Plexin signalling and vascular development in the zebrafish, danio rerio

Date
2008
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Proper development of the cardiovascular system is critical for the survival of an embryo and homeostasis in the adult. Zebrafish are an excellent model system for cardiovascular studies due in part to their externally fertilized, rapidly developing embryos. These studies utilized the out of bounds ( obd) genetic mutant, which shows defects in patterning of the angiogenic intersegmental vessels of the trunk. Previous mapping found that aberrant vascular patterning in the obd mutant is due to defects in the PlexinDl receptor. Further characterization of plexinDJ found it is expressed throughout the vasculogenic and angiogenic vessels of the zebrafish from ~10 somites (s) to 72 hours post fertilization (hpf), in the bulbous arteriosus by 72 hpf, and the forebrain between 30 and 43 hpf. PlexinDl may function in lymphatic development as angiography shows that obd mutants also lack a patent thoracic duct. Plexins and Neuropilins are receptors for Semaphorin ligands and are well known for their role in regulating the migration of axonal growth cones. However, nothing is known of the PlexinDl signalling pathway. As such, the focus of this thesis was to identify components of the PlexinD 1 signalling pathway in order to elucidate the role it plays in vascular migration. The axonal growth cone and migrating tip cell of endothelial cells are homologous structures and it was hypothesized that Plexins function in the same manner in both systems. An expression screen was first performed with 10 genes downstream from neuronal Plexins to determine if any had vascular expression. Most showed ubiquitous expression with increased levels of expression in the nervous system. Since no candidates were uniquely expressed in the vascular system, a pull-down assay with tagged versions of the intracellular region of PlexinD 1 and various pools of prey protein were used in an attempt to identify direct binding partners. Further analysis of two cytosolic tyrosine kinases identified in one pull­down assay, Zeta associated protein-70 (ZAP-70) and Spleen tyrosine kinase (SYK), resulted in the identification of a novel role for these genes in the sprouting of trunk intersegmental vessels through the vegfa pathway. Although components of the PlexinD 1 pathway were not identified, this research has laid the groundwork for future studies to further our knowledge of zebrafish angiogenesis.
Description
Bibliography: p. 160-171
Some pages are in colour
Keywords
Citation
Christie, T. L. (2008). Plexin signalling and vascular development in the zebrafish, danio rerio (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/2574
Collections