My Research Question
Sorry for the late update. I keep getting halfway through blog entries on the day they’re due and then completely abandoning them. I’m not really sure how to phrase my research question. I know what I’m doing, and what I’m looking for, but I feel like putting my research question into words without describing the method I’m using to answer it makes it seem completely trivial. My question is very simple: How strongly do mitotic density and axis contribute to shape change in the imaginal disks throughout caterpillar development? Compared to what I’ve read other people are doing, it seems like a walk in the park.
I had to come up with the method to quantify shape change. This involved a lot of reading – pure math papers, biology papers, long MATLAB pages – a huge amount and variety of information. “Shape” is one of those words (like “Trinity Requirements”) that people use all of the time without really understanding what they’re talking about. Mathematically, it’s defined as “all the geometric information that remains when location, scale, and rotational effects are filtered out from an object”. That means in order to rigorously compare shape at different stages of wing development, many steps have to be taken to filter that non-essential information out so all you’re left with is shape (translating the sets of points being compared so their centroids overlap, rescaling them so they have the same centroid size, and rotating them to minimize distance between homologous points).
After that process (called the Procrustes superimposition, after the ancient Greek monster who used to use torturous methods to make all travelers he encountered fit his bed), a thin plate spline is created to show the deformation necessary to achieve the biological changes between wings at different stages of development. By looking at the spline, it is possible to see where there is the greatest relative size change, and (somewhat more interestingly), the greatest relative shape change.
Now we can come back to my research question. Since we have found a method to quantify shape and size changes between imaginal disks at different stages of development, we can go back to our slides and (somewhat tediously) count mitotic density at different areas of the wing and see how strongly mitotic density correlates with size change. (Non-uniform changes in cell size could also contribute). If there’s enough time after that’s completed, I’m going to go back and re-count the mitoses, this time looking at how mitotic axis correlates with size change. (If the growth in one region of a wing is predominantly in one direction, it stands to reason that most of the mitoses in that region are “pointing” in that direction, but that will probably take more time than I have this summer to prove).
So there’s my project! Any questions (or helpful comments) would be more than welcome.
