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Friday, August 26, 2011

EMBRYONIC CELLS NARROWLY MISS DESTRUCTION

It's amazing anyone of us were born after reading their amazing survival abilities.  It makes our children all the more precious.

Research based at Princeton University has revealed that newly fertilized cells only narrowly avoid degenerating into fatal chaos. At the same time, scientists have discovered that embryos have acquired a mechanism to contain this dangerous instability, a finding that could help biologists unravel other mysteries about the first hours of life.

A team led by Princeton Professor of Molecular Biology Ned Wingreen reported recently in the journal PLoS Computational Biology that contrary to the idea that embryonic cells develop in natural synchrony, they are prone to descend into disarray. Without stabilization, cells develop on different schedules, and many stop developing altogether, which threatens the embryo's survival.

This lurking state of disorder was revealed through computational models the researchers constructed of the embryo cell cycle. The cell cycle is the repeated division and duplication of cells that transforms a single fertilized egg into a full-grown organism. Scientists already knew that embryonic cell cycles are initiated by a swift wave of calcium that emanates from the fertilization site and prompts the embryo's cells to divide and duplicate -- or oscillate, in biological terms.

A natural assumption among scientists had been that once initiated, the impulse to oscillate would ripple across the embryo -- which begins as one big cell that then divides repeatedly -- and set the stage for multiple rounds of cell division to occur in sync. Wingreen and his colleagues found, however, that the natural spread of oscillation is unstable and would result in an erratic patchwork of missed and incomplete cell divisions. They predicted that cell activity instead has to be triggered throughout the embryo at almost exactly the same time.

The researchers' simulation produced the first indication that the fast-moving calcium wave known to spark cell division doubles as a synchronizer that sets cells to the same developmental timetable. The finding revealed a crucial role for the somewhat puzzling existence of the calcium wave, as well as a new level of sophistication in how embryos function.

"We didn't have to go searching for chaos, it just came right out at us," Wingreen said. "When the dust settled, it became clear that cell-cycle oscillation, while remarkably uniform in the end, does not come by that harmony on its own, especially not in anything as big as an embryo, which is much larger than a typical cell. But then the question became, if there's this potential for chaos, how does the system avoid it? It turns out that the system needs the calcium wave to avoid chaos and that wave is activated surprisingly fast."

The embryo's need for stabilization and the dual role of the calcium wave illuminates the intricacy of developing embryos, as well as the impressive ability of embryos to prevent their own destruction, said James Ferrell, a Stanford University professor of chemical and systems biology. The Princeton researchers based their work on formulas that Ferrell developed from experiments on African clawed frog embryos that describe how embryos divide and replicate in timed cycles during early development.

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