Blind World Magazine

Melanopsin causes nerve cells to become photoreceptive.
Research Could Lead To New Treatments for Blindness.

September 12, 2005.

Visual Loss and Blindness Treatment - Scientists have discovered how to make cells sensitive to light in what may lead to a new approach to treating certain forms of blindness.

The research, published in the science journal Nature, shows that a gene called melanopsin causes nerve cells to become photoreceptive.

The team of experts from The University of Manchester and Imperial College London found that activating melanopsin in cells that don't normally use the gene makes them sensitive to light.

"The melanopsin made the cells photoreceptive which tells us that this protein is able to absorb light," said Dr Rob Lucas, who led the team in Manchester.

"This discovery might provide food for thought for scientists looking for ways of treating visual loss."

Dr Lucas, whose research concerns the effect light has on our daily rhythms, said the classical view of how the eye sees is through photoreceptive cells in the retina called rods and cones.

However, Dr Lucas and Professor Hankins were part of a team that recently discovered a third type of photoreceptor, although the mechanisms of how it worked had not been fully understood - until now.

"Over the last few years it has become increasingly accepted that we have a third system that uses melanopsin and has lain undetected during years of vigorous scientific investigation," said Dr Lucas.

"For this latest research, we introduced melanopsin to cells that do not normally use it. What we found is that the cell becomes photosensitised and is able to produce a biological signal.

"The discovery that melanopsin is capable of making cells photosensitive has given us a unique opportunity to study the characteristics of this interesting protein."

For some years scientists have been exploring ways of restoring light detection to those blind people who have lost their rods and cones.

One implication of this research is that using melanopsin to make nerve cells in the eye photoreceptive may represent an entirely new approach to this problem.

Co-author and leader of the London team, Professor Mark Hankins of Imperial College, said: "It is quite remarkable that the activation of a single gene can create a functional photoreceptor."

"It is an important proof of principle that melanopsin can make non-light sensitive cells receptive to light and, although not a cure, could have applications in treating some forms of blindness."

Researchers also believe that defects in melanopsin action could be responsible for other human conditions, including some sorts of depression and insomnia.

"The truth is, we just don't know what else melanopsin could be responsible for," said Dr Lucas. "But now that we understand the role of this gene we can further investigate its influence in such areas as mood and sleep patterns."

The research team is collaborating with engineers at Imperial to develop a functional retinal prosthesis that would allow information from the light-responsive cells to be used by the brain to form images.

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