Biologists at the University of California, San Diego have discovered that growing nerve cells in the developing embryo are guided to their proper targets by bursts of intracellular calcium that probe what's ahead and send back information to the cells in a kind of biological Morse code.
In a paper published in the March 9 issue of Science, the researchers report their discovery that finger-like projections on growing nerve cells, known as filopodia, sample the environment and generate tiny bursts of calcium at their tips that send back information in a manner similar to an FM radio, enabling the neurons to wire up proper connections in the developing brain, spinal cord, and other parts of an animal's body.
"These bursts, which usually occur at the very ends of the filopodia, are extremely brief-about a 300-millisecond pulse-which may explain why they were undetected in earlier studies," says Timothy M. Gomez, an assistant professor of anatomy at University of Wisconsin Medical School who headed the research while a postdoctoral fellow at UCSD. "Since many other types of cells have these finger-like projections, we believe that these brief calcium bursts may be a universal signaling mechanism for motile cells."
"Many kinds of birth defects and a large fraction of spinal cord defects appear to be associated with problems in the formation of nerve connections in the developing embryo," says Nicholas C. Spitzer, a professor of biology at UCSD, commenting on the wider implications of the discovery. "We want to understand how the normal brain is put together, so we can understand the cases in which it is not put together correctly."
In addition to Gomez and Spitzer, who headed the laboratory in which the research was conducted, others involved in the discovery were Mu-ming Poo, a UCSD professor of biology now at the University of California, Berkeley; and Estuardo Robles, an undergraduate at UCSD who is now a graduate
Contact: Kim McDonald
University of California - San Diego