Payne A, Vithana E, Khaliq S, Hameed A, Deller J, Abu-Safieh L, Kermani S, Leroy B P, Mehdi S Q, Moore A T, Bird A C, Bhattacharya S S
Department of Molecular Genetics, Institute of Ophthalmology, Moorfields Eye Hospital, London, United Kingdom.
Invest Ophthalmol Vis Sci. 2000 Dec;41(13):4069-73.
Recent reports have shown that the autosomal dominant retinitis pigmentosa (adRP) phenotype linked to the pericentric region of chromosome 8 is associated with mutations in a gene designated RP1. Screening of the whole gene in a large cohort of patients has not been undertaken to date. To assess the involvement and character of RP1 mutations in adRP, the gene was screened in a panel of 266 unrelated patients of British origin and a Pakistani family linked to this locus.
Patients exhibiting the adRP phenotype were screened for mutations in the four exons of the RP1 gene by heteroduplex analysis and direct sequencing. Linkage of the Pakistani family was achieved using microsatellite markers. Polymerase chain reaction (PCR) products were separated by nondenaturing polyacrylamide gel electrophoresis. Alleles were assigned to individuals, which allowed calculation of LOD scores. Microsatellite marker haplotyping was used to determine ancestry of patients carrying the same mutation.
In the 266 British patients and 1 Pakistani family analyzed, 21 loss-of-function mutations and 7 amino acid substitutions were identified, some of which may also be disease-causing. The mutations, many of which were deletion or insertion events, were clustered in the 5' end of exon 4. Most mutations resulted in a premature termination codon in the mRNA. Haplotype analysis of nine patients carrying an R677X mutation suggested that these patients are not ancestrally related.
RP1 mutations account for 8% to 10% of the mutations in our cohort of British patients. The most common disease-causing mechanism is deduced to be one involving the presence of a truncated protein. Mutations in RP1 have now been described in adRP patients of four ethnically diverse populations. The different disease haplotype seen in the nine patients carrying the same mutation suggests that this mutation has arisen independently many times, possibly due to a mutation hot spot in this part of the gene.
最近的报告显示，与8号染色体着丝粒周围区域相关的常染色体显性视网膜色素变性（adRP）表型与一个名为RP1的基因突变有关。迄今为止，尚未对大量患者群体进行该基因的全基因筛查。为了评估RP1突变在adRP中的参与情况和特征，我们在一组266名英国血统的无关患者以及一个与该基因座相关的巴基斯坦家族中对该基因进行了筛查。
通过异源双链分析和直接测序，对表现出adRP表型的患者进行RP1基因四个外显子的突变筛查。使用微卫星标记实现了对巴基斯坦家族的连锁分析。聚合酶链反应（PCR）产物通过非变性聚丙烯酰胺凝胶电泳进行分离。将等位基因分配给个体，从而可以计算LOD分数。微卫星标记单倍型分析用于确定携带相同突变的患者的祖先。
在分析的266名英国患者和1个巴基斯坦家族中，鉴定出21个功能丧失突变和7个氨基酸替换，其中一些也可能是致病的。这些突变大多是缺失或插入事件，集中在外显子4的5'端。大多数突变导致mRNA中出现提前终止密码子。对9名携带R677X突变的患者进行的单倍型分析表明，这些患者在祖先上没有关联。
在我们的英国患者队列中，RP1突变占突变的8%至10%。最常见的致病机制被推断为涉及截短蛋白的存在。现在已经在四个不同种族群体的adRP患者中描述了RP1突变。在9名携带相同突变的患者中看到的不同疾病单倍型表明，这种突变已经多次独立出现，可能是由于该基因这部分的突变热点。
