Our latest work towards repairing vision loss was published in PLoS ONE today. My students and I created genetically modified zebrafish that allowed us to kill a small subset of the cone photoreceptors in the retina (cones are for daytime/colour vision, as opposed to rods for nighttime vision). We then traced the subsequent events and observed that the stem cells in the retina were activated and replaced the lost cone photoreceptors.

This creates a great tool for us going forward to try and understand how stem cells can be instructed to generate cones - recent work in mice used stem cell therapy to replace rods in an stunningly successful manner (mice are nocturnal and have few cones) but for these therapies to be useful for clinical treatments it is important to replace cone photoreceptors and repair the patient's daytime vision. Our work provides some hope that if stem cells were applied to or activated within the region of the human retina with most of our cones (the macula or fovea), then the stem cells might be more likely to become cones, as compared to the difficulties being observed with this strategy in mice. The next steps in our research are well-underway, and we have some hot leads to identify the switches (genetic & cellular interactions) that instruct stem cells to become cones instead of rods.

As much as these potential clinical applications are keeping us on our toes, I am equally excited that we were able to create a genetically modified fish that loses and regenerates cones in manner very similar to trout and salmon. The technology requires some improvements, but I think this approach will finally let me address the most fascinating questions emerging out of my PhD thesis work at UVic: why would such an unusual set of events in the salmon retina? what are the advantages of cones dying and regenerating during the salmon's migration to and from the ocean?

Please check out the article, freely available online.

 http://dx.plos.org/10.1371/journal.pone.0055410