Spry1 and Spry2 are necessary for eyelid closure

Sproutys (Sprys) are downstream targets and negative feedback regulators of the FGF-Ras-ERK signaling pathway. Our previous studies have shown that Spry1 and Spry2, through negative modulation of FGF-ERK signaling, allow lens vesicle separation from the overlying ectoderm and regulate corneal epithelial proliferation. Here we show that Spryl and Spiy2 are necessary for eyelid closure. Murine palpebral conjunctival epithelial cells that differentiate as inner eyelids and adjacent mesenchymal cells express Spry1 and Spry2 prior to eyelid closure. Conditional deletion of both Spryl and Spiy2, but not either one alone, in the ocular surface epithelial cells result in the EOB (eyes open at birth) phenotype suggesting redundant roles for these proteins during eyelid closure. Spry mutant eyelids show increased proliferation of conjunctival epithelial cells with concomitant induction of FGF targets, Erm, Pea3 and Dusp6 and elevated ERK phosphorylation. Peridermal cells at the leading edge of Spry-mutant eyelids showed reduced c-Jun, but not ERR, phosphorylation, reduced F-actin polymerization and reduced motility in vitro. Spry mutant eyelids also showed disruptions in epithelial mesenchymal interactions reflected in the enhanced mesenchymal Spryl and Spry4 expression, disaggregation of BMP4-positive mesenchymal cells and loss of Shh in the eyelid epithelium. Spry mutant eyelids also showed increased Wnt signaling and reduced expression of Foxc1 and Foxc2, two transcription factors previously shown to be necessary for eyelid closure. Collectively, our results show that conjunctival epithelial Spryl and Spry2 redundantly promote eyelid closure by (a) stimulating ERR-independent, c-Jun-mediated peridermal migration, (b) suppressing conjunctival epithelial proliferation through FGF-ERK signaling, (c) mediating conjunctival epithelial-mesenchymal interactions and (d) maintaining expression of Foxcl and Foxc2. (C) 2013 Elsevier Inc. All rights reserved.