视网膜色素变性患者的相关致病基因PDE6B突变及其临床表型分析

A study of PDE6B gene mutation and phenotype in Chinese cases with retinitis pigmentosa

目的 了解磷酸二酯酶 β亚单位 (phosphodiesteraseβsubunit,PDE6B)基因突变在我国视网膜色素变性 (retinitispigmentosa ,RP)患者中的突变形式及其临床表型特征。方法 应用聚合酶链反应 异源双链 单链构像多态性及DNA序列分析技术 ,对收集的 35个常染色体隐性家系和 5 5例散发RP患者进行PDE6B基因的 2 2个外显子和 5′ 端非编码区 ( 5′ UTR)全基因扫描 ,并行眼部检查及家系分析。结果 检测出 1例散发性RP患者第 6外显子第 2 492位点T→C碱基突变导致其编码氨基酸由甘氨酸变为丝氨酸 ,第 10外显子 5′ 端上游 (第 9内含子内 )第 2 7与 2 8碱基之间有 2个碱基 (TG)插入突变。以上两种突变在 10 0例正常人中均未检测出。RP患者表现为视乳头萎缩、血管变细及色素散布。多焦视网膜电图检测提示视杆细胞受损较重。 1例常染色体隐性家系患者PDE6B基因第 11外显子 5′ 端上游第 19位碱基 (第 10内含子内 )发生G→A颠换。另 2例散发RP患者分别发现第 4外显子 5′ 端上游 30与 31碱基间 2个碱基 (GT)插入和第 18外显子 3′ 端下游第 15个碱基发生G→C转换。结论 PDE6B基因的复合杂合突变可能是我国散发性RP患者的致病基因 ,通常以视杆细胞受累较重 ,其眼部临床表现符合典型的RP患者特征 。

Objective To identify the mutation spectrum of phosphodiesterase β subunit (PDE6B) gene, the incidence in Chinese patients with retinitis pigmentosa (RP) and their clinical phenotypic characteristics. Methods Screening of mutations within PDE6B gene was performed using polymerase chain reaction-heteroduplex-single strand conformation polymorphism (PCR-SSCP) and DNA sequence in 35 autosomal recessive (AR) RP and 55 sporadic RP cases. The phenotypes of the patients with the gene mutation were examined and analyzed. Results Novel complex heterozygous variants of PDE6B gene in a sporadic case, a T to C transversion in codon 323 resulting in the substitution of Gly by Ser and 2 base pairs (bp: G and T) insert between the 27th-28th bp upstream of the 5′-end of exon 10 were both present in a same isolate RP. But they are not found in 100 unrelated healthy individuals. Ocular findings showed diffuse pigmentary retinal degeneration in the midperipheral and peripheral fundi, optic atrophy and vessel attenuation. Multi-focal ERG indicated that the rod function was more severely deteriorated. A mutation was found in a case with RP in a ARRP family, a G to A transversion at 19th base upstream 5'-end of exon 11 (within intron 10 ) of PDE6B gene. A sporadic RP carried a sequence variant of PDE6B gene, a G to C transition, at the 15th base adjacent to the 3′-end of exon l8. In another isolate case with RP was found 2 bp (GT) insert between 31st and 32nd base upstream 5′-end of exon 4 (in intron 3) of PDE6B gene. Conclusions There are novel complex heterozygous mutations of PDE6B gene responsible for a sporadic RP patient in China. This gene mutation associated with rod deterioration and RP. Several DNA variants were found in introns of PDE6B gene in national population.