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Lucas Group

Research

Using light to tell time

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The amount of light reaching the earth’s surface varies by up to 9 decimal orders from the darkest night to the brightest day. Organisms across the living world (including humans) use this highly predictable variation to tell time of day. We are interested in how mammals measure this change in light intensity, and what impact it has on their behaviour and physiology. We are also interested in whether they can use changes in other aspects of the light environment (e.g. colour) to tell time. Our work defines basic mechanisms, but keeps a close eye on practical implications and, in particular, how an understanding of the neurophysiology of these systems can inform the design and use of artificial lighting.

How inner retinal photoreceptors help us to see

Photoreception in the mammalian retina extends beyond rods and cones to encompass a small number of retinal ganglion cells that are directly light sensitive thanks to their expression of the photopigment melanopsin. Melanopsin photoreceptors play a central role in driving such reflex responses to ambient light as circadian entrainment and the pupil light reflex. We have been studying how melanopsin also helps us to see. We are interested in how melanopsin adjusts vision according to changes in ambient light, but our latest findings are leading us to also study how it contributes directly to detecting patterns.

Optogenetic application of animal opsins

The opsin family of proteins that support photoreception across the animal kingdom are light activated G-protein coupled receptors. As such they represent an attractive source of optogenetic tools to allow intracellular signalling pathways to be remotely controlled using light. We aim to exploit this potential by using naturally occurring and engineered opsins to achieve improved control of G-protein signalling in heterologous systems.

A particular focus is on whether expressing opsin photopigments in surviving neurones of the inner retina could provide a viable method for restoring vision to people suffering retinal degeneration. We have shown that a human protein (human rod opsin) can indeed support vision across a range of natural light intensities in a mouse model of this disease and are developing improvements to this approach.

See also: Measuring melanopic illuminance