Why the thumb of the right hand is on the left...( This press release is available in ...)

This press release is available in German.

It is the concentration of a few signaling molecules that determines the fate of individual cells during the early development of organisms. In the renowned journal Current Biology, a team of molecular biologists led by Pia Aanstad of the University of Innsbruck reports that a variety of molecular mechanisms accounts for the interpretation of the concentration of the signaling molecule Hedgehog.

The development of an organism is a complex process to which a dozen or hundreds of signaling molecules contribute. Some of these molecules have dozens of functions in the fruit fly and in humans alike. One of these molecules Hedgehog controls the development of, for example, the extremities, the central nervous system, the teeth, eyes, hair, lung and the gastrointestinal tract. "What is most remarkable: The cells are told what to do not only because the molecule is present but also by the different concentrations of the molecules in the tissue", says group leader Pia Aanstad of the Institute for Molecular Biology of the University of Innsbruck. "The concentration of Hedgehog makes the thumb of the right hand grow on the left hand side and the thumb of the left hand grow on the right hand side." Thus, scientists define Hedgehog as a morphogen a signal that is concentration-dependent and controls the pattern formation of an organism. A mutation in this signaling pathway induces dramatic and embryonically lethal malformations in the early developmental stage such as the formation of just one central eye. Defects in the Hedgehog signaling pathway in humans are a cause for one of the most common birth defects holoprosencephaly. "Hedgehog genes are not new in evolution and the signaling pathway functions in the fly, mouse, fish and in humans similarly", says Pia Aanstad. In her research work she focuses on the ze
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