Scientists identify mechanism behind brain asymmetry

A team of UCL scientists has identified the mechanism which causes left-right asymmetry present in the brains of most animals, first evident at the time of early development. By studying brain development in zebrafish, PhD student Jenny Regan and colleagues at Professor Stephen Wilson's laboratory have demonstrated that competition between two sides causes the brain to become asymmetrical. Asymmetry is thought to be important to enable the two hemispheres to specialise and operate more efficiently. According to research published today in the journal 'Neuron', the UCL team have shown that a protein known as Fgf8 acts as a magnet to attract nerve cells to one side of the brain. 'Fgf8 is found in both sides of the brain, leading to a 'tug-of-war? competition between the two sides to attract the migrating group of nerves cells,' says Jenny Regan. 'This isn't a fair fight, however ' Fgf8 on the left-hand side has an ally to help it win the battle." A second protein, known as Nodal, is present only on the left and teams up with Fgf8 to attract the group of nerve cells, triggering a cascade of events that lead to asymmetric development of the brain, with neurons on the left making different connections to those on the right. The combined action of Fgf8 and Nodal ensures that when the asymmetry develops, it is usually in the same direction - this helps to explain why there is consistent handedness between individuals.