Fig. 5.

Mechanisms for ectopic lumen formation through post-mitotic midbody mispositioning. During normal cystogenesis, the mitotic spindle is positioned perpendicular to the apical–basal axis, followed by asymmetric furrow ingression for apical delivery of the midbody to ensure maintenance of a single lumen (A). Loss of mitotic spindle orientation (B) or loss of asymmetric furrow ingression (C) can lead to failure in apical midbody positioning and an ectopic lumen is formed. Moreover, we propose a new mechanism in which cytokinesis occurs earlier, and abscission takes place before the midbody reaches its luminal position (D). Midbodies (MBs) from previous cell divisions remain at the apical surface. Apical membrane, red; γ-tubulin, dark red; nuclei and chromosomes, blue; midbody and midbody remnants, green. Adapted from Jaffe et al. (2008). This figure is published under a Creative Commons BY-NC-SA license (https://creativecommons.org/licenses/by-nc-sa/3.0/).