Literature

"Mitosis and meiosis are the most exciting and elaborate processes that occur during the life of dividing cells. Over the course of little more than an hour (for mitosis), macromolecular structures throughout the cell are reorganized, signalling pathways are activated and silenced, proteins are degraded and, at the end of each division, two daughter cells are born. Not only are mitosis and meiosis wonderfully elaborate, it is also essential that they proceed without error, as mistakes can result in the death of the organism."

The authors of a significant review article ask: "How are all of these processes coordinated?" and go on to review the knowledge that has emerged to date. In particular, they focus attention on chromosomal passenger proteins. Previous suspicions that these passenger proteins "might regulate key mitotic processes by moving from place to place in the dividing cell" have been confirmed "and studies of these proteins comprise a major area of ongoing mitosis and meiosis research." What emerges is a fascinating picture of coordinated activity, with events "orchestrated with a precision that is worthy of a classical symphony, with different activities being switched on and off at precise times and locations throughout the cell." In this musical analogy, the chromosomal passenger complex (CPC) is the conductor.

"We now understand that the CPC orchestrates mitosis and meiosis at several different levels to ensure that two daughter cells are generated with an accurate distribution of genetic material. The regulation of kinetochore-microtubule attachments in a bipolar spindle, the delay of anaphase onset when spindle tension is aberrant, the regulation of sister chromatid cohesion and the completion of cytokinesis are among the crucial mitotic functions that require CPC activity."

The authors conclude by utilising the analogy again: "The score for the elaborate and wonderful symphonies that are mitosis and meiosis therefore remains unfinished, with much more to be written." This comment is worthy of further thought. An unfinished symphony implies that the composer ended the work prematurely. However, we would not be here if mitosis and meiosis were not working smoothly during our personal experience of life. The symphony IS already written, but we have not yet fully read the score. We have heard the music in part - much more awaits us! The control systems within cells evoke aesthetic feelings akin to hearing a skilled orchestra led by a gifted and inspirational conductor. The important point is that the awe and wonder is our response to what we find in the natural world. We discover a score (we do not write it) and the more we discover, the more we put the music back into our mechanistic models of the world. Contrast this with the much-quoted words of Richard Dawkins:

"The universe we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind, pitiless indifference. As that unhappy poet A.E. Housman put it: 'For Nature, heartless, witless Nature Will neither care nor know.' DNA neither cares nor knows. DNA just is. And we dance to its music."
(Dawkins R., "River out of Eden: A Darwinian View of Life," Phoenix: London, 1996, p.155.)

We are not dancing to music that is heartless and witless! We are dancing to music that has a depth of meaning we are only beginning to grasp.

Chromosomal passengers: conducting cell division
Sandrine Ruchaud, Mar Carmena and William C. Earnshaw
Nature Reviews Molecular Cell Biology, 8, 798-812 (October 2007) | doi:10.1038/nrm2257

Abstract: Mitosis and meiosis are remarkable processes during which cells undergo profound changes in their structure and physiology. These events are orchestrated with a precision that is worthy of a classical symphony, with different activities being switched on and off at precise times and locations throughout the cell. One essential 'conductor' of this symphony is the chromosomal passenger complex (CPC), which comprises Aurora-B protein kinase, the inner centromere protein INCENP, survivin and borealin (also known as Dasra-B ). Studies of the CPC are providing insights into its functions, which range from chromosome-microtubule interactions to sister chromatid cohesion to cytokinesis, and constitute one of the most dynamic areas of ongoing mitosis and meiosis research.

Quote:
"Perhaps the problem is that for some scientists reductionism functions as a security blanket. It avoids the need to ask too many questions, to stare into the abyss of fundamental uncertainty. If we abandoned the universality of the reductionist approach, who knows what would happen? For sure, the nature of biological science would change. But so it should!"
Denis Noble, The Music of Life: Biology beyond the Genome. Oxford UP, 2006, p. 66.