Kjaer-Sorensen, K., Engholm, D.H., Jepsen, M.R., Morch, M.G., Weyer, K., Hefting, L.L., Skov, L.L., Laursen, L.S., Oxvig, C. (2014) Papp-a2 modulates development of cranial cartilage and angiogenesis in zebrafish embryos. Journal of Cell Science. 127(23):5027-37.
Pregnancy-associated plasma protein-A2 (PAPP-A2, pappalysin-2) is a large metalloproteinase, known to be required for normal postnatal growth and bone development in mice. We here report the detection of zebrafish papp-a2 mRNA in chordamesoderm, notochord, and lower jaw of zebrafish (Danio rerio) embryos, and that papp-a2 knockdown embryos display broadened axial mesoderm, notochord bends, and severely reduced cranial cartilages. Genetic data link these phenotypes to insulin-like growth factor binding protein-3 (Igfbp-3) and Bmp signaling, and biochemical analysis show specific Igfbp-3 proteolysis by Papp-a2, implicating Papp-a2 in the modulation of Bmp signaling by Igfbp-3 proteolysis. Knockdown of papp-a2 additionally resulted in angiogenesis defects, strikingly similar to previous observations in embryos with mutations in components of the Notch system. Concordantly, we find that Notch signaling is modulated by Papp-a2 in vivo, and, furthermore, that PAPP-A2 is capable of modulating Notch signaling independently of its proteolytic activity in cell culture. Based on these results, we conclude that Papp-a2 modulates Bmp and Notch signaling by independent mechanisms in zebrafish embryos. In conclusion, these data link pappalysin function in zebrafish to two different signaling pathways outside the IGF system.