Background: Ryk acts as a Wnt receptor in several processes, including mouse neuronal development. Results: Ryk interacts with Wnt11 in zebrafish convergent extension and with Vangl2 in mouse cochlear development and neural tube closure. Conclusion: Ryk is required for Wnt/planar cell polarity signaling during mammalian development and signals via Vangl2 and RhoA. Significance: This study extends our knowledge of signaling downstream of Ryk.

Hyperinsulinemia in diabetes mellitus is a significant risk factor in the development of atherosclerosis and early restenosis after balloon angioplasty. These manifestations could be mediated by the ability of insulin to potentiate the cellular proliferative and reparative response of vascular cell types to local stimuli. Here we demonstrate that insulin stimulates DNA synthesis in aortic endothelial cells. Reverse transcription-polymerase chain reaction and Northern blotting revealed that insulin induces the expression and transcriptional activity of the immediate early gene and zinc finger transcription protein, early growth response factor-1 (Egr-1). Western immunoblot analysis revealed that insulin-inducible Egr-1 expression was inhibited using phosphorothioate-specific antisense oligonucleotides targeting Egr-1 mRNA. These agents blocked endothelial cell DNA synthesis stimulated by insulin in a dose-dependent manner and inhibited the capacity of insulin to potentiate the reparative response of endothelial cells to mechanical injury in vitro. These oligonucleotides also attenuated wound repair in smooth muscle cells. DNA synthesis induced by insulin was suppressed by inhibitors of two upstream activators of Egr-1, extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-phosphate (PI 3-K), whereas p38 kinase inhibitors had no effect. These present findings demonstrate that insulin-inducible DNA synthesis and repair after injury are processes critically dependent upon the activation of Egr-1. Additionally, they implicate this transcription factor as a potential target for the inhibition of restenosis in diabetics.

Ryk is a member of the receptor tyrosine kinase (RTK) family of proteins that control and regulate cellular processes. It is distinguished by binding Wnt ligands and having no detectable intrinsic protein tyrosine kinase activity suggesting Ryk is a pseudokinase. Here, we show an essential role for Ryk in directing morphogenetic events required for normal cardiac development through the examination of Ryk-deficient mice. We employed vascular corrosion casting, vascular perfusion with contrast dye, and immunohistochemistry to characterize cardiovascular and pharyngeal defects in Ryk embryos. Ryk mice exhibit a variety of malformations of the heart and outflow tract that resemble human congenital heart defects. This included stenosis and interruption of the aortic arch, ventriculoarterial malalignment, ventricular septal defects and abnormal pharyngeal arch artery remodelling. This study therefore defines a key intersection between a subset of growth factor receptors involved in planar cell polarity signalling, the Wnt family and mammalian cardiovascular development.