19-P042 Isolation and characterization of putative endothelial progenitor cells in Xenopus

A major goal in regenerative medicine is to understand and ultimately facilitate our body’s ability to repair itself following injury. As a first step toward this goal, we have begun to investigate the molecular and cellular basis of embryonic wound healing, given that embryos have the capacity to heal wounds quickly and completely. Tissue repair resembles embryo morphogenesis in several ways, including cell migration, proliferation and differentiation. In a screen for genes involved in morphogenesis in Xenopus, we identified an Ins(1,4,5)P3 phosphatase (IPP), which impairs embryonic wound healing, suggesting that IP3 signalling plays a role in this process. This finding has motivated us to investigate the role of IP3 signalling during embryonic wound healing, using Xenopus as a model system. Two sets of enzymes regulate this pathway, the IP3 kinases and IPPs. IPP, such as Ins(1,4,5)P3-5 phosphatase (IPP5), promote Ins(1,4)P2 generation, which is an inactive product, while IP3 kinases generate Ins(1,3,4,5)P4, which is involved in calcium release modulation. We have cloned IP3 kinase-B and IPP5-A from Xenopus tropicalis and have begun to investigate theirs effects during embryonic wound healing. By misexpressing IPP5-A we inhibited wound healing while IP3 kinase-B accelerated it during early development in embryonic wound healing assays. Opposite to this effect knocking down IP3 kinase-B we inhibited wound healing. Finally, we are investigating the consequence of these manipulations on the organization of the cytoskeleton such as analyzing microtubules, tau2, or F-actin, moesin and phalloidin-rhodamine, and investigating which pathways are modulated by IP3 signalling during wound healing.