Oxyopia Abstract

April 10, 2009
Friday, 4:00 PM
489 Minor Hall

Inigo Novales Flamarique, PhD
Associate Professor, Simon Fraser University, Burnaby, British Columbia, Canada; Visiting scientist, U.S.-Canada Fulbright Chair at the Neuroscience Research Institute, UC Santa Barbara
Host: Dennis Levi

Title

Transcriptional regulation of opsin expression and its ecological significance

Abstract

Cone photoreceptors in the vertebrate retina express visual pigment proteins (opsins) which when combined with a light sensitive chromophore (a vitamin A derivative) form molecular complexes maximally sensitive to ultraviolet (UV), blue, green or red light. It is the combination of outputs from multiple cone types (each expressing a different predominant opsin) that allows colour vision to take place. Until recently, every cone was thought to express one predominant opsin class throughout its life. Our work on the retina of salmonid fishes has shown that cones switch opsin expression during ontogeny. Young fish have single cones that express a UV opsin ( max of the visual pigment ~ 365 nm) at hatching, and these cones switch opsin expression to blue ( max of the visual pigment ~ 433 nm) as the animal grows. The switch is mediated by a surge in thyroid hormone coupled to an up-regulation of thyroid hormone alpha receptor in cones undergoing the switch. Similar opsin switches have now been shown in multiple taxa, including mammals, where they are believed to play an important role in establishing the chromatic organization of the retina during embryogenesis. Using the stickleback retina, we have further shown that opsin switches can occur within a few generations following changes in the light environment experienced by the animal. This Îrapid evolutionâ has important consequences for understanding visual system plasticity and its ecological significance.

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