mitotic cleavage furrow ingression

Definition

Target type: biologicalprocess

Advancement of the mitotic cleavage furrow from the outside of the cell inward towards the center of the cell. The cleavage furrow acts as a 'purse string' which draws tight to separate daughter cells during mitotic cytokinesis and partition the cytoplasm between the two daughter cells. The furrow ingresses until a cytoplasmic bridge is formed. [GOC:kmv, PMID:12707312]

Mitotic cleavage furrow ingression is the final stage of cytokinesis, the process that divides the cytoplasm of a parent cell into two daughter cells after mitosis. It's a complex and tightly regulated process driven by a coordinated interplay of cytoskeletal components, motor proteins, and signaling pathways. Here's a detailed description:

1. **Formation of the Cleavage Furrow:**
- The cleavage furrow begins as a shallow groove on the cell surface, usually at the equator of the cell where the mitotic spindle poles are positioned.
- This initial furrow formation is driven by the contraction of the actin-myosin ring, a band of microfilaments made of the proteins actin and myosin.
- The actin-myosin ring is assembled beneath the cell membrane at the future cleavage furrow site.
- Myosin II, a motor protein, interacts with actin filaments, causing them to slide past each other, generating contractile force.

2. **Ingression of the Cleavage Furrow:**
- As the actin-myosin ring contracts, it pulls the cell membrane inwards, deepening the cleavage furrow.
- This process of ingression is highly regulated, with several factors influencing its rate and direction.
- Microtubule depolymerization at the midzone of the spindle, where the spindle poles are located, provides space for the cleavage furrow to ingress.
- The cell cortex, a specialized region of the cell membrane, also contributes to the stability and directionality of the furrow.

3. **Final Separation:**
- As the cleavage furrow continues to ingress, it eventually meets in the middle of the cell, forming a narrow bridge called the midbody.
- The midbody contains remnants of the mitotic spindle and is ultimately severed, leading to the complete separation of the two daughter cells.
- This final step involves the coordinated action of several enzymes and proteins that remodel the cell membrane and cytoskeleton.

4. **Regulation of Cleavage Furrow Ingression:**
- The process of cleavage furrow ingression is tightly controlled by a complex network of signaling pathways.
- These pathways involve signaling molecules like Rho GTPases, which regulate the assembly and contraction of the actin-myosin ring.
- Other factors, including cell size, shape, and the availability of nutrients, also influence the efficiency of cleavage furrow ingression.

In summary, mitotic cleavage furrow ingression is a complex and dynamic process that requires the coordinated action of many cellular components. It's essential for proper cell division and the development of multicellular organisms.'
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