• An animated sequence of a cell with GFP tagged corinin, an actin-associated protein during phagocytosis of yeast (red) (mov - 910 KB)
  25.07.2005

• Accumulation of GFP-Arp3 at the border of a phagocytic cup.Arp 3 is a member of the Arp2/3 complex, which nucleates actin polymerization and causes filaments to branch. GFP-Arp3 fluorescence is shown in green, phase contrast of the Dictyostelium cell (mov - 797 KB)
  25.07.2005

• Phagocytosis of yeast particles by a Dictyostelium cell expressing GFP-calreticulin. (mov - 684 KB)
  25.07.2006
  The fluorescent calreticulin as an ER-resident marker visualizes extension of the ER into a phagocytic cup. Confocal sections through the phagocytic cup show the GFP-calreticulin fluorescence in green, superimposed on phase-contrast images in red. Work with calreticulin/calnexin-null mutants has shown that these Ca2+-binding chaperones are important for phagocytic cup extension (Müller-Taubenberger et al., 2001;EMBO J. 20, 6772-6782).

• Motility of Dictyostelium cells on glass by double-view microscopy: (mov - 684 KB)
  25.07.2005
  Dark areas indicate cell-substrate contact. AX2 (left), a mutant lacking 3 actin-binding proteins (right) (1.8 MB). Movement of the mutant cell is less persistent.

• Motility of chemotactically stimulated wild-type cells viewed by RICM (mov - 1,4MB)
  25.07.2005

• Motility of chemotactically stimulated talin-null cells viewed by RICM (mov - 1,8MB)
  25.07.2005

• Two sequences showing redistribution of GFP-coronin (green) in Dictostelium cells orienting in gradients of chemoattractant (mov - 556KB)
  25.07.2005
  Animation 1 The chemoattractant cyclic AMP was applied through a micropipette, which was moved into different positions. Cell shape and pipette positions are seen in phase contrast (red). Frame-to frame intervals: 10 seconds.

• Two sequences showing redistribution of GFP-coronin (green) in Dictostelium cells orienting in gradients of chemoattractant (mov - 556KB)
  25.07.2005
  Animation 2 The chemoattractant cyclic AMP was applied through a micropipette, which was moved into different positions. Cell shape and pipette positions are seen in phase contrast (red). Frame-to frame intervals: 10 seconds.

• Cytokinesis of Dictyostelium wild-type (AX2) cells: (mov - 1,67MB)
  Phase contrast (left) and reflection interference contrast microscopy (RICM,right)

• Accumulation of actin (left) and of the actin-binding protein coronin (right) at the poles of mitotic Dictyostelium cells. (mov - 557KB)
  25.07.2005
  Animation 1: Actin-GFP Each protein was tagged with GFP, and GFP-a-tubulin was expressed in the same cells to visualize the mitotic apparatus. Actin polymerizes primarily at the cell poles. Accordingly, GFP-actin is most strongly accumulated in ruffles at the polar regions of a dividing cell. Coronin mirrors the distribution of F-actin. This particular cell was surrounded by bacteria, which are phygocytosed at the polar regions, each phagocytic cup getting decorated with coronin (One phagosome occupies the cleavage furrow at the end of cytokinesis without preventing separation of the daughter cells).

• Accumulation of actin (left) and of the actin-binding protein coronin (right) at the poles of mitotic Dictyostelium cells. (mov - 557KB)
  25.07.2005
  Animation 2: Coronin-GFP Each protein was tagged with GFP, and GFP-a-tubulin was expressed in the same cells to visualize the mitotic apparatus. Actin polymerizes primarily at the cell poles. Accordingly, GFP-actin is most strongly accumulated in ruffles at the polar regions of a dividing cell. Coronin mirrors the distribution of F-actin. This particular cell was surrounded by bacteria, which are phygocytosed at the polar regions, each phagocytic cup getting decorated with coronin (One phagosome occupies the cleavage furrow at the end of cytokinesis without preventing separation of the daughter cells).

• Cytokinesis of a myosin II-null cell attached to a glass surface (mov - 379KB)
  25.07.2005
  Myosin II is considered to be important for the formation of a contractile ring in the cleavage furrow region. However, myosin II-null cells of Dictyostelium can complete cytokinesis when they are attached to a solid surface, indicating that under these conditions other proteins are sufficient for cleavage. One of these proteins is cortexillin (see next movie). This cell express GFP-a-tubulin to visualize the mitotic apparatus. (Weber et al., 2000).

• Seperation of two different actin-binding proteins during cytokinesis of Dictyostelium cells (mov - 285KB)
  25.07.2005
  Animation 1: Arp3- GFP, GFP-tagged Arp3 localizes to ruffles at ihe cell poles. Arp3 is a constituent of the Arp2/3 complex insolved in nucleation of actin polymerization and in filament branching. Right:GFP-cortexillin I, a protein forming heterodimers with cortexillin II. Cortexilins are actin-bunding proteins that localize to the cleavage furrow. Gene knock-outs have shown that cortexillins are required for proper cleavage furrow formation (Weber et al. 1999, Stock et.al.1999)

• Seperation of two different actin-binding proteins during cytokinesis of Dictyostelium cells (mov - 379KB)
  25.07.2005
  Animation 2:Cortexillin I-GFP) GFP-tagged Arp3 localizes to ruffles at ihe cell poles. Arp3 is a constituent of the Arp2/3 complex insolved in nucleation of actin polymerization and in filament branching. Right:GFP-cortexillin I, a protein forming heterodimers with cortexillin II. Cortexilins are actin-bunding proteins that localize to the cleavage furrow. Gene knock-outs have shown that cortexillins are required for proper cleavage furrow formation (Weber et al. 1999, Stock et.al.1999)

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