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Sam Charles Kwiatkowski, Peter Y Lwigale; PlexinD1 is required for Vascular Patterning in the periocular region and Establishment of Corneal Avascularity. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3531.
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Signaling of the plexinD1 receptor and Semaphorin3 (sema3) ligands underlies various neurovascular-patterning events during embryonic development. Previously we showed that PlexinD1 mRNA is expressed by angioblasts and blood vessels during ocular vasculogenesis in patterns that suggest its involvement with Sema3 ligands that are concurrently expressed in the anterior eye. In this study, we determine the role of PlexinD1 during vascular patterning in the anterior eye.
RNA and protein analysis were used to establish late-stage vascular patterning events in transgenic Tie1:H2B-eYFP quail embryos. Gene knock down using viral constructs containing mCherry reporter and either scrambled shRNA or PlexinD1-shRNA was used to study PlexinD1 function. Vascular patterning was analyzed by immunohistochemistry in whole-mount or sectioned eyes.
During late stages of ocular development, YFP-positive vasculature formed in the pericorneal region and iris. All the blood vessels in the anterior eye showed robust expression of PlexinD1 mRNA. Eyes expressing mCherry-PlexinD1-shRNA exhibited two phenotypes by embryonic day (E)12. First, ectopic vascularization was evident in the presumptive iris, accompanied with profuse hemorrhaging in the anterior chamber. Second, ectopic vascularization was observed in the periphery of the cornea, which is never vascularized during development. Neovascularization of the cornea coincided with the formation of the limbal vasculature in control embryos. Neither phenotype was observed in control embryos expressing scrambled-shRNA.
The expression of PlexinD1 by blood vessels during ocular development and the defects resulting from its knock down indicate that it plays a critical role during vascular patterning in the limbus and iris, and it is also essential for corneal avascularity. PlexinD1 may be involved in vascular response to anti-angiogenic Sema3 signaling that guide the iris and limbal blood vessels. Therefore PlexinD1 may provide a target for treatment of neovascularization of the cornea or iris and other vascular defects such as hemorrhaging or hyphema of the anterior chamber.
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