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Abstract：
Best vitelliform macular dystrophy (BD), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and the autosomal recessive bestrophinopathy (ARB), together known as the bestrophinopathies, are caused by mutations in the bestrophin-1 (BEST1) gene affecting anion transport through the plasma membrane of the retinal pigment epithelium (RPE). To date, while no treatment exists a better understanding of BEST1-related pathogenesis may help to define therapeutic targets. Here, we systematically characterize functional consequences of mutant BEST1 in thirteen RPE patient cell lines differentiated from human induced pluripotent stem cells (hiPSCs). Both BD and ARB hiPSC-RPEs display a strong reduction of BEST1-mediated anion transport function compared to control, while ADVIRC mutations trigger an increased anion permeability suggesting a stabilized open state condition of channel gating. Furthermore, BD and ARB hiPSC-RPEs differ by the degree of mutant protein turnover and by the site of subcellular protein quality control with adverse effects on lysosomal pH only in the BD-related cell lines. The latter finding is consistent with an altered processing of catalytic enzymes in the lysosomes. The present study provides a deeper insight into distinct molecular mechanisms of the three bestrophinopathies facilitating functional categorization of the more than 300 known BEST1 mutations that result into the distinct retinal phenotypes.
摘要：
最佳卵黄样黄斑营养不良（BD），常染色体显性遗传性玻璃体视网膜脉络膜样病变（ADVIRC），和常染色体隐性遗传的bestrophinopathy（ARB），一起被称为诱发素病，是由bestrophin-1（BEST1）基因突变引起的，该基因突变影响了阴离子通过视网膜色素上皮（RPE）质膜的转运。迄今为止,虽然没有治疗方法，但更好地理解BEST1相关的发病机制可能有助于确定治疗靶点。这里,我们系统地描述了从人诱导多能干细胞（hiPSCs）分化的13种RPE患者细胞系中突变BEST1的功能后果。与对照相比，BD和ARBhiPSC-RPE均表现出BEST1介导的阴离子转运功能的强烈降低，而ADVIRC突变引发阴离子通透性增加，表明通道门控的开放状态稳定。此外，BD和ARBhiPSC-RPE的差异在于突变蛋白周转的程度和亚细胞蛋白质量控制的位点，仅在BD相关细胞系中对溶酶体pH产生不利影响。后一发现与溶酶体中催化酶的加工改变相一致。本研究提供了更深入的见解，以促进300多个已知BEST1突变导致不同的视网膜表型的功能分类的三种bestrophines病的不同分子机制。
