ROR2 in Post-Natal Vessel Formation

Vessel formation requires a precise orchestration of morphometric and molecular events controlled by a multitude of angiogenic factors and morphogens. Growing evidence has shown that Wnt/PCP pathway is important for vessel formation. We previously demonstrated that ubiquitin ligase E3 PDZRN3 drives non-canonical Wnt/PCP signaling to control post-natal angiogenesis in the retina. Endothelial cell polarity is essential to control vascular properties and endothelial cell polarization. Orphan tyrosine receptor kinase ROR2 has been described to regulate Wnt/PCP signaling. The goal of this study was to investigate the role of ROR2 during vascular formation and its role in EC polarity. For this purpose we first analyzed the expression of ROR2 during the kinetic of vascular formation in the retina. After in toto immunofluorescence staining, ROR2 is observed in different cells in the retina and in CD31+ cells. By Western blot and qRT-PCR, we showed that ROR2 is strongly expressed at P4-P7 and decreased after P8. To analyze the role of ROR2 in the endothelium, transgenic mice deleted for ROR2 specifically in the endothelium (CDH5-iCre;ROR2F/F and Pdgfb-iCre; ROR2F/F mice) were generated. The retinas of pups sacrificed 5, 7 and 11 days after birth were immunostained (CD31, isolectin B4, NG2, SMA, ColIV, KI67) to study the kinetics of vascular plexus formation. Deletion of ROR2 gene induced a significant decrease in vessel plexus formation at P5, P7 and P11 in Pdgfb-ROR2iECKO and CDH5-ROR2iECKO mice compared to littermates. This study shows that ROR2 is required for the formation of primary but also ternary vascular network. Investigation of the ROR2 signaling and molecular mechanisms are under investigation to understand whether and how ROR2/PCP pathway could regulate EC properties.