Center of Ophthalmology, University of Cologne, Cologne, Germany.
PLoS One. 2011;6(8):e22959. doi: 10.1371/journal.pone.0022959. Epub 2011 Aug 2.
Variants in the chromosomal region 10q26 are strongly associated with an increased risk for age-related macular degeneration (AMD). Two potential AMD genes are located in this region: ARMS2 and HTRA1 (high-temperature requirement A1). Previous studies have suggested that polymorphisms in the promotor region of HTRA1 result in overexpression of HTRA1 protein. This study investigated the role of HTRA1 overexpression in the pathogenesis of AMD. Transgenic Htra1 mice overexpressing the murine protein in the retinal pigment epithelium (RPE) layer of the retina were generated and characterized by transmission electron microscopy, immunofluorescence staining and Western Blot analysis. The elastic layer of Bruch's membrane (BM) in the Htra1 transgenic mice was fragmented and less continuous than in wild type (WT) controls. Recombinant HTRA1 lacking the N-terminal domain cleaved various extracellular matrix (ECM) proteins. Subsequent Western Blot analysis revealed an overexpression of fibronectin fragments and a reduction of fibulin 5 and tropoelastin in the RPE/choroid layer in transgenic mice compared to WT. Fibulin 5 is essential for elastogenesis by promoting elastic fiber assembly and maturation. Taken together, our data implicate that HTRA1 overexpression leads to an altered elastogenesis in BM through fibulin 5 cleavage. It highlights the importance of ECM related proteins in the development of AMD and links HTRA1 to other AMD risk genes such as fibulin 5, fibulin 6, ARMS2 and TIMP3.
10q26 染色体区域的变异与年龄相关性黄斑变性 (AMD) 的风险增加密切相关。该区域有两个潜在的 AMD 基因：ARMS2 和 HTRA1（高温需求 A1）。先前的研究表明，HTRA1 启动子区域的多态性导致 HTRA1 蛋白的过表达。本研究探讨了 HTRA1 过表达在 AMD 发病机制中的作用。通过透射电子显微镜、免疫荧光染色和 Western Blot 分析，生成并表征了在视网膜色素上皮 (RPE) 层中过表达鼠蛋白的 Htra1 转基因小鼠。Htra1 转基因小鼠的 Bruch 膜 (BM) 弹性层比野生型 (WT) 对照组更碎片化且连续性更差。缺乏 N 端结构域的重组 HTRA1 可切割各种细胞外基质 (ECM) 蛋白。随后的 Western Blot 分析显示，与 WT 相比，转基因小鼠的 RPE/脉络膜层中的纤连蛋白片段过表达，纤连蛋白 5 和原弹性蛋白减少。纤连蛋白 5 通过促进弹性纤维组装和成熟对弹性发生至关重要。总之，我们的数据表明 HTRA1 过表达通过纤连蛋白 5 的切割导致 BM 中弹性发生改变。它强调了 ECM 相关蛋白在 AMD 发展中的重要性，并将 HTRA1 与其他 AMD 风险基因（如纤连蛋白 5、纤连蛋白 6、ARMS2 和 TIMP3）联系起来。
