Structure Changes Assoc with Chemotaxis in Dictyostelium

Office Of The Director, Nih

Investigators

Abstract

To complement studies being conducted by NCI investigators to understand the signaling cascades that occur during chemotaxis in Dictyostelium discoideum, we are determining the high-resolution three-dimensional arrangement of vesicles that are observed by fluorescence light microscopy in migrating Dictyostelium. Cells are introduced into plastic capillary tubes under a cAMP gradient to provide conditions of directed cell migration. The capillary tubes are then quickly frozen at high pressure to preserve the cellular ultrastructure. The frozen blocks are freeze-substituted, embedded in plastic, sectioned to a thickness of 0.3 to 0.5 micrometers, stained and analyzed by automated electron tomography in an energy-filtering 300 kV field-emission transmission electron microscope. Experiments are in progress to reconstruct whole cells to visualize ultrastructural differences between the anterior and posterior regions of the migrating amoebae.