Biologists at the University of California, San Diego have observed, for the first time, a protein gradient in developing fruit fly embryos believed to trigger the division of the embryo into nervous system and different types of epidermis within complex organisms like humans.
In a paper featured on the cover of this months issue of the journal Developmental Cell, the scientists demonstrate visually and in experimental detail the molecular process by which an embryo begins partitioning itself for subsequent development into neural and distinct forms of epidermal tissue.
Their experiments provide final confirmation of an elegant hypothesis proposed during the 1950s by the mathematician Alan Turing, who suggested that chemicals generated incrementally during the development of a complex organism might cause the differentiation of cells during early embryonic development.
We are now one step closer to understanding the mechanism by which crude spatial information provided by the egg is converted into more refined information that ultimately defines every position along the body axis in exquisite detail, says Ethan Bier, a professor of biology at UCSD who headed the research. This process assures that fingernails grow only on the tips of fingers and two eyes become positioned symmetrically on either side of the nose.
Turing suggested that the chemicals responsible for the developmental changes in the embryo, which he dubbed morphogens, were produced and secreted by one group of cells, then diffused into neighboring cells where they were destroyed a certain rate.
According to Turing, the juxtaposition of cells producing the morphogen with adjacent cells acting as a sink to remove that substance would create a balanced situation leading varying concentrations of that substance depending on its distance from the source. Cells close to the source would be exposed to high levels of the morphogen while those further away would see lowe
Contact: Kim McDonald
University of California - San Diego