Cytokinesis is the final chapter of cell division and its last page is abscission, the physical separation of two daughter cells. During cytokinesis of vertebrate cells, two future daughter cells are connected by an intercellular bridge within which the midbody (MB) is positioned. Since becoming the focus of intense investigations on cytokinesis completion, MB is now perceived as a complicated organelle where multiple pathways for abscission are targeted and coordinated. However, whether post-mitotic midbodies, the midbody derivatives (MB^ds), would be retained by either daughter cell post-abscission remains unexplored. In addition, how cells manage the fate of inherited MB^ds is also unclear or only sketchily proposed. Finally, whether the inherited MB^ds in cells may play non-cytokinetic roles is also unaddressed.

In the first chapter, I review the historical and current understanding of MBs, with emphasis on their roles in cytokinesis whereas potential non-cytokinetic roles are also covered. In the second chapter, the aforementioned three questions are sequentially addressed. First, the newly-formed MB^d appears to be inherited by the daughter cell with the older centrosome. Second, MB^ds are not only inherited but also accumulated in cancer and pluripotent stem cells, but not in normal somatic (differentiated) cells. In normal somatic cells, MB^ds are within membrane-bound compartments for lysosomemediated degradation via autophagosome engulfment. This partially explains why MB^d-accumulation is rarely observed in these cells. In contrast to the previous model, colleagues and I showed that MB^d-accumulation correlates well with the autophagosomal-lysosomal activity, but not with the proliferation rate. Finally, the experimental increase of MB^d levels appears to enhance the anchorage-independent growth in cancer cells and the efficiency of reprogramming in fibroblasts. In the last chapter, I conclude our findings and discuss future directions in two aspects.