Mice may shed light on mental disability

By HOLLY LAKE, Ottawa Sun

Dr. David Picketts has high hopes for a little mouse. A decade after discovering the gene responsible for a severe form of mental retardation while at Oxford University, his team at the Ottawa Hospital Research Institute has now created a mouse model with the same gene, known as ATR-X.

Picketts said the animal model was crucial to really grasp how the ATR-X gene works and the resulting ATR-X syndrome that develops when the gene doesn't act as it should.

"It's very difficult to try and understand the role of any gene in complex diseases of the human brain," he said. "By creating this model, we're able to understand the mechanisms by which ATR-X functions."

Over the next five to seven years his team of researchers, as well a team he's collaborating with at Oxford, hope to learn more about the gene by looking at the mouse brain throughout its development. The key is the model mimics the human disease in early brain development.

"That will lead us down potential routes for possible future therapeutic intervention," Picketts said. "There's also always the possibility for stem cell therapy, but we just don't know enough about the gene and its mechanisms to say that yet."

EVERYONE HAS GENE

While everyone has the ATR-X gene, its inactivity in a rare few leads to a severe mental disability. There are only about 200 known cases of ATR-X syndrome worldwide, five of which are in Canada. It only affects boys and leaves them dependent on others for almost all daily living activities.

"All their developmental milestones are delayed," Picketts said."They're usually quite happy, friendly boys, but most patients don't walk until late in childhood, most have very little or no speech in addition to this severe mental handicap."

But because it can present itself in different ways in different people, experts are sure there are more cases out there.

"It's really hard to diagnose the disease, so we're continuously trying to identify new cases and see this whole spectrum disease," he said.

BRAIN 30% SMALLER

The brain of a child with an inactive ATR-X gene looks normal, but is about 30% smaller than it should be. That means crucial connections and brain wiring may not be present.

An article on the discovery appears in today's Journal of Clinical Investigation. holly.lake@ott.sunpub.com

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