Wednesday, November 27, 2013

Scientists now able to observe molecular motor movement during cell division

The molecular motor Xkid is well characterized for its critical role in aligning chromosomes during cell division. This has been determined based on results obtained from in vitro experiments using purified Xkid, which showed directed movement of this protein on microtubules. However, until now scientists had not been able to observe Xkid behavior on intact spindles.

Diagram of a mitotic spindle

During cell division chromosomes must be precisely segregated so that they can be divided between the two daughter cells. If this segregation is not performed correctly this can result in severe illness or malignant tumor transformation. The spindle apparatus is composed of numerous microtubules and is required for cell division. Xkid molecules are located in the spindle apparatus so a collaboration of scientists from Asia sought to characterize the movement of Xkid in its native environment. The results of their collaboration are published in an article entitled: 'Chromosome position at the spindle equator is regulated by chromokinesin and a bipolar microtubule array'.

In this article, the authors describe the binding of up to four Xkid molecules to a quantum dot (Qdot) and monitored the movement of the Qdot on the microtubules of the meiotic spindle of Xenopus egg extracts. The Xkid-Qdots were able to travel on average 5 micrometers and up to 17 micrometers, which is quite far by cell size standards. They were able to move these relatively long distances by changing which microtubule track they used, always moving along the microtubule with a defined polarity, until they accumulated around the metaphase plate.

These results will contribute to our understanding of how chromosome segregation occurs and thus what goes wrong when chromosomes are incorrectly segregated leading to medical disorders.

Some information for this blog was obtained from the Science Daily article: Molecular Motors' Involved in Chromosome Transport Observed