[Gene diagnosis and genetic counselling of Rb gene mutations in retinoblastoma patients and their family members].

OBJECTIVE

To develop a diagnostic test for direct identification of disease-causing mutation in the patients with retinoblastoma and correct prediction of carrier- status in unaffected adults and newborns in the RB kindred.

METHODS

Southern blot hybridized by Rb cDNA and other intragenic probes were used to detect big deletions or rearrangements at Rb gene locus. SSCP analysis and direct sequencing of primer-directed enzymatic amplification to identify point mutations as small as a single nucleotide change. RFLPs and VNTRs within the Rb gene were used as genetic markers for haplotype analysis.

RESULTS

The probands from 79 RB kindreds were identified to have Rb gene mutation, including 25 somatic mutations and 54 germline mutations (36 new germline mutations, 15 inherited mutations and 3 mosaicisms). The WBC DNAs from their family members were also analyzed for determining origin and carrier of mutation.

CONCLUSION

The direct identification of causing- cancer mutations by combining SSCP analysis and direct DNA sequencing showed many advantages than other indirect methods such as haplotype analysis. It can distinguish hereditary RB from nonhereditary RB and identify the unaffected carriers without family history and informes affected family member. This method is helpful in gene diagnosis and genetic counselling.