title: Let it flow: Morpholino knockdown in zebrafish embryos reveals a pro-angiogenic effect of the metalloprotease meprin alpha2.
abstract: BACKGROUND
  Meprin metalloproteases are thought to be involved in basic physiological functions such as cell proliferation and tissue differentiation. However, the specific functions of these enzymes are still ambiguous, although a variety of growth factors and structural proteins have been identified as meprin substrates. The discovery of meprins alpha(1), alpha(2) and beta in teleost fish provided the basis for uncovering their physiological functions by gene silencing in vivo.
  
  
  RESULTS
  A Morpholino knockdown in zebrafish embryos targeting meprin alpha(1) and beta mRNA caused defects in general tissue differentiation. But meprin alpha(2) morphants were affected more specifically and showed severe failures in the formation of the vascular system provoking the hypothesis of a pro-angiogenic effect. The blood circulation was largely diminished resulting in erythrocyte accumulation. These phenotypes mimic a previously described VEGF-A morphant, revealing a possible role of meprin alpha in VEGF-A activation. Indeed, human recombinant meprin alpha processed the vascular endothelial growth factor-A (VEGF-A) specifically, revealing the same cleavage products detectable for VEGF from zebrafish whole lysate.
  
  
  CONCLUSIONS
  Our results demonstrate that meprin metalloproteases are important for cell differentiation and proliferation already during embryogenesis, predominantly by the activation of growth factors. Thus, we conclude that meprins play a significant role in VEGF-A processing, subsequently regulating angiogenesis. Therefore, meprin alpha might be a new therapeutic target in cardiovascular diseases or in tumor growth inhibition.
authors.affiliation: Institute of Zoology, Cell and Matrix Biology, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Schütte
authors.forename: Jana
authors.initials: J
authors.lastname: Hedrich
authors.forename: Walter
authors.initials: W
authors.lastname: Stöcker
authors.forename: Christoph
authors.initials: C
authors.lastname: Becker-Pauly
mesh_terms: D043925:Angiogenesis Inducing Agents; D000818:Animals; D055785:Gene Knockdown Techniques; D008666:Metalloendopeptidases / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000819:agonists; D015027:Zebrafish / Q000196:embryology*
chemical_list: D043925:Angiogenesis Inducing Agents; D009025:Morpholines; D042461:Vascular Endothelial Growth Factor A; D008666:Metalloendopeptidases; C053833:meprin A