Question

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2. A set of experiments was performed by Nie et al. to test the effect of actin drugs on cell motility. For this assay, the author:s used the following protocol, with data shown in the figure to the2hr right 1. Grow cells in a chamber to a full monolayer 2. Removed the cells from the chamber surface on the right side of the dashed lines. 3. Allow remaining cells to migrate via actin-based cell motility for up to 24hrs. This protocol was performed for cells incubated with plain media, media phalloidin, or media + cytochalasin. 4 hr 8 hr A. (4pts) The two columns in the Figure, A & B, are representative 24 hr of the results observed for these three conditions. Please describe the differences between A & B, including an evaluation of how much cell motility there is in these results. Figure A (FYl, these images are easier to see on the original digital file.) B. (4pts) For cells exposed to plain media, do you believe the results were more like ColumnA or B? Please provide your reasoning. C. (4pts) For cells exposed to cytochalasin, do you believe the results were more like Column A or B? Please provide your reasoning. D. (4pts) For cells exposed to phalloidin, do you believe the results were more like Column A or B? Please provide your reasoning.

Answer 1

A. The cells have been removed from the right side in both column A and column B. However, two hours after removal a few calls are seen beyond the border in column A which is absent in column B. At 4 hours, cells can be observed to have migrated around 10% towards the right side only in column A. At 8 hours cells reach upto 30% in column A while there is no movement in column B. Finally at 24 hours, cells show migration till 80%in case of column A, but no migration is observed in column B. Thus, we can say that the migration of cells happened only in column A.

B. In presence of plain media, since there is absence of any actin binding proteins, the cells will not move towards the right side and thus the results would look like column B.

C. Cytochalasin is a molecule which binds to the barbed ends of the actin filament. It tends to inhibit the dissociation as well as the association of the actin subunits at that particular end.

D. Phalloidin has been observed to react in a stoichiometric manner with actin. It tends to enhance the actin polymerization rate and also stabilizes the structure of F-actin. Thus in this case, the results would look like column A.