Abstract 105: Proprotein Convertase Subtilisin/kexin Type 6 (Pcsk6) Plays A Role In Angiogenesis Regulation

Background: PCSK6 cleaves and activates growth factors involved in cell differentiation and Pcsk6-/- mice exhibit 25% embryonic lethality, while surviving offspring have blindness and cyclopia. We have shown that PCSK6 localizes to vascular smooth muscle cells of intra-plaque neovessels. We therefore hypothesize that the processes of angiogenesis, atherosclerosis and plaque neovascularisation share common molecular regulators and that PCSK6 plays a role in these processes. Methods: Association between SNPs near the PCSK6 gene and levels of 90 plasma proteins was tested using data from 30,931 individuals in the SCALLOP consortium. Associations of angiogenic factors with PCSK6 (transcriptomic and proteomic) and patient symptomatology were explored in a biobank of plaque endarterectomies (BiKE). Morpholino technology was used for Pcsk6 knockdown in zebrafish, coupled with vascular phenotype studies. Pcsk6-/- mice were used to study the expression of vasculogenesis related genes and vascular morphology at baseline (12 weeks). Results: Rs7178801 and rs11639051 in the PCSK6 gene were found to relate to plasma PDGFB and VEGFD levels. TGFB2, VEGFA, VEGFC, PDGFA and PLAUR associated with patients symptomatology in BiKE and correlated with PCSK6 levels. Gross phenotypic and histological examination of zebrafish embryos with ablated PCSK6 showed improper peripheral vascular patterning of intersegmental vessels along with cerebral and myocardial haemorrhage hemorrhage. Expression of angiogenic factors; Vegfa, Vegfb, Angpt1 and Tgfb2 were altered in the heart, liver and adipose tissue in Pcsk6-/- mice. Vessel density, length and branch numbers were reduced in the Pcsk6 -/- compared to the controls in the superficial but more significantly in the deep peripheral vessels. The smooth muscle cell coverage of the retinal vasculature was also reduced in the Pcsk6 -/- mice vs controls and Pdgfa was significantly downregulated compared to controls in mouse retinas. Conclusions: PCSK6 associates with levels of angiogenic factors on the genetic, transcriptomic and proteomic level. Lack of Pcsk6 in mice and zebrafish led to vascular patterning defects. Further planned studies will examine PCSK6 in pathological neovascularization.