Figure 5.

GM130 depletion induces fragmentation of the Golgi ribbon, shortening of the cisternae, and accumulation of tubulovesicular membranes. Control and N309-injected HFs (A and B), and control and G95-overexpressing COS7 cells (C) were processed for EM (A and C) and morphometric analysis (B), as described in Materials and Methods. CHO and ldlG cells (D–G) were analyzed by EM serial sectioning (D and E) or EM tomography (F and G). Bottom panels in D and E show superimposition of Golgi (blue) and tubule and vesicle (green) profiles in six consecutive serial sections. Bottom panels in F and G show 3D EM-tomography reconstructions, with cis-most (red) and trans-most (magenta) cisternae. Vesicles (blue, 50–60 nm; white, 80–90 nm) are represented by software-generated spheres, centered on the center of the vesicles. Bar, 1 μm (A and C–E); 600 nm (F and G). (H) Morphometric analysis of the Golgi area in serial sections from CHO cells, ldlG cells, and ldlG cells expressing GFP-GM130 (see Materials and Methods). Stack coalescence is where two apparently distinct stacks on one section become one stack on the next section. The number of these coalescence events is related to the number of stacks in the sections.