Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA.
Dev Biol. 2011 Dec 1;360(1):30-43. doi: 10.1016/j.ydbio.2011.09.004. Epub 2011 Sep 16.
Morphogenesis and shape of the ocular lens depend on epithelial cell elongation and differentiation into fiber cells, followed by the symmetric and compact organization of fiber cells within an enclosed extracellular matrix-enriched elastic capsule. The cellular mechanisms orchestrating these different events however, remain obscure. We investigated the role of the Rac1 GTPase in these processes by targeted deletion of expression using the conditional gene knockout (cKO) approach. Rac1 cKO mice were derived from two different Cre (Le-Cre and MLR-10) transgenic mice in which lens-specific Cre expression starts at embryonic day 8.75 and 10.5, respectively, in both the lens epithelium and fiber cells. The Le-Cre/Rac1 cKO mice exhibited an early-onset (E12.5) and severe lens phenotype compared to the MLR-10/Rac1 cKO (E15.5) mice. While the Le-Cre/Rac1 cKO lenses displayed delayed primary fiber cell elongation, lenses from both Rac1 cKO strains were characterized by abnormal shape, impaired secondary fiber cell migration, sutural defects and thinning of the posterior capsule which often led to rupture. Lens fiber cell N-cadherin/β-catenin/Rap1/Nectin-based cell-cell junction formation and WAVE-2/Abi-2/Nap1-regulated actin polymerization were impaired in the Rac1 deficient mice. Additionally, the Rac1 cKO lenses were characterized by a shortened epithelial sheet, reduced levels of extracellular matrix (ECM) proteins and increased apoptosis. Taken together, these data uncover the essential role of Rac1 GTPase activity in establishment and maintenance of lens shape, suture formation and capsule integrity, and in fiber cell migration, adhesion and survival, via regulation of actin cytoskeletal dynamics, cell adhesive interactions and ECM turnover.
眼晶状体的形态发生和形状取决于上皮细胞的伸长和分化为纤维细胞，随后纤维细胞在富含细胞外基质的封闭弹性囊内进行对称和紧密的组织。然而，协调这些不同事件的细胞机制仍然不清楚。我们通过使用条件性基因敲除 (cKO) 方法靶向删除表达，研究了 Rac1 GTPase 在这些过程中的作用。Rac1 cKO 小鼠源自两种不同的 Cre（Le-Cre 和 MLR-10）转基因小鼠，其中晶状体特异性 Cre 表达分别在胚胎第 8.75 天和第 10.5 天在晶状体上皮细胞和纤维细胞中开始。与 MLR-10/Rac1 cKO（E15.5）小鼠相比，Le-Cre/Rac1 cKO 小鼠表现出早期（E12.5）和严重的晶状体表型。虽然 Le-Cre/Rac1 cKO 晶状体显示出初级纤维细胞伸长的延迟，但来自两种 Rac1 cKO 品系的晶状体都表现出异常的形状、次级纤维细胞迁移受损、缝合缺陷和后囊变薄，这通常导致破裂。在 Rac1 缺陷型小鼠中，晶状体纤维细胞的 N-钙粘蛋白/β-连环蛋白/Rap1/Nectin 细胞-细胞连接形成和 WAVE-2/Abi-2/Nap1 调节的肌动蛋白聚合受损。此外，Rac1 cKO 晶状体的特征是上皮细胞层缩短、细胞外基质 (ECM) 蛋白水平降低和细胞凋亡增加。总之，这些数据揭示了 Rac1 GTPase 活性在晶状体形状、缝合形成和囊完整性以及纤维细胞迁移、粘附和存活中的建立和维持中的重要作用，通过调节肌动蛋白细胞骨架动力学、细胞粘附相互作用和 ECM 周转。
