Genetic Diagnosis and Counseling of Retinoblastoma
Date Issued
2011
Date
2011
Author(s)
Jan, Shu-Yun
Abstract
Retinoblastoma (RB) is a neoplasm of retinal origin caused by mutations in RB1 gene, the retinoblastoma tumor suppressor gene. To facilitate patient classification and to provide proper genetics counseling, we adopted a multistep molecular screening protocol for detecting RB1 mutations. This protocol included DNA sequencing to identify mutations within coding exons and immediate flanking intronic regions, Multiplex Ligation-dependent Probe Amplification (MLPA) to detect RB1 gene deletions or duplications, MS-MLPA (methylation specific-MLPA) to detect methylation the promoter of RB1 gene. We have collected samples from a total of 63 RB patients. In the 41 patients who have provided peripheral blood, we identified germline RB1 mutations in 16 out of 17 bilateral RB patients (94.1%), and 5 out of 24 unilateral patients (20.8%). In the 22 patients who provided both peripheral blood and tumor tissues, we identified germline RB1 mutations in 5 out of 5 bilateral RB patients (100%), 3 out of 17 unilateral patients, and somatic RB1 mutations in 7 out of 17 unilateral patients (58.8%). In the 22 tumor tissues provided, a total of 13 patients (59.1%) showed loss of heterozygosity (LoH), while only one patient was detected with promotor methylation of RB1 gene (4.5%). We have identified biallelic RB1 gene inactivation, and some conformed with "Two-Hits Hypothesis". In some of the samples, only one of the two RB1 mutations was detected. However, there remained some samples with no mutations detected. Nevertheless, from the MS-MLPA result, the absence of detectable RB1 mutations in the unilateral tumors is presumed to be caused by other genetic mechanisms or genes in the development of RB. Through this genetic diagnosis, we hope to provide the most suitable genetic counseling for Retinoblastoma patients.
Subjects
Retinoblastoma (RB)
Tumor suppressor gene
Loss of heterozygosity (LoH)
Germline mutation
Somatic mutation
Two-Hits Hypothesis
Type
thesis
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