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#cleavage furrow

2 public questions tagged with this topic.

amphibian Development-l

The first cleavage furrow in frog embryos typically:

In Xenopus the first cleavage furrow is meridional, oriented along animal-vegetal axis passing through the sperm entry point initially but ultimately bisecting the newly formed gray crescent opposite entry. Equal bisection ensures both daughter blastomeres inherit dorsal determinants such as stabilized beta-catenin and Dishevelled concentrated by cortical rotation. This equal partitioning preserves dorsal potential bilaterally until later interactions restrict organizer activity dorsally. Subsequent cleavage planes alternate but first furrow's alignment with gray crescent is crucial for establishing bilateral symmetry and axial patterning.

Ref: Browder et al., Developmental Biology, Chapter 8: First cleavage meridional bisects gray crescent in Xenopus.

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Cell Division

The key determinant of the plane of cytokinesis in mammalian cells is the position of:

Placement of contractile ring determining cleavage plane is actively specified by mitotic spindle rather than cell geometry alone. During anaphase, after chromatids separate, antiparallel interpolar microtubules overlapping in middle zone are bundled by PRC1 protein and kinesins KIF4 and MKLP1, forming central spindle enriched with chromosome passenger complex including Aurora B kinase and centralspindlin heterotetramer of MKLP1-MgcRacGAP. This platform concentrates Rho guanine nucleotide exchange factor ECT2 at adjacent equatorial cortex, converting inactive RhoA-GDP to active RhoA-GTP in narrow band precisely midway between segregated genomes. Active RhoA stimulates formin mDia1 to nucleate linear actin filaments and ROCK-mediated phosphorylation of myosin regulatory light chain driving myosin II bipolar filament assembly and constriction. Astral microtubules radiating to polar cortex deliver inhibitory signals via MP-GAP suppressing Rac-mediated branched actin and Aurora A mediated inhibition, ensuring furrow ingresses only at equator perpendicular to central spindle, guaranteeing equal genome partitioning between daughters. This circuitry is highly conserved across eukaryotes, integrating growth factor signals, DNA damage surveillance, and developmental cues, and its disruption frequently underlies oncogenesis, providing targets for checkpoint inhibitors and cancer therapeutics.

Ref: D'Avino et al., J Cell Sci 2015, Cytokinesis Positioning. Glotzer, Science 2005, Central Spindle Signals.

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