Month: January 2014

Cell Image of the Week – Mitotic Catastrophe

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Here is one of the images that we took using a Leica SP8 confocal microscope this week in the lab.
It is a 3D image of a HeLa cell that has completely stuffed up mitosis (undergone mitotic catastrophe). It has separated whole chromosomes randomly into 2 daughter cells instead of separating the two identical chromatids in two.

And here is an artistic version just for fun !

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A brief Intro to Greatwall Kinase…The King of Mitosis

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Our favourite protein in the lab is Greatwall kinase. It was first discovered in 2004 to be critical for cell division in fruit flies (1,2) . The trail then went cold for a few years as to its exact function, but in 2009, while I was working as a post-doc in France, I was fortunate enough to be in the lab that uncovered its exciting mode of action. For cells to get into mitosis they must activate a key protein called cyclin dependent kinase 1 (Cdk1). I like to think of this as the accelerator in a car. So to get moving cells push on the gas!
And conversely to get out of mitosis you need to hit the brakes. These brakes are the phosphatases which reverse the action of kinases like Cdk1. That’s great but what is missing from this equation?
Well like any car it’s pretty useless without a driver to co-ordinate the accelerator and brakes. And this is where Greatwall (Gwl for short) comes in. It makes sure that when Cdk1 (accelerator) turns on that the breaks get turned off and vice versa (3,4). Without Gwl the cell gets into a lot of trouble very fast, which you can see in the image below. Here I depleted the human version of Gwl (a gene called MASTL) and watched what happened as cells tried to undergo mitosis (5). As you can see they don’t do a very good job… the result is cells fail to divide correctly, resulting in multiple defects and often cell death.

Gwl Figure

I hope you enjoyed part one of my feature on Gwl, and in part 2 I will into more details about this amazing and exciting new protein.

References:

1. Bettencourt-Dias, M. et al. Genome-wide survey of protein kinases required for cell cycle progression. Nature 432, 980–987 (2004).

2. Yu, J. et al. Greatwall kinase: a nuclear protein required for proper chromosome condensation and mitotic progression in Drosophila. J Cell Biol 164, 487–492 (2004). [Link]

3. Vigneron, S. et al. Greatwall maintains mitosis through regulation of PP2A. EMBO J 28, 2786–2793 (2009). [Link]

4. Lorca, T. et al. Constant regulation of both the MPF amplification loop and the Greatwall-PP2A pathway is required for metaphase II arrest and correct entry into the first embryonic cell cycle. J Cell Sci 123, 2281–2291 (2010). [Link]

5. Burgess, A. et al. Loss of human Greatwall results in G2 arrest and multiple mitotic defects due to deregulation of the cyclin B-Cdc2/PP2A balance. Proc Natl Acad Sci USA 107, 12564–12569 (2010). [Link]

Icy: More Excellent free Microscopy software !

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Science Tech Blog

ICY is some great free software that goes extends beyond image J and provides some more advanced tools and a nicer GUI.

There are also a heap of cool plugins available including a new one called Active cell, which makes it quick and easy to outline a cell in either 2D or 3D !  There is also a nice review of this plugin here.

ICY

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