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 Friday, 24 January, 2003, 14:27 GMT
Poor memory linked to gene
Brain
Memory is dependent on cells making connections
A subtle alteration in one specific gene may play a crucial role in determining the power of a person's memory.

On average, people with a particular version of the gene performed worse in memory tests such as recalling what happened yesterday.

This appears to be due to abnormal activity in an area of the brain called the hippocampus which is known to control memory, and a failure of their brain cells to make the necessary connections to their neighbours for memories to be stored.

The problem seems to be linked to a chemical called brain derived neurotrophic factor (BDNF) which is required to keep brain cells healthy.

Production of this chemical is controlled by one particular gene.

But scientists have discovered that some people have a version of this gene that not only produces BDNF in lower than normal quantity, it produces a type which does not move around brain cells in the way it should.

Inheritance

People inherit two copies of the BDNF gene - one from each parent - in either of two versions.

Slightly more than a third inherit at least one copy of a version nicknamed 'met' which is only different from the standard version in the tiniest of ways.

It is this version which appears to lower BDNF production, and damage memory.

The researchers believe 'met' may play a role in the development of Alzheimer's and other neurological conditions.

But they also believe it probably has a positive effect which has yet to be pinned down.

The researchers, from the US National Institute of Mental Health and the US National Institute of Child Health and Human Development, examined data collected for another study in schizophrenia.

They found people who had inherited two copies of the 'met' gene scored significantly lower in tests measuring ability to recall events after a delay.

Brain scans also revealed that people carrying the 'met' gene had different levels of activity in the hippocampus.

And chemical tests showed that their brain cells were less healthy and less likely to make connections with their neighbours.

Strange movement

The researchers then used fluorescent tags to try to pinpoint the reason for this lack of communication.

They found that BDNF produced by the standard version of the gene spreads throughout the cell and into the branch-like structures that form connections with neighbouring cells.

But BDNF produced by the 'met' variation of the gene tended to clump in the centre of the cell, and not to spread into the areas where connections are made.

The researchers now plan to examine the role of BDNF in the development of Alzheimer's disease, depression and normal ageing.

Researcher Dr Daniel Weinberger said: "One can imagine that a condition like Alzheimer's disease, that destroys the hippocampus, may produce more dramatic effects or have a worse or more rapid course in individuals who have the met BDNF genes.

"Similar phenomena may also occur with normal aging and in depression."

The research is published in the journal Cell.

See also:

10 Mar 02 | Health
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27 Feb 02 | Health
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