A novel mutation (I143NT) in guanylate cyclase-activating protein 1 (GCAP1) associated with autosomal dominant cone degeneration
A novel mutation (I143NT) in guanylate cyclase-activating protein 1 (GCAP1) associated with autosomal dominant cone degeneration
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DOI：
10.1167/iovs.04-0590
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发表时间：
2004-11-01
影响因子：
4.4
通讯作者：
Baehr, W
中科院分区：
文献类型：
--
作者：
Nishiguchi, KM;Sokal, I;Baehr, W
目的。鉴定鸟苷酸环化酶激活蛋白 1 (GCAP1) 和 GCAP2 基因的致病性突变，并表征突变对鸟苷酸环化酶 (GC) 刺激的生化影响。方法。通过直接测序，分别对 216 名患有各种遗传性视网膜疾病的患者和 421 名患者进行了 GCAP1 和 GCAP2 基因突变筛查。通过使用重组蛋白、免疫印迹、GC 的 Ca2+ 依赖性刺激、荧光发射光谱以及在不存在和存在 Ca2+ 的情况下限制 21 蛋白水解，进一步对与常染色体显性锥体变性分离的 GCAP1 突变进行生化评估。结果。在患有常染色体显性锥体变性的杂合子父子中发现了一种新的 GCAP1 突变 I143NT（密码子 143 处的 Ile 被 ASH 和 Thr 取代），影响 EF4 Ca2+ 结合环。与视杆细胞功能相比，两名患者的视锥细胞功能损失要大得多。先前在尸检时对父亲（75 岁）眼睛进行的组织病理学评估显示，没有中心凹视锥细胞，但在周边视网膜中残留有一些分散的视锥细胞。生化分析表明，GCAP1-I143NT 突变体采用了易于蛋白水解的构象，并且该突变体在高 Ca2+ 浓度下仅部分抑制 GC。患有非典型或隐性视网膜色素变性 (RP) 的个体患者具有致病性未知的额外杂合 GCAP1-T114I 和 GCAP2 基因变化（V85M 和 F150C）。结论。一种新的 GCAP1 突变 I143NT 会引起一种常染色体显性视锥细胞变性，这种变性会在中年时破坏中心凹视锥细胞，但在长达 75 岁的时间内，周边视网膜中的一些视锥细胞仍保留下来。 GCAP1-I143NT 突变蛋白的特性表明，高 Ca2+ 浓度不会使其完全失活，而暗适应过程中应该会发生这种情况。突变体 GCAP1 的持续活性可能导致暗视 cGMP 水平高于正常水平，这反过来又可能导致视锥细胞逐渐丧失。
PURPOSE. To identify pathogenic mutations in the guanylate cyclase-activating protein 1 (GCAP1) and GCAP2 genes and to characterize the biochemical effect of mutation on guanylate cyclase (GC) stimulation.METHODS. The GCAP1 and GCAP2 genes were screened by direct sequencing for mutations in 216 patients and 421 patients, respectively, with various hereditary retinal diseases. A mutation in GCAP1 segregating with autosomal dominant cone degeneration was further evaluated biochemically by employing recombinant proteins, immunoblotting, Ca2+-dependent stimulation of GC, fluorescence emission spectra, and limited 21 proteolysis in the absence and presence of Ca2+.RESULTS. A novel GCAP1 mutation, I143NT (substitution of Ile at codon 143 by ASH and Thr), affecting the EF4 Ca2+-binding loop, was identified in a heterozygote father and son with autosomal dominant cone degeneration. Both patients had much greater loss of cone function versus rod function; previous histopathologic evaluation of the father's eyes at autopsy (age 75 years) showed no foveal cones but a few, scattered cones remaining in the peripheral retina. Biochemical analysis showed that the GCAP1-I143NT mutant adopted a conformation susceptible to proteolysis, and the mutant inhibited GC only partially at high Ca2+ concentrations. Individual patients with atypical or recessive retinitis pigmentosa (RP) had additional heterozygous GCAP1-T114I and GCAP2 gene changes (V85M and F150C) of unknown pathogenicity.CONCLUSIONS. A novel GCAP1 mutation, I143NT, caused a form of autosomal dominant cone degeneration that destroys foveal cones by mid-life but spares some cones in the peripheral retina up to 75 years. Properties of the GCAP1-I143NT mutant protein suggested that it is incompletely inactivated by high Ca2+ concentrations as should occur with dark adaptation. The continued activity of the mutant GCAP1 likely results in higher-than-normal scotopic cGMP levels which may, in turn, account for the progressive loss of cones.