Cytokinesis: separation of the cell cytoplasm after nuclear division

Primary mechanisms

Different groups of organisms use distinct mechanical strategies to achieve cytokinesis. The two canonical eukaryotic mechanisms are:

• Contractile ring (animal cells): a band of actin filaments and myosin motors constricts at the cell equator, pinching the membrane inward to form a cleavage furrow and eventually splitting the cell.
• Cell plate formation (plant cells): membrane-bound vesicles derived from the Golgi coalesce at the center of the dividing cell to build a new cell wall and plasma membrane, guided by a microtubule structure called the phragmoplast.

Other microbes and fungi may use variations such as septation, budding or polar growth to achieve cytoplasmic separation.

Timing and regulation

Cytokinesis is coordinated with chromosome segregation so that each daughter cell receives the correct complement of genetic material. Regulatory networks monitor mitotic exit and cytoskeletal remodeling; when these signals permit, machinery for membrane remodeling and abscission completes the split. Errors in timing or regulation can produce binucleate cells, aneuploidy or multinucleation.

Biological importance and examples

Successful cytokinesis is essential for growth, tissue maintenance, embryonic development and asexual reproduction. In animal embryos, rapid early divisions rely on tightly controlled cytokinesis. Failure of cytokinesis is implicated in developmental defects and is often observed in cancer cells, where division control is compromised.

Historical notes and distinctions

Microscopists in the 19th century first described the separation of cytoplasm as distinct from nuclear division, and modern cell biology has since identified the molecular players and steps involved. For more on nuclear division processes that precede cytokinesis, see mitosis and meiosis.

Notable fact: while cytokinesis is a defining feature of eukaryotic cell division, prokaryotes accomplish cell division by related but distinct septation and binary fission mechanisms.