Figure 13.

Extension ladder model for shortening actin cables in Drosophila nurse cells. During stage 10B of oogenesis (top), overlapping actin bundles (cables) extend from the plasma membrane toward the lobed nucleus. These cables are in their extended form much like an extension ladder at its maximum length. During nurse cell dumping (stage 11, middle), cell volume is reduced but nuclear volume is not. As the distance between the nuclear envelope and the plasma membrane is reduced, individual bundles in the actin cables are forced to slide past one another, reducing the overall length of the cable. After dumping (bottom), the nuclear envelope to plasma membrane distance is reduced to a minimum, resulting in maximal overlaps among the actin bundles. These cables are in their most compressed form much like an extension ladder in its most retracted form where modules exhibit maximum overlap.