title: Mitochondrial fission and fusion in Dictyostelium discoideum: a search for proteins involved in membrane dynamics.
abstract: BACKGROUND
  Mitochondrial morphology is maintained by two distinct membrane events -fission and fusion. Altering these conserved processes can disrupt mitochondrial morphology and distribution, thereby disrupting the organelle's functionality and impeding cellular function. In higher eukaryotes, these processes are mediated by a family of dynamin-related proteins (DRP's). In the lower eukaryotes, for instance Dictyostelium discoideum, mitochondrial fission and fusion have been implicated but not yet established. To understand the overall mechanism of these dynamics across organisms, we developed an assay to identify fission and fusion events in Dictyostelium and to assess the involvement of the mitochondrial proteins, MidA, CluA, and two DRP's, DymA and DymB.
  
  
  RESULTS
  Using laser scanning confocal microscopy we show, for the first time, that lower eukaryotes mediate mitochondrial fission and fusion. In Dictyostelium, these processes are balanced, occurring approximately 1 event/minute. Quantification of the rates in midA-, cluA-, dymA-, or dymB- strains established that MidA appears to play an indirect role in the regulation of fission and fusion, while the DRP's are not essential for these processes. Rates of fission and fusion were significantly reduced in cluA-cells, indicating that CluA is necessary for maintaining both fission and fusion.
  
  
  CONCLUSIONS
  We have successfully demonstrated that Dictyostelium mitochondria undergo the dynamic processes of fission and fusion. The classical mediators of membrane dynamics - the DRP's - are not necessary for these dynamics, whereas CluA is necessary for both processes. This work contributes to our overall understanding of mitochondrial dynamics and ultimately will provide additional insight into mitochondrial disease.
authors.affiliation: Biology Department, University of Central Arkansas, Conway, AR 72035, USA.
authors.forename: Brixey G
authors.initials: BG
authors.lastname: Schimmel
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Berbusse
authors.forename: Kari
authors.initials: K
authors.lastname: Naylor
mesh_terms: D004023:Dictyostelium / Q000502:physiology*; D034281:Dynamins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000502:physiology*; D063154:Mitochondrial Dynamics; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C106952:CluA protein, Dictyostelium discoideum; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D015800:Protozoan Proteins; D008780:Methyltransferases; D034281:Dynamins; C117420:dynamin A protein, Dictyostelium discoideum