Saturday, May 19, 2012

The principles of cellular movement

Cells are the basic building blocks of life. They come in many different forms or shapes, and perform a wide variety of functions. During the embryonic stage of development, cells rearrange, move, multiply and die, showing that our body is not simply a static collection of individually arranged cells. Cells can move, and some types spend their whole life travelling through the body. Signalling mechanisms are necessary to direct cellular movement, and the same is necessary for tissue growth: cells need to know in which direction they should grow so that the tissue forms its correct shape. A collaboration of scientists from Lehigh University and the University of Miami elucidated a basic mechanism that makes cells move, thereby uncovering one of the foundations of 'organised life'.

Not every part of the cell is the same: one end can have different properties, such as differences in protein presence or a difference in structure. It means that one part of the cell can behave in a different way than other parts. This is called cell polarity, and it was already known to play an important role in cellular movement. It helps make our body asymmetric during development: from head to feet, from back to belly and from left to right. It even plays a role during the very first steps of creating new life: a fertilized egg accumulates certain proteins at one end, which causes them to end up in just one cell after the first cell division, immediately creating asymmetry.
A fertilised egg. The point of entry of the sperm cell immediately results in asymmetry, because of differences in protein accumulation (PAR3- vs. PAR2-). Eventually, during division, two different cells will arise. (source)
In their study, scientists from Lehigh University and the University of Miami found that a protein known as Cdc42 plays an important role in cell polarity and movement. Presence of Cdc42 resulted in oscillations that affect the growth and the morphology of the cell. By using yeast, that function as single cells but can also learn to cooperate, the scientists showed that presence of Cdc42 and the molecules it interacts with forms a basic mechanism used by cells to control their shape and form. They think that Cdc42 starts it all off : according to them, the 'ballet' for cell polarity is induced by this protein. And not just in yeast, as it is likely all organised forms of life will use a similar mechanism.
Presence of Cdc42 makes the yeast cell grow in a certain direction.
By discovering ways of cellular movement and growth, we gain information about one of the most basic and important features of life. Without proper arrangement, our complexly organised bodies cannot exist in the way they do. Additionally, if we want to create our own tissues in the lab, it is good to know how we can influence growth and morphology, to create better tissues for implantation Although it would likely take years before anyone could make good practical use of the present study, it still is important to keep uncovering new principles of life. 

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