Every life begins with a single cell. This divides again and again until a complete organism is formed. But how exactly this fundamental process takes place in some animals has been a mystery until now. Researchers at the Technical University of Dresden have now discovered a surprising mechanism that fundamentally changes our understanding of cell division.
The discovery concerns animals with particularly large egg cells. Sharks, birds, reptiles and zebrafish, a type of fish, are among them. The cells in their embryos are huge and full of yolk. This yolk serves as a food supply. However, it is precisely this that makes cell division complicated.
A mechanism like a ratchet
The inside of the cell, the cytoplasm, changes its consistency rhythmically. In certain phases, it becomes solid and provides support for the actin ring. In other phases, it becomes liquid. The ring can then constrict more deeply. This change is repeated over several cell cycles. The ring contracts bit by bit. "The temporal ratchet mechanism fundamentally changes our understanding of cytokinesis," emphasizes Jan Brugués, head of the study.
"Zebrafish are a fascinating special case, as cytoplasmic division in their embryonic cells is inherently unstable," explains Alison Kickuth. The cells divide particularly quickly in order to overcome this instability. The division takes place over several cell cycles by alternating between stability and liquefaction. The discovery could apply to many egg-laying species. It shows how adaptable nature is. For science, this opens up new perspectives for research into biological processes.
