RHO基因突变在视网膜色素变性中的分子遗传学分析

Molecular study on rhodopsin gene point mutations in retinitis pigmentosa

目的 探明我国RP患者视紫红质 (rhodopsin ,RHO)基因突变的特征和意义。方法 在 98例RP患者中运用构象敏感凝胶电泳 (conformationsensitivegelelectrophoresis ,CSGE)和DNA直接测序方法检测RHO基因全编码区范围内的点突变。结果 一个ADRP家系的 4名患者第 347密码子发生点突变 ,Pro347Leu ;另一个ADRP家系中一名晚发型患者及其目前还未出现症状的女儿在第 32 7密码子出现点突变 ,Pro32 7( 1 bpdel) ,而对照组 10 0例健康成年人未发现上述两种突变。此外在 1名患者和 2名对照者中还检出一非致病的点突变 ,Ala2 99Ser ,属单个碱基多态现象 (singlenucleotidepolymophism ,SNP)。结论 98例RP先证者中检出 2例携带RHO基因突变 ,由此可初步预测RHO基因在我国RP患者中的突变频率约为 2 % ( 95 %的可信区间为 0 .2 %～ 7.0 % )。Pro347Leu突变改变了视蛋白C末端一段高度保守的氨基酸序列 ,致使该蛋白在胞内的运输发生障碍。Pro32 7( 1 bpdel)使突变蛋白的羧基末端失去了原有的磷酸化位点及上述一段高度保守的功能区 。

Objective To evaluate the patterns and significance of rhodopsin(RHO) gene mutations in Chinese patients with retinitis pigmentosa (RP). Methods Conformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing were employed to detect point mutations occurring in the 5 coding exons and splice sites of rhodopsin gene in 98 subjected patients with RP. Results Four patients of one autosomal dominant RP (ADRP) family were found to have a missense mutation at codon 347, Pro347Leu. One late onset RP patient and her daughter, who had no clinical expressions at present, were discovered to have a novel frameshift mutation at codon 327, Pro327 with only one base loss. None of the 2 mutations was found in 100 normal controls. Ala299Ser was found in one patient as missense mutation. Two control subjects also had Ala299Ser, suggesting its nonpathogenicity and just single nucleotide polymophism (SNP). Conclusion Since 2 out of 98 RP patients have rhodopsin mutations, the frequency of RHO mutations in RP might be about 2.0% (95% confidence interval 0.2%～7.0%). A highly conserved C terminal sequence QVS(A)PA is altered due to Pro347Leu and thereby rhodopsin is misdirected to an incorrect subcellular location. Loss of all phosphorylation sites at the C terminus and the highly conserved sequence QVS(A)PA may occur because of Pro327. To elucidate the predominant biochemical defects in such mutant, the study of transgenic mice and transfected culture cells carrying Pro327(1 bp del) is of great value.