中国与日本视网膜细胞瘤患者RB1基因突变特性分析

The characteristics of RB1 gene mutation in Chinese and Japanese patients with retinoblastoma

目的：比较中国与日本视网膜母细胞瘤(retinoblastoma,RB)患者RB1基因突变发生的位点，了解其RB1基因突变的特点。方法：应用PCR-SSCP/异源双链法筛查新收集RB患者的白细胞基因组DNA，测序分析确定突变。结合以前的工作，分析中国与日本RB患者RB1基因突变发生的特性。结果：在新收集的RB患者中，确定4例RB1基因生殖细胞性突变：G→T(GGA→TGA)/Gly86stop;delTT(ACTTGG→ACGG)/CODON76～77;C→T(CAT→TAT)/His129Tyr;TT→A(ATTCCT→ATACT)/codon369～370。结合以前的报道，我们共确定了21个突变，散发11个外显子及3个内含子。85%突变形成截断蛋白，95%突变影响RB蛋白(pRB)大袋立体结构。点突变所占比例最高(52%)；复杂突变所占比例虽然只有10%，但比国外报道的比例(2%)高出许多。结论：中国与日本RB患者RB1基因突变以微小突变为主，散发在多个不同的外显子，绝大部分严重影响pRB的正常功能。突变方式有所侧重，复杂突变的比例相对较高，存在一定的种族特异性。

Objective： To explore the characteristics of the RB1 gene mutation in Chinese and Japanese patients with retinoblastoma based upon exon by exon screening. Methods： Newly collected leukocyte DNA from retinoblastoma patients was analyzed by using PCR SSCP/heteroduplex method. The mutation was identified by cloning and sequencing. The spectrum of RB1 gene mutation was analyzed based on this study and our previous reports. Results： Four new germline mutations in the RB1 gene were identified in newly collected genomic DNA from RB patients： G→ T(GGA→ TGA)/Gly86stop； del TT(ACTTGG→ ACGG)/codon76～ 77； C→ T(CAT→ TAT)/ His129Tyr； TT→ A(ATTCCT→ ATACT)/codon369～ 370. Together with our previous work, there are 21 germline mutations identified in the RB1 gene in Chinese and Japanese RB patients, which spread in 11 exons and 3 introns. Most of mutations (85％ ) created a premature truncated RB protein (pRB). About 95％ of the mutations disrupted the large pocket domain of the pRB. The ratio of point mutation was the commonest (52％ ). Although complex mutation was only found in 10％ of the patients, but it was higher than that in the other report (2％ ). Conclusion： Mutations in RB1 gene involving a few base pairs are common in Chinese and Japanese patients with retinoblastoma. Such mutation may spread in every exon of the RB1 gene and usually disrupts the normal function of pRB. Complex mutation uppears more common in Asian than in Caucasian.