Mitotic partitioning of endosomes and lysosomes

Background: Some of the mechanisms underlying cell division and partitioning of the cellular components into the daughter cells are well known. Within the endomembrane system, there is a general cessation of membrane traffic, including endocytosis and endosome fusion, at the onset of mitosis. However, the fate of endosomes and lysosomes during mitosis has been less well studied. Results: Using video and confocal microscopy of living cells, we show here that endosomes and lysosomes remain intact and separate during mitosis. The segregation into daughter cells takes place by coordinated movements, and during cytokinesis, these organelles accumulate in the vicinity of the microtubule organization center. However, partitioning into daughter cells is not more accurate than a calculated stochastic distribution, despite the apparent order to the process. Conclusion: We conclude that partitioning of endosomes and lysosomes is an ordered, yet imprecise, process, and that the organelle copy number is maintained by the daughter cells.