Fish May Hold Secret To Curing Blindness

April 18, 2009

Release from: Keith Bonnell
Canwest News Service (Canada)

A common aquarium fish could hold the secret to curing blindness in humans.

But to look for answers, Canadian researcher Ted Allison is going to have to make some zebrafish nearly colour-blind.

The assistant professor at the University of Alberta is launching a study of zebrafish, which have the ability to regenerate their photoreceptors. Photoreceptors are the cells in the retina that receive light signals and send a neural signal that is interpreted by the brain - the first steps in vision.

The zebrafish ``has stem cells all throughout its retina, and if we damage any of the neurons, they regenerate,'' Allison explains.

He plans to study that process and see how it could someday be used to let people see again.

``We're trying to take advantage of what the fish can do.''

Allison recently received $200,000 in provincial and federal funding to carry out the experiment.

For the experiment, researchers have made a ``transgenic'' zebrafish, one with new genes added to its genetic makeup in the lab. Those extra genes are meant to let researchers apply a chemical to the fish that will damage its photoreceptors in a way that will take away much of the fish's ability to see colour.

Researchers will then study how the fish regrows its photoreceptors. The process takes weeks in the fish, Allison said.

He said researchers want to learn which genes are telling the creature's stem cells to recreate the damaged photoreceptors, as opposed to other kind of cells.

``If we can figure out how the fish is doing it, then, in principle we can use stem cells in people and accomplish the same thing that the fish is doing naturally,'' Allison said.

``We're going to look at the retina to see how the retinas change and what genes are being turned on. Our grand goal would be to understand how to turn a stem cell into a photoreceptor.''

The ability to regenerate photoreceptors is common in fish and frogs, but not mammals.

Allison said it likely will be a couple of years before the researchers are ready to publish and ``at least a decade,'' before blind people can benefit from what they learn.

Still, he's hopeful the study will someday benefit those with macular degeneration, a common cause of blindness in older adults.

The study highlights the use of zebrafish, a six-centimetre long, nervous fish, which has replaced lab rats in many experiments in recent years.

It's easy to keep an abundance of the small fish, and it's also not difficult to genetically manipulate them as eggs.

Another University of Alberta researcher recently published a study into the ``fight-or-flight'' instinct of zebrafish that he says could someday help people with spinal-cord injuries.

Declan Ali, an associate professor at the University of Alberta, has been studying zebrafish as embryos so he can seen how they form the mental synapses that drive their escape instinct - that quick, darting movement you see when you tap on an aquarium.

Synapses are the points of contact between cells that let information pass.

The hope is that by understanding what has to happen for the synapses to form in zebrafish, researchers will eventually be able to come up with drugs or therapy that can duplicate the process in humans.

``We're trying to understand how the synapses are formed in zebrafish because we believe that formation, that process, as well as many of the proteins . . . are very similar to what would occur in humans,'' Ali said.

Ali and PhD student Shunmoogum Patten identified two proteins that they say are vital to strengthening the synapses that allow the escape instinct.

Their findings were published this month in the high-profile journal Proceedings from the National Academy of Sciences.

Figuring out how to reform synapses for people with nerve damage or spinal- cord injuries won't get disabled people walking again, however.

The major element that's still missing from the equation is the ability to regenerate dead or damaged nerve cells.

Unfortunately, research into how to regenerate nerve cells is progressing very slowly, Ali said.

If scientists do find a way to regenerate nerve cells, then the work on strengthening the synapses, so the cells can communicate - the process observed in the zebrafish - becomes relevant.