Penn scientists discover cells reorganize shape to fit the...( PHILADELPHIA - Flip open any biology...)

PHILADELPHIA - Flip open any biology textbook and you're bound to see a complicated diagram of the inner workings of a cell, with its internal scaffolding, the cytoskeleton, and how it maintains a cell's shape. Yet the fundamental question remains, which came first: the shape, or the skeleton?

Now a research team led by Phong Tran, PhD, Assistant Professor of Cell and Developmental Biology at the University of Pennsylvania School of Medicine, has the answer: Both.

The findings, published online this week in the journal Current Biology by co-senior authors Tran and Matthieu Piel of the Institut Curie, Paris, combine genetics, live-cell imaging, and microfluidics technology. They were able to force normally rod-shaped yeast cells to grow within tiny curved channels. Using the channels, they made rod-shaped cells deform into curved-shaped mutant cells and conversely, curved-shaped cells straighten out into a rod. The surprising finding: as the cells bend, they reorganize their cytoskeleton, and as they reorganize their internal skeletons, the cells further adjust their shape.

Cell shape gone awry has been implicated in some forms of cancer. In the future, one potential implication of Tran's findings is that it might be possible to rescue certain disease states via squeezing or otherwise applying mechanical pressure to tissues or organs. But that, he concedes, is "completely science fiction on my part." Instead, he says at this point this study is pure, basic research. "It was just a cool experiment."

The findings point to a type of feedback loop. "The cytoskeleton changes the shape of the cell and the shape of the cell also changes the organization of the cytoskeleton," he says. "In fact they feed back on each other, so any perturbation on one system will change the other, and visa versa."

The results validate a common belief among cell biologists, says Tran that to cause a cell to form a branching projection, such as filop
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