Department of Ophthalmology and Vision Science, University of Arizona, 655 N. Alvernon Way, Suite 108, Tucson, AZ 85711, USA.
Hum Mol Genet. 2010 Mar 15;19(6):1108-18. doi: 10.1093/hmg/ddp583. Epub 2010 Jan 6.
Mutations in BEST1, encoding bestrophin-1 (Best1), cause Best vitelliform macular dystrophy (BVMD), a dominantly inherited macular degeneration characterized by a diminished electrooculogram light peak (LP), lipofuscin in retinal pigment epithelial cells (RPE), and fluid- and debris-filled retinal detachments. To understand the pathogenesis of BVMD we generated knock-in mice carrying the BVMD-causing mutation W93C in Best1. Both Best1(+/W93C)and Best1(W93C/W93C) mice had normal ERG a- and b-waves, but exhibited an altered LP luminance response reminiscent of that observed in BVMD patients. Morphological analysis identified fluid- and debris-filled retinal detachments in mice as young as 6 months of age. By 18-24 months of age Best1(+/W93C)and Best1(W93C/W93C) mice exhibited enhanced accumulation of lipofuscin in the RPE, and a significant deposition of debris composed of unphagocytosed photoreceptor outer segments and lipofuscin granules in the subretinal space. Although Best1 is thought to function as a Ca(2+)-activated Cl(-) channel, RPE cells from Best1(W93C) mice exhibited normal Cl(-) conductances. We have previously shown that Best1(-/-) mice exhibit increased Ca(2+) in response to ATP stimulation. However, ATP-stimulated changes in Ca(2+) in RPE cells from Best1(+/W93C) and Best1(W93C/W93C) mice were suppressed relative to Best1(+/+) littermates. Based on these data we conclude that mice carrying the Best1(W93C) mutation are a valid model for BVMD. Furthermore, these data suggest that BVMD is not because of Best1 deficiency, as the phenotypes of Best1(+/W93C) and Best1(W93C/W93C) mice are distinct from that of Best1(-/-) mice with regard to lipofuscin accumulation, and changes in the LP and ATP Ca(2+) responses.
BEST1 基因突变，编码贝斯特蛋白-1（Bestrophin-1，Best1），导致 Best 型卵黄样黄斑营养不良（Best vitelliform macular dystrophy，BVMD），这是一种常染色体显性遗传性黄斑变性，其特征为视网膜色素上皮细胞（retinal pigment epithelial cells，RPE）中视黄醇脂褐素减少、电生理眼图光峰（light peak，LP）减弱、脂褐素和碎片填充的视网膜脱离。为了了解 BVMD 的发病机制，我们构建了携带 BEST1 基因突变 W93C 的敲入小鼠。Best1(+/W93C) 和 Best1(W93C/W93C) 两种小鼠的视网膜电图 a-和 b-波均正常，但表现出与 BVMD 患者相似的 LP 亮度反应改变。形态学分析发现，6 月龄的小鼠就已经出现脂褐素填充的液体和碎片性视网膜脱离。到 18-24 月龄时，Best1(+/W93C) 和 Best1(W93C/W93C) 小鼠的 RPE 中脂褐素积累明显增加，并且在视网膜下空间有大量未被吞噬的光感受器外节和脂褐素颗粒组成的碎片沉积。尽管 Best1 被认为是一种 Ca(2+)-激活的 Cl(-)通道，但来自 Best1(W93C) 小鼠的 RPE 细胞表现出正常的 Cl(-)电导率。我们之前的研究表明，Best1(-/-) 小鼠在 ATP 刺激下表现出 Ca(2+)的增加。然而，与 Best1(+/+) 同窝仔鼠相比，Best1(+/W93C)和 Best1(W93C/W93C) 小鼠的 RPE 细胞中 ATP 刺激引起的 Ca(2+)变化受到抑制。基于这些数据，我们得出结论，携带 Best1(W93C) 突变的小鼠是 BVMD 的有效模型。此外，这些数据表明，BVMD 不是由于 Best1 缺乏引起的，因为 Best1(+/W93C)和 Best1(W93C/W93C) 小鼠的脂褐素积累、LP 和 ATP Ca(2+) 反应的变化与 Best1(-/-) 小鼠的表型明显不同。
