Figure 1. Two models have been proposed to explain transport through the Golgi.

(A) In cisternal maturation, cargo (blue) moves across the stack of cisternae (three shown in each Golgi) and Golgi enzymes (not shown) move between the compartments to process the cargo before it exits the stack. (B) Lavieu et al. propose a model called rim progression, in which the edges of the cisternae (known as rims) move across the stack, while the central regions of the cisternae remain in place. They base this model on the observation that large protein aggregates called ‘staples’ (black bars in A and B)—which span the cisternae—remain stationary in the central regions, while soluble cargo (blue) progress across the stack via the rims.