邻基因的大片段缺失。通过核型分析、荧光原位杂交 (FISH)、SNP 芯片 (单核苷酸多态性芯片) 和/或定量相对实时 PCR 验证了突变。以白瞳为首发症状的患者死亡率降低 (p=0.013)，并且 RB1 内有两个断点的携带者中更常出现这种症状 (p=0.05)。所有单侧病例均显示 RB1 以外的两个断点 (p=0.0075)。有一个断点在 RB1 内的患者被诊断的年龄更早 (p=0.017)。我们的发现描述了巴西视网膜母细胞瘤患者队列的突变谱，并指出突变断点位置与肿瘤结局之间可能存在关系，有助于更好地预测基因型/表型相关性，并增加涉及 RB1 和视网膜母细胞瘤中相邻区域的种系突变的广泛多样性。
