Central spindle

Central spindle refers to a structure that forms during the late phases of mitosis and cytokinesis in cell division. It plays a crucial role in the separation of daughter cells. The central spindle is composed of microtubules and associated proteins, including motor proteins such as kinesin and cytoplasmic dynein, which help in the elongation and stabilization of the spindle.

Formation and Function

The central spindle formation begins during anaphase, when the chromosomes are segregated to opposite poles of the cell. It is essential for the positioning of the cleavage furrow and the successful completion of cytokinesis. The central spindle is formed by the interdigitation of antiparallel microtubules emanating from the spindle midzone. Proteins such as Aurora B kinase, MKLP1 (a kinesin-like protein), and Prc1 are critical for the central spindle's assembly and function.

Role in Cytokinesis

Cytokinesis is the process that physically divides the cell into two daughter cells. The central spindle is key to this process, providing a scaffold for the recruitment of proteins that constrict the cell membrane to form the cleavage furrow. Among these proteins, RhoA, a small GTPase, plays a pivotal role in contracting the actin-myosin ring at the site of division.

Regulation

The central spindle's assembly and function are tightly regulated by various kinases and phosphatases, including CDK1, PLK1, and Cyclin B, which ensure the correct timing of cytokinesis. Dysregulation of these processes can lead to cytokinesis failure, resulting in multinucleated cells, a hallmark of certain cancers.

Clinical Significance

Abnormalities in the central spindle can lead to diseases such as cancer, where the regulation of cell division is compromised. Understanding the mechanisms of central spindle formation and function can provide insights into novel cancer therapies targeting cell division.