Autonomously migrating cytoplast

Movie# E2951
Movie Still
  An anucleate cytoplast--a piece of lamellipodium detached from its parent cell--is able to migrate autonomously, without a nucleus, golgi aparatus, or microtubules.

Cytoplast Retraction Fiber Dynamics

    Movie# E3090
Movie Still
   This sequence shows a cytoplast in the process of forming. Early in the sequence the cytoplast is still attached by a retraction fiber to its parent cell. As the retraction fiber breaks, the cytoplast is suddenly released from the parent cell. The cytoplast then reabsorbs the retraction fiber and migrates autonomously.

Lysosome and Mitochondria Transport

    Movie# E3244
Movie Still
  A more fully differentiated epidermal cell. The nucleus and nucleoli are on the left. The footage is high-resolution Nomarski time-lapse. It shows the intracellular movements of lysosomes and mitochondria. The lysosomes are the small refractile spherical objects near the nucleus. The mitochrondria are the more elongate elipsoidal organelles. The mitochrondria are moved along microtubules by microtubule-based transport motors.

Lamellipodial Action in Wound Closure

    Movie# E3638
Movie Still
  The sequence shows epidermal cells at the edge of an epithelial sheet in cutlture. One can see vigorous lamellipodial activity at the edge of the cell cluster. Lysosomes and elongated mitochondrial are seen near the nucleus. This lamellipodial activity is involved in wound closure; in culture the edge of the epithelial sheet is in a chronic wound state.

Actin nucleation and Retrograde Flow

    Movie# E3807
Movie Still
  This sequence shows actin nucleation on the dorsal surface of an advancing lamellipodium. Small actin nucleations have been termed inductipodia in nerve growth cones, since they can be induced by latex beads landing of the cell surface. Gold beads also elicit this behavior. However, in these cells, the structures are forming spontaneously. One can also see small retrograde flows of actin occuring from the distal margin of the advancing lamellipodia.

Mechanics of Epidermal Migration

    Movie# E3927
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  This is a migrating epidermal cell showing vigorous lamellipodial ruffling more than 180 degrees around its circumferance. The cell becomes elongated into a canoe shape. The mechanical tension generated by the lamellipodia appears to stretch the cell into an elongated form. The lamellipodia in the anterior region of the cell are opposed by a lamellipodium in the trailing region of the cell. This may account for the persistance of the cells motion in a forward direction. All of the cells organelles-- lysozomes, mitochondria, endoplasmic reticulum--are localized with microtubules around the cell body at the trailing edge of the cell.

Endoplasmic Reticulum Extension

    Movie# E4043
Movie Still
  This sequences shows an apidermal cell loaded with a florescent lipid diOC-6. diOC-6 is a vital stain for the endoplasmic reticulum and mitochondria. In this sequence one sees the extension of ER tubules along microtubules into the middle part of the lamellipodium. These extensions of endoplasmic reticulum appear to be pushed back towards the cell body by the retrograde flows of actin in lamellipodia.

Stationary Actin Nucleation

    Movie# E3971
Movie Still
   This sequence is complementary to the sequence (E4043) showing retrograde flow of ER. The clip shows stationary epidermal cells with copious retrograde flow of actin. Actin-myosin networks initiate at the cell periphery and flow towards the cell body. Even though actin-nucleation and retrograde flow are taking place, the cells remain stationary with respect to their substrata.

Ruffling in an Anucleate Cytoplast

    Movie# E4151
Movie Still  The sequence shows a cytoplast which is adhering to a sub-stratum in its central portion. It is also connected by a retraction fiber to its central cell. The cytoplast is engaging in vigourous protrusive activity around its periphery. The small lamellipodia are undergoing ruffling--extensions, folding back, and re-entry of the the protrusion into the main process of the cell. This demonstrates that an anucleate fragment of a cell has the capacity to nucleate actin, engage in ruffling, and retrograde flows. Other sequences (E2951) show that these fragments have the capacity to undergo directional locomotion.

 

last updated 3/21/00 (JAR)