Cytokinetic abscission is the last step of cell division where two daughter cells are separated. After membrane constriction, the cells remain connected by an intercellular bridge of membrane and microtubules. Abscission is mediated by fission of the microtubules and membrane driven by the ESCRT proteins complex. The spatiotemporal organization of ESCRTs during abscission was mapped in cytokinesis of mammalian tissue-culture-cells. However, little is known about the ESCRTs role during embryonic development. In this study, we tracked the spatiotemporal dynamics of intercellular bridges at different division cycles of developing zebrafish embryos. We found that abscission is delayed prior to the 10th cell cycle. During the first 10 division cycles, cells maintain their intercellular bridges as they enter the following cycle. The 10th division cycle in zebrafish termed MidBlastula-Transition (MBT), and characterized by translation of zygotic genes, appearance of G1 phase and by loss of synchronized division. ESCRTs are expressed prior to MBT due to maternal expression. Moreover, we detected ESCRT candidates localize to the midbody in stages prior to MBT, where abscission is inhibited. It therefore appears that the abscission machinery is present, however abscission is still inhibited. Study this unique abscission inhibition will shed light on ESCRT regulation processes, and will contribute to understand ESCRT machinery during development.
