Department of Surgery, Creighton University, Omaha, Nebraska, USA.
Invest Ophthalmol Vis Sci. 2011 Aug 29;52(9):6887-97. doi: 10.1167/iovs.11-7531.
The studies reported here were performed to analyze the roles of Sproutys (Sprys), downstream targets and negative feedback regulators of the fibroblast growth factor (FGF) signaling pathway, in lens and corneal differentiation.
Spry1 and -2 were conditionally deleted in the lens and corneal epithelial precursors using the Le-Cre transgene and floxed alleles of Spry1 and -2. Alterations in lens and corneal development were assessed by hematoxylin and eosin staining, in situ hybridization, and immunohistochemistry.
Spry1 and -2 were upregulated in the lens fibers at the onset of fiber differentiation. FGF signaling was both necessary and sufficient for induction of Spry1 and -2 in the lens fiber cells. Spry1 and -2 single- or double-null lenses failed to separate from the overlying ectoderm and showed persistent keratolenticular stalks. Apoptosis of stalk cells, normally seen during lens vesicle detachment from the ectoderm, was inhibited in Spry mutant lenses, with concomitant ERK activation. Prox1 and p57(KIP2), normally upregulated at the onset of fiber differentiation were prematurely induced in the Spry mutant lens epithelial cells. However, terminal differentiation markers such as β- or γ-crystallin were not induced. Corneal epithelial precursors in Spry1 and -2 double mutants showed increased proliferation with elevated expression of Erm and DUSP6 and decreased expression of the corneal differentiation marker K12.
Collectively, the results indicate that Spry1 and -2 (1) through negative modulation of ERKs allow lens vesicle separation, (2) are targets of FGF signaling in the lens during initiation of fiber differentiation and (3) function redundantly in the corneal epithelial cells to suppress proliferation.
本研究旨在分析 Sprouty（Spry）在晶状体和角膜分化中的作用，Sprouty 是成纤维细胞生长因子（FGF）信号通路的下游靶标和负反馈调节因子。
利用 Le-Cre 转基因和 Spry1 和 -2 的 floxed 等位基因，在晶状体和角膜上皮前体细胞中条件性缺失 Spry1 和 -2。通过苏木精和伊红染色、原位杂交和免疫组织化学评估晶状体和角膜发育的变化。
Spry1 和 -2 在纤维分化开始时在上皮细胞中上调。FGF 信号对于诱导晶状体纤维细胞中 Spry1 和 -2 的表达是必要和充分的。Spry1 和 -2 单或双敲除晶状体不能与上覆外胚层分离，并显示持续的角膜晶状体柄。在 Spry 突变体晶状体中，正常情况下在晶状体从外胚层脱离时观察到的柄细胞凋亡被抑制，同时 ERK 被激活。Prox1 和 p57（KIP2）在纤维分化开始时正常上调，但在 Spry 突变体晶状体上皮细胞中过早诱导。然而，终末分化标志物如β-或γ-晶体蛋白未被诱导。Spry1 和 -2 双突变体中的角膜上皮前体细胞显示出增殖增加，同时表达 Erm 和 DUSP6 增加，角膜分化标志物 K12 表达减少。
总的来说，这些结果表明 Spry1 和 -2（1）通过负向调节 ERK 允许晶状体泡分离，（2）是纤维分化起始时晶状体中 FGF 信号的靶标，（3）在角膜上皮细胞中冗余地抑制增殖。
