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Hi Cole. Very interesting talk and I really enjoyed. Here are my questions:
How is the polarization region size controlled in your model? It seems right now small polarized region oscillates and large polarized region can move constantly.
Your current model is applied to study cell migration. Do you assume cell volume conservation in the model? Is it possible to study immobile cells which don’t move but just make project?
1. The region size is going to depend on the values of b and delta (assuming other parameters are fixed). In the oscillatory regime, the b parameter was smaller, so we expect less Rac to be active, and so there is a smaller overall size.
2. Rac will dilute and concentrate as the domain size changes (at least the model, not sure what happens in real cells on this timescale). This is essentially why there is the relaxation-polarization oscillation: in this case there is not enough Rac to maintain polarity when the domain gets bigger, so the polarization is lost. After the domain shrinks, the total average amount is sufficient to support polarity. So yes, I assumed that the amount of stuff is constant.
3. Probably! I don’t know what would happen if we fix the cells but let the edges expand… in the 2d continuum mechanics model, I don’t think we would get big protrusions since the linear viscoelastic physics isn’t the best description for large deformations… other models, e.g., Neo-Hookian might be needed.
Dr. Hao, great talk! I have a question about the mutant conditions. In the double over expression case, do you observe significant cell shape change?
yes, mode 3 cells also generate elongated daughters. but we did not observe much difference in the shape of mother cells. Mother cells become larger during aging in all modes.
Dr. Hao, Thanks for your great talk. I am also interested in agin in yeast cell. I would like to ask if mating also includes in the process, how can we define aging after mating? Will mating create other modes?
What we studied is the aging of haploid cells, which did not mate during the aging process. but it has been found before that the mating capacity is dramatically decreased in aged cells.
Thank you, Nan! Will follow up with you later.
Thank you, Dr. Hao.
Nice talk Kevin!
Kevin, great talk! I know from experience those type of coupled models can be very tricky. Have you had a chance to vary any of the biochemical parameters that affect polarization site size or dynamics and see how the bud shape changes in response?
@Michael It is a great question. I have yet to vary parameter values influencing the polarization site size, but have change the threshold value for choosing location to insert new materials. While I think this is somewhat analogous to changing the polarization site size, but I believe changing the polarization site size will be more biological.
Thank you! Yes, that makes sense. Will be interesting to see how the mechanical coupling interacts with the polarization dynamics
Michael, that is a great question. Right now the cell shape change is not affected by polarized signal yet. We expect to deal with some challenge when two submodes are really coupled. It is also related to how fast polarization can be establish compared with cell growth.
Ah, I see, thank you Weitao. Yeah, it is a tricky problem! Curious to see how it works out
Thank you everybody! Great talks!
Thanks for the great talks!