title: Aberrant stalk development and breakdown of tip dominance in Dictyostelium cell lines with RNAi-silenced expression of calcineurin B.
abstract: BACKGROUND
  Calcineurin, the Ca2+/calmodulin-dependent protein phosphatase, plays important roles in various cellular processes in lower and higher eukaryotes. Here we analyze the role of calcineurin in the development of Dictyostelium discoideum by RNAi-mediated manipulation of its expression.
  
  
  RESULTS
  The cnbA gene of Dictyostelium discoideum which encodes the regulatory B subunit (CNB) of calcineurin was silenced by RNAi. We found a variety of silencing levels of CNB in different recombinant cell lines. Reduction of CNB expression in a given cell line was correlated with developmental aberrations. Cell lines with strongly reduced protein levels developed slower than wild type cells and formed short stalks and spore heads with additional tips. Formation of short stalks results from incomplete vacuolization of prestalk cells during terminal differentiation. Expression of the stalk-specific gene ecmB was reduced in mutant cells. Aberrant stalk development is a cell autonomous defect, whereas the breakdown of tip dominance can be prevented by the presence of as low as 10% wild type cells in chimeras.
  
  
  CONCLUSIONS
  Silencing of calcineurin B in Dictyostelium by expression of RNAi reveals an unexpected link between increased intracellular calcium levels, possibly triggered by the morphogen DIF, activation of calcineurin, and the terminal stage of morphogenesis.
authors.affiliation: Institut für Biologie - Mikrobiologie, Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Königin-Luise-Strasse 12-16, 14195 Berlin, Germany. kboeckeler@web.de
authors.forename: Katrina
authors.initials: K
authors.lastname: Boeckeler
authors.forename: Gilbert
authors.initials: G
authors.lastname: Tischendorf
authors.forename: Rupert
authors.initials: R
authors.lastname: Mutzel
authors.forename: Barbara
authors.initials: B
authors.lastname: Weissenmayer
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000235:genetics / Q000502:physiology*; D065095:Calcineurin Inhibitors; D002460:Cell Line; D004023:Dictyostelium / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D015536:Down-Regulation; D009154:Mutation; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D033761:Spores, Protozoan / Q000166:cytology / Q000648:ultrastructure; D019076:Transgenes
chemical_list: D065095:Calcineurin Inhibitors; D015800:Protozoan Proteins; D019703:Calcineurin