THIS WEEK:                                                           17 Jan 98
 #15  A cure in sight: Pinning down the cataract trigger could help millions of
          sufferers.

   By PHILIP COHEN
Poor communication between cells in the eye may explain why the lenses of
elderly people often turn hazy with cataracts, a study in mice suggests. The
discovery may lead to drugs that can stop cataracts forming.
Most people over 60 will suffer from cataracts, a clouding of the eye caused
by the aggregation of lens proteins known as crystallins. Every year,
millions of patients worldwide need costly surgery to replace the foggy lens
and restore their vision. So-called 'nuclear' cataracts cause the greatest
problems because they form near the centre of the lens.
Geneticists hoped that by tinkering with crystallin genes they might be able
to trigger and study the formation of nuclear cataracts in animals-but so
far they have failed. Now Norton Gilula of the Scripps Research Institute in
La Jolla, California, and his colleagues suggest that the true cause of
cataracts may lie not in crystallin genes, but in the ability of cells in
the eye to communicate with their neighbours.
In experiments using mice, Gilula's team disrupted the gene for an eye
protein called a3 connexin. This forms channels in eye cells that allow them
to exchange chemical messages. Mice lacking a working connexin gene were
born with clear, normal eye lenses. But two to three weeks later, the
centres of their lenses started to lose clarity.
By the age of two months, 15 per cent of the crystallin protein in the
mutant mouse lenses had aggregated, suggesting that some chemical signal
which normally passes through the connexin channel prevents aggregation
(Cell, vol 91, p 833). 'If we could deliver that molecule with eye drops,
we'd have a potent treatment for delaying cataracts,' Gilula suggests.
'It's a very exciting piece of work,' says Sam Zigler, a biochemist who
studies crystallin structure at the National Eye Institute in Washington DC.
'It provides the first animal model for nuclear cataracts, and they are the
most important clinical problem.'

New Scientist
Volume  157.   Issue   2117.
Copyright (C) IPC Magazines Ltd, 1985-1997



Bud Kennedy
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