Lens Basement Membrane in SPARC-Null Cataractogenesis

描述（由申请人提供）：骨粘连蛋白（分泌的酸性蛋白，富含半胱氨酸），也称为骨粘连蛋白和BM-40，是一种基质细胞糖蛋白，已显示其调节细胞功能，如细胞周期、细胞形状改变、迁移、粘附、基因表达和ECM产生。无SPARC的小鼠是存活的，但表现出100%白内障。透镜囊是高度发育的透镜基底膜（BM），是一种特殊的ECM结构，其功能是调节透镜上皮细胞的细胞行为和分化。作为位于透镜囊和透镜上皮中的主要细胞-基质调节剂，ECM可能在透镜BM结构、基质组织及其与细胞内途径的连接以及透镜细胞-ECM相互作用中起关键作用，其中的缺陷可能具有显著的病理学后果，例如白内障形成。我们将检验这样的假设，即缺少ECM会导致透镜BM的结构和功能完整性丧失，并导致透镜细胞-ECM相互作用改变，从而导致白内障的发生。 基于我们对晶状体结构和功能的理解，我们提出了三个目标来验证我们的假设：1）晶状体在透镜BM的结构稳定性和组织中起着关键作用。缺乏β-淀粉样蛋白的小鼠将表现出透镜BM组分的改变和受损的透镜囊结构; 2）β-淀粉样蛋白通过其调节粘附蛋白层粘连蛋白1和纤连蛋白的产生以及通过其与它们的相互作用来调节透镜上皮细胞粘附; 3）透镜囊的渗透性在无SPARC的透镜中受损，这部分地促成了该模型中的白内障形成。 在本申请中提出的实验将提供一个理解的作用，ECM成分的组织中，在细胞-ECM相互作用在透镜发展，并在白内障的产生在SPARC-无效的小鼠。

DESCRIPTION (provided by applicant): SPARC (secreted protein acidic and rich in cysteine), also termed osteonectin and BM-40, is a matricellular glycoprotein which has been shown to regulate cell functions such as cell cycle, cell shape change, migration, adhesion, gene expression and ECM production. SPARC-null mice are viable but exhibit cataract with 100% penetrance. Lens capsule, a highly-developed lens basement membrane (BM), is a specialized ECM structure which functions to regulate cell behavior and differentiation of the lens epithelial cells. SPARC, as a major cell-matrix regulator that is localized in the lens capsule and lens epithelium, may play a pivotal role in the lens BM structure, matrix organization and its connections to intracellular pathways, and lens cell-ECM interactions, defects in which can have significant pathological consequences, such as cataract formation. We will test the hypothesis that the absence of SPARC contributes to a loss of the structural and functional integrity of the lens BM, and leads to alteration of lens cell-ECM interactions, that contribute to the generation of cataracts. Based on our understanding of SPARC structure and function, we propose three aims to test our hypotheses: 1) SPARC plays a pivotal role in structural stability and organization of the lens BM. Mice lacking SPARC will exhibit alterations of lens BM components and compromised lens capsule structure; 2) SPARC modulates lens epithelial cell adhesion through its regulation of the production of the adhesive proteins laminin 1 and fibronectin, and by its interaction with them; 3) Lens capsule permeability is compromised in SPARC-null lens, which contributes, in part, to the cataract formation in this model. The experiments proposed in this application will provide an understanding of the role of SPARC in the organization of ECM components, in cell-ECM interactions during lens development, and in the generation of cataracts in SPARC-null mice.