Researchers at The Forsyth Institute have discovered that a family of proteins known for its role in a variety of cellular mechanisms and diseases also plays a key role in asymmetry---the process through which cells "know" which side they are on as they form bodily organs such as the heart and liver.

The research team, led by Michael Levin, PhD, Associate Member of the Staff, also demonstrated for the first time that the protein family, known as "14-3-3," is involved in embryonic pattern formation and that left-right asymmetry begins much earlier than was previously believed--within one hour of fertilization.

In addition, because the 14-3-3 protein family is found in fungi, plants and vertebrates, the study highlights a conservation of signaling mechanisms between very distant organisms (that is, the mechanisms are identical or very similar) and links the functional physiology of the three kingdoms.

Writing in the October 20 issue of Development, the researchers point out that the 14-3-3 protein family has long been known to affect many aspects of cell development in plants and animals. For example, fungi release a compound called fusicoccin, which can control plant cell behavior by interacting with plant 14-3-3 protein targets. In mammals, 14-3-3 plays diverse roles in cell proliferation, differentiation, and death. In humans, it is used to diagnose "Mad Cow" and Creutzfeldt-Jakob diseases, in which single proteins known as prions are believed to act as infectious agents that cause cell function to go awry.

"Clearly, 14-3-3 proteins play an important natural role in the cell cycle process," Levin said. "Our research establishes a new function for this family of proteins. Learning more about how 14-3-3's are used to control tissue pattern will be very important in developing new approaches for understanding and treating human ills such as cancer (a condition in which cells have lost the ability to acquire correct tissue and organ pattern) and prion disease. A wider understanding of how 14-3-3 proteins control cell cycle and other parameters will be crucial in targeting cell proliferation and function in such illnesses."

Kelly McLaughlin, Assistant Professor of Biology at Tufts University, said: "Discovering that 14-3-3 plays a role in asymmetry is very exciting because it leads us to one of the very first steps in left right patterning. It’s remarkable to be able to determine left-right asymmetry at the two cell stage, which is quite a bit earlier than anyone else has been able to demonstrate." In addition, "finding yet another function for the 14-3-3 signaling pathway that is common to fungi, plants, worms, frogs and humans further illustrates that this evolutionarily conserved family must be critically important to the normal function of many life mechanisms."

According to Levin, the findings will, one day, also help explain such conditions as right-left hand preference, mirror-image twins, right versus left brain dominance, and birth defects that cause organs to develop on the wrong side of the body.

In the study, the scientists found that fusicoccin, a compound produced by fungi to attack plant cells, caused frog embryos to develop some of their asymmetrical organs on the "wrong" side. In plant cells, FC complexes with 14-3-3 proteins to activate H+ pumping across the plasma membrane. The researchers found biochemical and molecular-genetic evidence that 14-3-3 family proteins are part of the receptor which interacts with the fusicoccin in frog embryos, and that perturbation of 14-3-3 protein function results in each organ randomly determining its orientation within the body. The subcellular localization of 14-3-3 mRNAs and proteins revealed novel cytoplasmic destinations and a left-right asymmetry at the first cell division. Using gain-of-function and loss-of-function experiments, the researchers determined that 14-3-3E protein is likely to be an endogenous and extremely early aspect of LR patterning.

Jeremy Green, PhD, Assistant Professor of Genetics at Harvard Medical School and the Dana Farber Cancer Institute, said: "This is clearly one of the last bridging pieces to connect left-right asymmetry to fundamental cell polarity…We are getting very close to the wellspring of the process."

The current study was funded by the American Cancer Society, March of Dimes, American Heart Association, and Harcourt Charitable Foundation.

The Forsyth Institute is an independent, nonprofit research organization focused on oral, craniofacial and related biomedical science.

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