Abstract
Purpose: :
The orchestration of epithelial morphogenesis during eye development requires the exquisite degree of precision of varied signaling pathways to define where tissues of the eye form and how individual cells within the eye differentiate. Pinin (Pnn), a nuclear speckle-associated protein, has been shown to impact eye development and epithelial integrity. We have recently elucidated Pnn’s involvement in the modulation of the Wnt pathway. Wnt signaling, acting through Tcf/Lef family of transcription factors, plays a crucial role in both eye development and epithelial homeostasis. Here, we investigated how conditional inactivation of Pnn affects epithelial morphogenesis through its interaction in the Wnt pathway.
Methods: :
Pnn was inactivated in epithelium, by mating mice harboring floxed Pnn alleles with mice expressing Cre-recombinase under the control of the Wnt-1, Sonic hedgehog (Shh) or Keratin-14 promoters.
Results: :
The deletion of Pnn within epithelia resulted in obvious epithelial dysplasia. Mutant tissues exhibited altered expression of several markers of epithelial differentiation. Pnn depletion within epithelial cells led to upregulated Tcf/Lef reporter (Topgal) activity and misregulated expression of β-catenin. Expression Wnt-regulated genes, was significantly disrupted in mutant epithelia. Co-immunoprecipitation assays of Pnn-depleted cells revealed a decreased association of β-catenin with C-terminal binding protein 2 (CtBP2). CtBP proteins have been shown to bind to Pnn and be a key transcriptional regulator of Wnt target genes.
Conclusions: :
Pnn is required for epithelial morphogenesis and epithelial differentiation and that Pnn’s role in epithelial morphogenesis and development may involve its ability to regulate the activity of key mediators of Wnt signaling pathway perhaps through influencing CtBP2 association with β-catenin complex.
Keywords: cell adhesions/cell junctions • signal transduction • cornea: basic science