PI3K–AKT signaling is regulated by PDGFRα during lens development.

(A–B) AKT phosphorylation was strongly stimulated by PDGFA but weakly by FGF2 in immortalized lens cells. In contrast, FGF2, but not PDGFA, induced strong ERK phosphorylation. (C) pAKT was down-regulated in mutant lenses lacking Pdgfrα (Le-Cre;Pdgfrαf/f) and in lenses expressing a mutant allele of Pdgfra that prevents interaction with PI3K (Le-Cre; Pdgfrαf/ΔPI3K). However, ERK phosphorylation was unaffected in either Pdgfra mutant. Staining of the anterior progenitor markers Ki67, Foxe3, and E-cadherin and posterior differentiation markers p57, C-maf, and Jag1 indicated the anterior shift of the transitional zone in these mutants (arrows). (D–E) The relative fluorescent intensities of pAKT and pERK at the transitional zones of the lenses. One-way ANOVA test, n = 3 embryos for each genotype. (F) The percentage of Ki67+ cells in the lens epithelium. One-way ANOVA test, n = 3 embryos for each genotype. (G) Quantification of the lens perimeter covering the anterior epithelium versus that of the posterior lens fiber. One-way ANOVA test, n = 5 embryos for Le-Cre;Pdgfrαf/f and control, n = 6 for Le-Cre; Pdgfrαf/ΔPI3K. Scale bar: 100 μm. The numerical data used in panels D, E, F, and G are included in S1 Data. AKT, Protein kinase B; C-maf, MAF BZIP Transcription Factor; ERK, Extracellular Signal-Regulated Kinase; FGF2, fibroblast growth factor 2; Foxe3, Forkhead Box E3; Jag1, Jagged 1; N.S., not significant; pAKT, phospho-AKT; PDGFRα, Platelet-Derived Growth Factor Receptor α; pERK, phospho-ERK; PI3K, Phosphoinositide 3-kinase.