The modeling and simulation of self-organized intracellular twisters in the Drosophila oocyte

Cytoplasmic streaming is the mass movement of cytoplasm (ie the gelatinous fluid inside cells) within a living cell. This flux, which is known to regulate various intracellular processes, can vary greatly between different cell types at different stages of cell development. Examining and modeling different types of cytoplasmic fluxes can help us understand how they arise in specific cell types.

Past studies have primarily examined cytoplasmic fluid streaming in large cells where it is often argued that diffusion is too slow to enable the biological processes that organisms need to perform (e.g., eggs or embryonic development, or in larger plant cells).

As a result of this slow diffusion, flow enables rapid distribution of cellular components. In early fly oocytes (i.e., developing egg cells), for example, cytoplasmic streaming appears disorganized, whereas in later stages of development, where oocyte Larger, they may appear massive and circular.

Flatiron Institute researchers, building on previous work, recently introduced a versatile modeling strategy to study self-organized cytoplasmic streaming in systems consisting of hydrodynamically coupled disordered fibers. can be done

This model, introduced I Nature Physics And in collaboration with scientists from Princeton and Northwestern universities, insights into self-organized cytoplasmic flow were gathered in combination with data collected in experiments on the Drosophila (i.e., fruit fly) oocyte.

“I have been working for some time in the general areas of biologically active matter, intracellular mechanics, and complex fluids,” paper co-author Michael J. Shelley told Phys.org. “The problem addressed in our recent paper combines all these areas, each of which I really like.

“I learned about this particular flow problem in oocytes from my friend Ray Goldstein and realized that earlier work with my Flatiron colleague David Stein could be adapted to understand something about the oocyte problem. It happened, and I worked closely with David and Ray, their colleagues at Cambridge First, strip the 2D model down to the very bottomThis work was published in 1947. Physical examination letters In 2021

Flatiron Institute researchers previously developed a variety of tools to study the hydrodynamics of moving microtubules, the rigid biopolymers that are central to the cell’s cytoskeleton. Shelley, Stein and their colleagues Reza Farhadifer, Sayantan Dutta, and Stas Shvartsman plan to use these numerical tools to study the initiation of self-organized cytoplasmic flow in 3D cells.

“The primary goal of our recent study was to provide a minimal, but not too reduced, model that includes only microtubules, molecular motors, and cytoplasm that can explain experimental observations and make predictions,” Shelley explained. I can help,” explained Shelly.

Recent research by Shelley and his colleagues has combined physics and mathematical theories with experimental results. The researchers began by creating a model that they could then use to simulate self-regulated cytoplasmic streaming in the Drosophila oocyte.

“We wrote one Mathematical model for the stresses that molecular motors create by moving the microtubule,” said Shelley. “This model must allow the microtubule to bend under load, and to move the cytoplasm to bend it. Affects the bending of other microtubules. Next, he used a high-quality piece of software—here called SkellySim—that lets you simulate a few thousand such microtubules that collectively push and interact with a bending fluid. “

After developing their model and running simulations, Shelley and his colleagues conducted experiments on Drosophila oocytes. First, they used Light microscopy analyzed the collected data using particle imaging velocimetry to assess cytoplasmic motions in developing egg cells and then reconstruct cytoplasmic velocity fields.

“Our paper provides a clear example of how, with very few components, a large-scale transport system (i.e., streaming flow) can emerge from the interaction of only a few components (i.e., microtubules, motors, and cytoplasm) in a cell,” said Shelley. “The beauty lies in its robustness, as it governs the model over large parts of parameter space. Wants to make a twister. It’s a perfect example, I think, of biological self-organization to perform a task.”

Specifically, using their model, the researchers were also able to predict the effect of cell shape on the orientation of the twisters. Their predictions show that although the dynamics of cytoplasmic streaming in Drosophila oocytes can be incredibly complex, they ultimately result in a simple final state (i.e., a twister).

The findings gathered by Shelley and his colleagues may soon pave the way for further exploration of cytoplasmic streaming, particularly focusing on this simple twister state. This can lead to exciting new discoveries about the physics underlying important processes in biological cells.

“This work demonstrated that power. High performance computing And advanced algorithms can help understand biophysical phenomena,” added Shelley. “In our next research, we plan to explore how these twisters mix components in the cell or from one point to another. Enable their delivery to other locations.

“There are other transport systems within the oocyte, such as through ring ducts, which are very interesting. I’m generally interested in the manifold ways that the cellular cytoskeleton organizes itself to do cellular things. does.”

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