How neurons get wired.

• Position: The Brain - Brief article

An unknown mechanism that establishes polarity in developing nerve cells has been discovered by scientists at the University of Arizona, Tucson. Understanding how nerve cells make connections is an important step in developing cures for nerve damage resulting from spinal cord injuries or neurodegenerative diseases such as Alzheimer's.

Doctoral student Sara Parker and her advisor, assistant professor of cellular and molecular medicine Sourav Ghosh, report that the decision which will be the "plus" and the "minus" end in a newborn nerve cell is made by a long and a short version of the same signaling molecule.

Nerve cells--or neurons--differ from many other cells by their highly asymmetric shape: vaguely resembling a tree, a neuron has one long, trunk-like extension ending in a tuft of root-like bristles. This is called the axon. From the opposite end of the cell body, branch-like structures known as dendrites sprout. By connecting the "branches" of their dendrites to the "root tips" of other...