Gene clue to the way people learn and memorise

Researchers are using advanced genetic techniques to explain how memory and learning take place in the human mind and in time might be able to define how genes affect behaviour.

The difficulty is being able to make definitive associations between how an organism behaves and the substances being expressed by its genes, explained Prof Tim Tully of Cold Spring Harbor Laboratory, a private, non-profit research institute on Long Island, New York.

Prof Tully delivered a keynote address last night on the molecular basis of learning and memory to the Neuroscience Symposium underway at Trinity College Dublin. He described key work done at his laboratory on the role of the protein, CREB, in memory.

He described as a "big leap" any attempt to connect a single gene and its related protein to an aspect of behaviour. Such a leap had to be made in two steps. The first involved associating biochemical function to cell function and the second involved deciding how a change in cell function changed a behavioural function.

The problem was that most researchers were only looking at the initial step. Scientists were not looking at the second and "were not comfortable" with it because it involved something as difficult to define as behaviour. Central to these behavioural studies is the fruit fly, drosophila. It has only about 15,000 to 20,000 genes, a fifth the number in a human. Various genes can be switched on or off using genetic technologies and subsequent changes in fly behaviour can be studied.

Findings using fruit flies can in turn be compared to what happens in humans because many of the genes and proteins in the two species are the same. Many of the genes which evolved in lower organisms were retained by higher organisms as they in turn evolved so there is a surprising degree of commonality even across species.

He studies the connections between genes and behaviour using "vertical integration" and "horizontal integration". The former involves making a change to a drosophila gene and then studying each of the knock-on effects that arise, from inside the cell through to behavioural change.

The latter involves looking for parallels across species, for example, looking for a common gene and related protein in a fruit fly, mouse and human. If all three have the gene then there is a probability that it will have a common function in each, despite the radical differences between species.

In this way CREB's ability to improve memory was discovered. Fruit flies with enhanced levels of CREB were able to learn faster compared with control flies. Further research showed that in fact CREB's action was to allow the flies to imprint memory faster after fewer exposures to a stimulus.