100例视网膜色素变性患者中视紫红质基因突变的筛选与检测

目的 研究视紫红质（rhodopsin,RHO）基因在中国人视网膜色素变性（retinitis pigmentosa,RP）患者中的突变频率，特征及其在RP发病机理中的作用。方法 运用构象敏感凝胶电泳和DNA直接测序方法对100例香港地区中国RP中层得RHO基因全编码区进行突变的筛选与检测。结果 共发现种碱基变异，其中3种为沉默型突变，两种为错义突变，1种为缺失突变。P347L在1例55岁女性患者及其同样患RP的3名子女 中检出。327（1－bp del）首次在1例53岁的晚发型RP患者中发现。其26岁的女儿同样携带该突变，但目前除眼底色素上皮出现斑点外，还没有RP的任何症状。上述两种突变均未在对照组中发现。结论 100例RP患者中检出两例携带RHO基因突变，由此可预测香港地区约为2．0％（95％的可信区间为0．2％－7．0％）的RP是由RHO基因突变所致。P347L突变改变了RHO基因C末端一段高度保守的氨基酸序列，致使视紫红质蛋白在细胞P内的运输发生障碍。P327（1 bp del）使突变蛋白的羧基末端失去了原有的磷酸化位点及一段高度保守的功能区，其可能的致病机理有待在今后的研究中通过建立相应的转基因模型或细胞培养系统来阐明。

Screening for point mutations in rhodopsin gene among one hundred Chinese patients with retinitis pigmentosa

Objective To test the frequency and pattern of rhodopsin (RHO) mutations in Chinese retinitis pigmentosa (RP) patients and to evaluate their effects in the pathogenesis of RP. Methods Genomic DNA was extracted from peripheral blood samples of 100 Hong Kong Chinese RP patients. Sequence variants of the entire coding exons of the RHO gene were tested using PCR, conformation sensitive gel electrophoresis and DNA sequencing. Results Totally six nucleotide changes were identified, among which three were silent mutations, two missense mutations and one deletion mutation. P347L was found in one RP proband and her three children who also had RP. P327(1 bp del) was novel and detected in a late-onset RP patient of 53 years. Her 26-year-old daughter, also carrying the identified mutation, had no RP phenotypes except for the mottled retinal pigment epithelium (RPE) revealed by fundal examination. Neither of the two mutations was detected in normal controls. Conclusion Two patients had disease-causing mutations in the RHO gene, thus RHO mutations cause about 2.0% (95% confidence interval: 0 2%-7.0%) of all RP among Chinese in Hong Kong. A highly conserved C-terminal sequence QVS(A)PA was altered due to P347L and thereby resulting in an aberrant subcellular localization of rhodopsin. Loss of all six phosphorylatable residues at the C-terminus and the highly conserved C-terminal sequence QVS(A)PA may occur because of P327(1 bp del). To elucidate the predominant biochemical defects in such mutant, transgenic mice and transfected culture cells carrying P327(1 bp del) would be of greatest value.