BERKELEY -- Three blind mice: See how they run.
That's what scientists have been doing at UC-Berkeley, and they've made a startling discovery that raises hopes for a treatment someday to restore vision in people.
When injected with a chemical, these blind mice scurried away from bright light -- instead of ignoring it, as expected.
Never available to nursery rhyme creatures, the new chemical makes "blind" cells in the retina responsive to light, said lead researcher Richard Kramer.
"Our molecule is light sensitive," said Kramer, UC-Berkeley professor of molecular and cell biology who along with colleagues at the University of Washington, Seattle published the study in Thursday's issue of the journal Neuron. "It has the potential for restoring visual function."
Nocturnal denizens of dark and gloomy places, mice usually go to great lengths to avoid light. But when blind, they don't care, and will scamper anywhere, dark or bright.
When the chemical AAQ was injected into the eyes of blind lab mice and an LED lamp illuminated one corner of their cage, they acted like regular mice, "turning around and running away, pointing their head in the opposite direction," he said.
There was additional proof of light sensitivity: Their pupils contracted when a bright light was shone in their faces.
This approach could eventually help those with blindness caused by the death of light-sensitive cells in the retina, the rods and
cones.
One common disease of this type is retinitis pigmentosa, a hereditary disease that causes continual loss of peripheral vision and slowly steals sight. Former San Francisco mayor and Assembly Speaker Willie Brown lives with this disease, forcing him to listen intently and memorize vast amounts of information.
It could also help those with age-related macular degeneration, the most common cause of acquired blindness in the developed world.
The chemical is essentially a "photoswitch" that binds to protein ion channels on the surface of retina cells. When switched on by light, AAQ alters the flow of ions through the channels -- and activates the neurons much the way rods and cones are activated by light.
"AAQ has the potential to be a powerful treatment because it may restore vision in people who are completely blind from a variety of diseases," says Dr. Stephen Rose, chief research officer, Foundation Fighting Blindness. "We are excited to see this research team move this approach closer to studies in humans."
The current version of AAQ wears off quickly. New versions -- that could activate neurons for days, not hours -- are being tested, said Kramer.
If proven successful in humans, the idea of simply injecting eyes to be sensitive to light has various advantages over other experimental approaches for restoring sight, such as implanting light-sensitive chips in the eye or inserting electrodes into the optic nerve to simulate the cell firings normally triggered by a visual scene.
It is also simpler, and less permanent, than genetically engineering light-sensitive cells.
"The advantage of this approach is that it is a simple chemical, which means you can change the dosage, you can use it in combination with other therapies, or you can discontinue the therapy if you don't like the results," Kramer said.
Contact Lisa M. Krieger at 650-492-4098.
