In some of my experimental test group samples i am observing high G2-M phase cells. Does that indicate that most of the cells are able to go through the g0/gi and s phase successfully and there is less hinderance in the cell cycle process. ?
Not necessarily. It could also result from cell cycle arrest or delay at G2/M. Without knowing if your samples are synchronous in cell division and how you observe the cell cycle phases, it is hard to tell what is going on. In an asynchronous system, a high percentage (higher than usual) of G2/M cells may actually mean that the cells take long time to go through G2/M or are arrested at G2/M. G2/M transition and M phase are typically short phases of the cell cycle. So normally you don't see G2/M cells as often as cells of other phases, unless if you have a synchronous system and you happened to observe the cells while most of them are going through G2/M.
Not necessarily. It could also result from cell cycle arrest or delay at G2/M. Without knowing if your samples are synchronous in cell division and how you observe the cell cycle phases, it is hard to tell what is going on. In an asynchronous system, a high percentage (higher than usual) of G2/M cells may actually mean that the cells take long time to go through G2/M or are arrested at G2/M. G2/M transition and M phase are typically short phases of the cell cycle. So normally you don't see G2/M cells as often as cells of other phases, unless if you have a synchronous system and you happened to observe the cells while most of them are going through G2/M.
I agree with Ming - delay or arrest. It is hard to tell what it is without looking at the cell cycle distribution and without knowing more about your samples.
- How high is the G2/M % you observe?
- Are you treating your test samples with something?
I assume you have not synchronised your cells. You might want to do that to get a clearer picture. Then you would know for sure the differences between your samples. You can try thymidine synchronisation for example.
After that you might want to do a mitotic index analysis (e.g. using phospho-histone H3 antibody) to distinguish between a G2 and a mitosis delay/arrest.
Dear Mr. Ming Yang and Miss. Constantia Pantelidou,
Thanks for your comments and suggestions. I am doing cell cycle analysis in mice femur bone marrow cells following chronic in vivo exposure of my experimental test substances in swiss albino mice test system. In some of the test group samples i am observing 65-80% G2-M phase cells.
The % is quite high, suggesting arrest. I have never worked with bone marrow cells but generally a G2/M arrest usually means that your test substance either causes DNA damage thereby activating the G2/M checkpoint and preventing cells from entering mitosis (arrest in G2 phase) OR it is a mitotic inhibitor i.e. interferes with the process of mitosis and arrests cells in mitosis (likely metaphase arrest with activation of the spindle assembly checkpoint) .
I am not sure what your aims are, but if I wanted to understand the effects of the test substance I would:
(1) synchronise cells using thymidine, to draw definite conclusions about the arrest
(2) perform mitotic index analysis to distinguish between G2 or mitotic arrest
(3) If it's a G2 arrest I would look for the presence of DNA damage. If it's a mitotic arrest I would do immunofluoresence microscopy or live cell imaging to observe the cells and determine the stage in which cells arrest (could be before spindle assembly, could be before cytokinesis).
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