Characterization of the Dishevelled Family Proteins in Oxygen-Induced Retinopathy

Abstract

Purpose: : Proliferative retinopathies are the leading cause of blindness in children and working age adults. Disease severity could be ameliorated by specifically targeting pathological neovessels while leaving normal vessels untouched. We found recently that Wnt signaling regulates pathological revascularization in the retina. Dishevelled (Dvl) 1, 2, and 3 are key components of the canonical Wnt pathway relaying signals to downstream targets. In this study, we characterized mutant mice lacking Dvls (Dvl1, Dvl2, and Dvl3) during normal retinal development and in oxygen-induced retinopathy (OIR) to gain a better understanding of the role of Dvls in regulating retinal blood vessel growth.

Methods: : Dvl1-/-, Dvl2-/-, and Dvl3+/- mice and their littermate controls were exposed to 75% oxygen from postnatal day (P) 7 to P12. Dvl3+/- mice were assessed in OIR because Dvl3-/- mice do not survive long after birth. Eyes were dissected at P17, and vaso-obliteration and pathological neovascularization (NV) were quantified. Normal retinal development was characterized by quantifying vascularized area during development as well as assessing adult retinal vasculature in flatmounts and cross sections. Additionally, mRNA expression of Dvls during retinal development was examined in wild type retinas (P1-P17) using RT-qPCR.

Results: : Retinal expression levels of Dvl1 and Dvl3 in wild type mice remain relatively unchanged from P1 to P17. In contrast, Dvl2 shows robust mRNA expression during the first week after birth and gradually decreases as retina matures. Despite normal vascular growth during development, after OIR, Dvl2-/- mice have significantly reduced NV (6.5±1% versus 9.1±0.5%; P≤0.01) at P17 as compared to littermate controls. In contrast, both Dvl1-/- and Dvl3+/- mice exhibit similar levels of NV at P17 after OIR compared to their relative controls.

Conclusions: : Our results demonstrate that Wnt signaling through Dvl2 contributes to pathological retinal NV in a mouse model of OIR. The normal retinal vascular development in Dvl2 KO mice and lack of OIR phenotype in Dvl1 and Dvl3 mutant mice may reflect redundant roles of Dvl 1, 2, and 3 in development and disease.

Keywords: retinal neovascularization • retinopathy of prematurity • retinal development