Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovakia.
Department of Ophthalmology, Bambino Gesù IRCCS Children's Hospital, Rome, Italy.
J Transl Med. 2019 Oct 1;17(1):330. doi: 10.1186/s12967-019-2080-3.
Best vitelliform macular dystrophy (BVMD) is an autosomal dominant macular degeneration. The typical central yellowish yolk-like lesion usually appears in childhood and gradually worsens. Most cases are caused by variants in the BEST1 gene which encodes bestrophin-1, an integral membrane protein found primarily in the retinal pigment epithelium.
Here we describe the spectrum of BEST1 variants identified in a cohort of 57 Italian patients analyzed by Sanger sequencing. In 13 cases, the study also included segregation analysis in affected and unaffected relatives. We used molecular mechanics to calculate two quantitative parameters related to calcium-activated chloride channel (CaCC composed of 5 BEST1 subunits) stability and calcium-dependent activation and related them to the potential pathogenicity of individual missense variants detected in the probands.
Thirty-six out of 57 probands (63% positivity) and 16 out of 18 relatives proved positive to genetic testing. Family study confirmed the variable penetrance and expressivity of the disease. Six of the 27 genetic variants discovered were novel: p.(Val9Gly), p.(Ser108Arg), p.(Asn179Asp), p.(Trp182Arg), p.(Glu292Gln) and p.(Asn296Lys). All BEST1 variants were assessed in silico for potential pathogenicity. Our computational structural biology approach based on 3D model structure of the CaCC showed that individual amino acid replacements may affect channel shape, stability, activation, gating, selectivity and throughput, and possibly also other features, depending on where the individual mutated amino acid residues are located in the tertiary structure of BEST1. Statistically significant correlations between mean logMAR best-corrected visual acuity (BCVA), age and modulus of computed BEST1 dimerization energies, which reflect variations in the in CaCC stability due to amino acid changes, permitted us to assess the pathogenicity of individual BEST1 variants.
Using this computational approach, we designed a method for estimating BCVA progression in patients with BEST1 variants.
Best 病（Best vitelliform macular dystrophy，BVMD）是一种常染色体显性遗传性黄斑变性。典型的中心性黄色蛋黄样病变通常在儿童期出现，并逐渐恶化。大多数病例是由 BEST1 基因突变引起的，该基因编码主要存在于视网膜色素上皮的完整膜蛋白——贝斯特素-1（bestrophin-1）。
本研究通过桑格测序分析了 57 名意大利患者的 BEST1 变异谱。在 13 例中，研究还包括受累和未受累亲属的分离分析。我们使用分子力学计算了与钙激活氯离子通道（由 5 个 BEST1 亚基组成的 CaCC）稳定性和钙依赖性激活相关的两个定量参数，并将其与在先证者中检测到的个体错义变异的潜在致病性相关联。
57 名先证者中有 36 名（63%阳性率）和 18 名亲属中的 16 名（89%阳性率）基因检测阳性。家系研究证实了该疾病的可变外显率和表现度。发现的 27 种遗传变异中有 6 种是新的：p.(Val9Gly)、p.(Ser108Arg)、p.(Asn179Asp)、p.(Trp182Arg)、p.(Glu292Gln)和 p.(Asn296Lys)。所有的 BEST1 变异均进行了潜在致病性的计算机预测。我们基于 CaCC 三维模型结构的计算结构生物学方法表明，个体氨基酸替换可能会影响通道形状、稳定性、激活、门控、选择性和通透性，并且可能还会影响其他特性，具体取决于个体突变氨基酸残基在 BEST1 三级结构中的位置。平均 logMAR 最佳矫正视力（BCVA）、年龄和计算出的 BEST1 二聚体化能量的模数之间存在显著的相关性，这反映了由于氨基酸变化导致 CaCC 稳定性的变化，使我们能够评估个体 BEST1 变异的致病性。
使用这种计算方法，我们设计了一种用于估计 BEST1 变异患者的 BCVA 进展的方法。
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