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Time-Lapse Videos of Actin Dynamics

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Our major interest is in actin dynamics in dendritic spines, shown in the top set of movies. Recordings of actin dynamics in growth cones of developing neurons and in non-neuronal cells are shown further down this page. Unless otherwise stated this data is taken from Fisher et al. 1998 Neuron 20:847-854.

ACTIN DYNAMICS IN DENDRITIC SPINES

 

(2.1 MB). A neuron from rat hippocampus that had been transfected to express GFP-actin and maintained in cell culture for 4 weeks until it had developed dendritic spines in which actin accumulates at high concentrations. The bright fluorescence at top left is part of the cell body where actin is synthesized. The dendritic spines are the bright dots on the dendrites (which extend to the right of the cell body).

  (6 MB). The same neuron as in the above figure but presented at two magnifications: first low magnification to show the cell body and dendrites, then zoomed to show a limited section of dendrites. Notice the enormous number of spines on the dendrites of these neurons each marking the site of an excitatory synapse, and their rapid actin-based motility which over this time-scale consists of changes in spine shape (not spine number).
  (1.6 MB). Taken from a recording of another neuron from a different culture, this higher magnification video sequence shows the nature of actin dynamics in dendritic spines in detail. Notice the motile actin-rich protrusions extending from the head of the spine. Their rapid movements occur even though most of them are contacted by presynaptic terminals.

 

ACTIN DYNAMICS IN GROWTH CONES
  (3.2 MB). Growth cone of a hippocampal neuron after 48 hours in dispersed cell culture. Actin is concentrated in the palm of the growth cone and forms motile filopodia and lammelipodia. Note the far lower actin levels in the shaft of the growing axon behind the growth cone.
  (4 MB). Another hippocampal neuron growth cone with well-marked filopodial activity. (Unpublished recording)

 

ACTIN DYNAMICS IN FIBROBLASTIC CELLS

   (861 KB). This sequence shows the edge of a rat embryo fibroblast that was transfected with actin tagged with green fluorescent protein (GFP­actin). The tagged actin gets incorporated into actin filaments so that they are visible inside the living cell when it is examined with a fluorescence m icroscope. Notice that actin can support two distinct kinds of structures - the highly motile ones at the edge of the cell, where actin polymers are rapidly forming and dissociating again, and relativelt stable ones like the thick bundles of filaments (stress fibres) deeper in the cell. Unpublished recording).
  (2.2 MB). A rat embryo fibroblast migrating toward a "wound" (an area of the culture close by where the cells were scrapted off the cover slip). The area of membrane ruffling at the leading edge of the cell is rich in dynamic actin while the stress fibres in the body of the cell change configuration much less quickly demonstrating the "semi-conservative" way that actin mediates between structural stability and plasticity.