Syntelic
Syntelic attachment occurs when both sister
Normal cell division distributes the genome equally between two daughter cells, with each chromosome attaching to an ovoid structure called the spindle. During the division process, errors commonly occur in attaching the chromosomes to the spindle, estimated to affect 86 to 90 percent of chromosomes.[3]
Such attachment errors are common during the early stages of spindle formation, but they are mostly corrected before the start of anaphase.[4] Successful cell division requires identification and correction of any dangerous errors before the cell splits in two.[3] If the syntelic attachment continues, it causes both sister chromatids to be segregated to a single daughter cell.[5]
Causes
Microtubules extend from the spindle poles and attach to the first kinetochore they encounter.[6] Because this process is stochastic and not facilitated or directed, the first microtubules to come into contact with a kinetochore may not have originated at the correct spindle pole.[7] Normally, the sister kinetochores are on opposing sides of the chromosomes, facing outward toward their respective spindle poles.[8] This arrangement enhances the likelihood of properly bi-oriented chromosomes and is sometimes referred to as a mechanism for 'avoidance' of syntelic attachment.[8][9] However, sometimes the kinetochores are found on the same side of the centromere, and this error cannot be corrected stochastically.[8] Instead, the spindle must actively exert forces on one of the two kinetochores to relocate it to the proper, outer edge of the centromere.[8] If the geometry and orientation of the two kinetochores is not corrected, the cells can still effectively achieve bi-orientation through the employment of error correction mechanisms.[9]
Error Correction
Error correction is closely tied to the
Robust destabilization by Ipl1/Aurora B in the absence of tension leads to a specific challenge: the initial establishment of bi-orientation, prior to the buildup of tension, would be sensitive to Ipl1/Aurora B activity.[13] This is referred to as the initiation problem of biorientation (IPBO), and is resolved by implementing a delay between sensing the tension and destabilizing the attachment.[13] Modeling has indicated that such a delay could be introduced if the rate of Ipl1/Aurora B kinase activity is slower than that of the counteracting phosphatase activity at the kinetochore.[13] The time delay allows for tension to be established at bi-oriented chromosomes, so that only syntelic attachments are phosphorylated and destabilized.[13]
Consequences
Syntelic attachment is not uncommon in early
See also
References
- ^ "Examining chromosome-microtubule attachment". Archived from the original on 3 September 2010.
- PMID 25303117.
- ^ a b "Molecular forces are key to proper cell division". www.sciencedaily.com. University of Massachusetts Amherst. January 21, 2013. Retrieved 3 February 2017.
- ^ "CELLS Interactive Glossary: Syntelic attachment". bioscience.jbpub.com. Jones and Bartlett Publishers. Retrieved 3 February 2017.
- PMID 20068571.
- ^ S2CID 30090031.
- ^ PMID 32760074.
- ^ PMID 18046416.
- ^ S2CID 4418232.
- ^ S2CID 4421746.
- ^ PMID 20885417.
- ^ PMID 21106376.
- ^ PMID 28601560.
- ^ PMID 28067761.
- ^ PMID 21997207.