PT  - JOURNAL ARTICLE
AU  - Shai Adar-Levor
AU  - Dikla Nachmias
AU  - Shani T. Gal-Oz
AU  - Yarden M. Jahn
AU  - Nadine Peyrieras
AU  - Assaf Zaritsky
AU  - Ramon Y. Birnbaum
AU  - Natalie Elia
TI  - Cytokinetic abscission is part of the mid-blastula transition switch in early zebrafish embryogenesis
AID  - 10.1101/2020.07.26.221515
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.07.26.221515
4099  - http://biorxiv.org/content/early/2020/07/26/2020.07.26.221515.short
4100  - http://biorxiv.org/content/early/2020/07/26/2020.07.26.221515.full
AB  - Animal cytokinesis ends with the formation of a thin intercellular membrane bridge connecting the two newly formed sibling cells that is ultimately resolved by abscission. While mitosis is completed within 15 minutes, the intercellular bridge can persist for hours, maintaining a physical connection between sibling cells and allowing exchange of cytosolic components. Although cell-cell communication is fundamental for development, the potential role of intercellular bridges during embryogenesis have not been fully elucidated. Here, we found that in early zebrafish (Danio rerio) embryogenesis, abscission is delayed and cells do not resolve their intercellular bridges until midblastula transition (MBT), giving rise to the formation of small inter-connected cell clusters. Interestingly, abscission commences during the MBT switch, which is manifested by cell cycle elongation, loss of synchronized divisions and genome activation. Moreover, depletion of Chmp4bb which is an essential ESCRT-III component for scission, delayed abscission beyond the MBT switch. Hallmark features of MBT, including transcription onset and cell shape changes, were similar in sibling cells connected by intercellular bridges, proposing a role for intercellular bridges in maintaining cell-cell communication in the embryo. Taken together, our data suggest that abscission is part of the cellular changes that occur during MBT and that cells coordinate their behavior during this critical embryonic phase through persisted intercellular bridges.Significance Statement In this work we show that the last step of cytokinesis, termed abscission, is inhibited in early zebrafish embryos. As a result, sibling cells remain connected to one another for several cycles and mutually time their developmental progress including transcription onset. Abscission commences at the 10th cell cycle, when embryos enter the midblastula transition (MBT) switch in which embryonic cells become individualized and exhibit the characteristics of mature cells. Our data suggest that abscission is part of the MBT switch and that embryonic sibling cells mutually time their developmental progress by maintaining physical connections between them in the early embryo.Competing Interest StatementThe authors have declared no competing interest.