Research News Getting nervous . . . . . . . . . . . . . . . But scientists at the University of California, Los Angeles, and the University of Michigan have found an intriguing molecule that may be part of the answer. Dscam receptors at the tip of the neuron receive signals from different parts of the brain, controlling the direction of growth. A receptor called Dscam, which is embedded in the outer membrane of the neuron, receives signals sent by other cells and these messages affect the direction in which the neuron grows.
Some signals repel, and others attract.
The researchers found that when the Dscam receptor malfunctions, the long stringy growth cone cannot find its target. In many Dscam mutants the neurons were unable to find the P2 neuron. Whether neurons lose their targeting ability in Down syndrome patients is not known. What researchers find most interesting about Dscam is that it is a modular gene with 24 segments, or exons. Whether all these forms are actually produced by the cell is not known, says Jack Dixon, who led the biochemical experiments in the study at the University of Michigan.