Fruit fly's brain is studied for clues to how genes may affect human growth

]Scientists have enlisted an unlikely ally in efforts to understand the marvellous complexity of the human brain - the common fruit fly.

The bug, drosophilia, is playing a major role in brain research and how various genes might affect growth, behaviour and development, explained Prof Corey Goodman, of the University of California, Berkeley, and a research investigator with the Howard Hughes Medical Institute.

"We like to think of it as a little person with wings," Prof Goodman said yesterday at Trinity College Dublin during the first day of a three-day international conference on the biology of the brain. In his keynote address he looked at mechanisms which allow the brain to wire itself up and become functional.

There are trillions of brain cells, and each is connected to thousands of others in a network "more complicated than any computer".

His group and researchers around the world are studying how this is achieved by studying what takes place in the fruit fly brain. Drosophilia's grey matter is less complex, but many of the biochemical processes in its brain also occur in ours.

When these studies began 20 years ago it was never imagined that so many of the genes found in, say, an insect would be so highly conserved through the evolutionary process in more advanced species, he said. Understanding brain wiring in bugs can therefore provide insights into how our own brains begin to form.

There are between 100 and 1,000 substances involved in the process of wiring the human brain, Prof Goodman estimated. Some encourage cells to link up and others "repel" these connections. The formation of these cell-to-cell links has also been found to be a very dynamic process with constant variation in the substances coming into play, causing near-infinite variety in the way brain cells connect during growth.

Understanding how the brain establishes its information pathways is not just of academic interest: it could lead to future treatments for spinal injuries and nerve damage.

The repelling substances help to keep nerve growth in check, even after major damage when it would be in the body's interest to allow repair. The hope is that drugs or treatments can be developed that will temporarily block these inhibiting substances, allowing the nerve tissues to rejoin and return full function to paralysed limbs.

It will be years before enough is known to allow such treatments, but Prof Goodman believes they will come in his lifetime. "I think the field is fascinating because the brain is the great frontier," he said.