Regulation of Sleep by Environmental Light

Lead Research Organisation: University of Oxford
Department Name: Clinical Neurosciences

Abstract

We spend around a third of our lives asleep and sleep disruption is a major contributing factor to a health problems ranging from poor vigilance and memory, reduced reaction times, reduced motivation, depression, metabolic abnormalities, obestity, reduced immunity and elevated risks of cancer and coronary heart disease. Sleep is a complex process, involving multiple areas of the brain and numerous neurotransmitters. It is regulated by the familiar process whereby there is a increased requirement for sleep with prolonged waking (the sleep homeostat) as well as a drive for wakefulness produced by the body's internal 24h clock (circadian clock). In addition, environmental light plays a critical role in regulating the timing of the sleep/wake cycle as well as acute changes in sleep and arousal states. Changes in the light environment are detected by eye via a number of different photoreceptive cells. These include the rods and cones which mediate image-forming vision. However, the last decade has witnessed the remarkable discovery of a new class of light sensitive cell in the eye. A small subset of the retinal ganglion cells that form the optic nerve that projects to the brain have been found to be directly photosensitive (pRGCs) due to the presence of the light-sensing protein melanopsin. Rather than enabling us to create precise images of the external world, these cells simply detect the brightness of environmental light (irradiance), playing a critical role in many non-image forming responses such as setting the body clock to the day-night cycle and regulating sleep. As such, the eye performs two very different sensory tasks - firstly, to generate images of the world around us and secondly, to sample the light environment to regulate a range of non-image forming responses, including sleep. Recent studies have shown that mice lacking melanopsin show reduced sleep when exposed to light during the night. However, the sleep timing with respect to the light/dark cycle is normal in these animals, and exposure to light at other times can still produce normal sleep responses. Our recent unpublished data show that whilst melanopsin contributes to sleep regulation in response to light, other photoreceptors also contribute. The light environment provides a complex stimulus, and as well as the irradiance, the wavelength and rate of change of the light are expected to determine which photoreceptors are involved. Little is known about the contribution of these photoreceptors under different lighting conditions, and as a result we have only a poor understanding of the optimum light environment for housing laboratory mice. This proposal aims to determine the contribution of rods, cones and melanopsin pRGCs to the regulation of sleep under different lighting conditions. In mice, sleep is normally measured by electroencephalography (EEG) which involves implanting electrodes to measure electrical activity of the brain. In mice, this is invasive as well as time-consuming and expensive. We have recently developed a method of measuring sleep in mice using miniature night-vision cameras placed above the animal's cage. Using computer software to track the animal's movement, and defining sleep as a period of extended immobility we are able to measure sleep with remarkable precision compared to simultaneous EEG measures. We will use this non-invasive, high-throughput approach to study responses to light in a range of mouse models in which rods, cones and melanopsin are genetically altered. We will also screen sleep responses in mutant mice produced by MRC Harwell to identify novel genes which are involved in the regulation of sleep in response to light. This work will lead to a greater understanding of the role of rods, cones and melanopsin pRGCs in the regulation of sleep and is expected to improve our understanding of how retinal disease may give rise to sleep disruption.

Technical Summary

Sleep is the product of multiple brain structures and neurotransmitter systems. This coordinated neural activity in turn drives alternating patterns of behaviour characterised by changes in rest/activity, body posture and responsiveness to stimuli. In addition to homeostatic and circadian oscillators, environmental light plays a critical role in both the entrainment of the sleep/wake cycle and the acute modulation of sleep and arousal states. The intensity, duration, rate of change and spectral composition of the light environment all contribute to sleep regulation and this complex stimulus is decoded by multiple retinal photoreceptors. These photoreceptors include the rods and cones which mediate image-forming vision, as well as the recently identified photosensitive retinal ganglion cells (pRGCs) expressing the photopigment melanopsin. Melanopsin pRGCs mediate many non-image forming (NIF) responses to light, and recent studies have shown that the regulation of sleep is impaired in melanopsin knockout mice. However, this data does not preclude a contribution from rods and cones and our preliminary data using twilight simulation suggest that different photoreceptors may contribute, depending upon the nature of the stimulus. How the various photoreceptor classes interact in the intact retina and what features of the light environment are important remain unknown. This proposal will use both forward and reverse genetic approaches to define the contribution of different classes of photoreceptors to both the timing and direct effects of light on sleep regulation. Using high-throughput sleep scoring based upon video tracking we will study sleep in a range of photoreceptor transgenics in response to different environmental light stimuli. Behavioural data will be supported by the use of molecular and electrophysiological correlates of sleep. The results are expected to provide major advances in our understanding of how sleep is regulated by environmental light.

Planned Impact

The impact of this proposal is expected to extend well beyond the research community, building upon the existing communication networks and expertise of the applicants. Both Dr Peirson (SNP) and Prof Foster (RGF) have a track record in securing industrial collaborations, and given interest in high-throughput compound screening, this is expected to lead to further industrial partnerships. Strong research interaction between the Nuffield Laboratory of Ophthalmology (NLO) and the Oxford Eye Hospital (OEH) also enables engagement and involvement of those working in front-line health care, and presentations on the OEH lecture series and the NLO's annual 'Updates in Ophthalmology' meeting will enable both specific details and health care implications of this work to be communicated to health care professionals. Both SNP and RGF have been involved in communicating their research to third sector organisations such as the RNIB, and in addition SNP has been involved with presentations as part of workshops for both the NC3Rs as well as the Health Protection Agency. The applicants have a strong track record of innovation and developing novel research tools and applications. This background provides a working knowledge of the processes required to protect and exploit research findings, which may have applications far beyond the scope of the immediate project. Finally, the applicants have previously been involved in a range of public engagement events to aid the communication of research to people of all ages and backgrounds, and with the development of a new NLO website have a further tool to ensure the current proposal achieves the greatest possible impact. Dr Nolan (PMN) has been involved in numerous collaborations with industrial partners, clinicians and basic scientists. Projects have been specifically associated with screening for mutants in a number of phenotypic domains and with developing and refining novel phenotyping methodologies and technologies to characterise mouse mutant lines.

Publications

10 25 50
 
Description This project has characterised how light regulates sleep and which photoreceptors in the eye mediate these responses, as well as identifying novel genes involved in the regulation of sleep.

We have identified an important contribution of ultraviolet (UV) light in the regulation of non-image forming responses. Instead of the blue-sensitive cone photoreceptors found in the human retina, mice have UV sensitive photoreceptors, and these cells appear to provide an important contribution to the regulation of sleep. We have now extended these findings using a UV knockout model.

We have also characterised the role of melanopsin isoforms in the regulation of circadian rhythms, sleep and pupillary responses, showing that the different variants mediate different responses.

Our work on the regulation of sleep by light has revealed that different wavelengths (colours) of light produce dramatically different biological effects, with green light promoting sleep whereas blue light produces arousal. This work was published in PLOS Biology (Pilorz et al., 2016).

In addition, using a non-invasive video-tracking screen has allowed us to identify a mouse mutant which shows greatly reduced levels of sleep. This behaviour is inherited and we have now mapped the causative mutation to the SNARE complex protein VAMP2. These animals are now undergoing behavioural and EEG phenotyping. This approach to measuring sleep has also been applied to an aging screen, showing an increased fragmentation of sleep with age.

Finally, as a result of this work, we have developed a methods of non-invasively measuring body temperature using thermal imaging. We have also developed an open-source method of measuring combined circadian activity and sleep to enable other researchers to apply these methods to their research.
Exploitation Route The methods used in this research have received interest from pharmaceutical companies looking for assays to measure effects of novel compounds on sleep. The high-throughput non-invasive screening used in this work has attracted a great deal of interest from other researchers wanting to screen transgenic mice for sleep defects. Previously, such work required was invasive, time-consuming and often expensive. The methods we have published are now used by MRC Harwell, part of the International Mouse Phenotyping Consortium (IMPC), which is now screening sleep as part of its phenotyping pipeline.
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description As a result of our work, I have been invited to participate in a BBSRC funded sparking impact exhibition at the Museum of Natural History in Oxford (spring 2015) relating to the effects of light on the body clock. This has also generated interest from industry (Roche and Philips Lighting) and policy makers (Public Health England). Our developments in non-invasive assessment of physiology and behaviour in mice have also generated to considerable interest in the welfare community. As a result of work in this area, I have been appointed to the NC3Rs grant review panel, provided articles for the NC3Rs website, and have recently been invited to be part of a UK Home Office delegation to China regarding laboratory animal welfare. Finally, we have been approached by Dyson lighting to provide expert advice on their development of new lighting products.
First Year Of Impact 2015
Sector Energy,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Other
Impact Types Cultural,Societal

 
Description Guidelines on measuring light for non-image forming responses
Geographic Reach North America 
Policy Influence Type Citation in other policy documents
Impact "The proliferation of electric lighting was a hallmark of the 20th century, providing widespread access to light virtually anywhere, at any time of day. In the same way, the 21st century may become the age of lighting for physiological well-being-often referred to with the familiar catchphrase light and health. Recent research has greatly advanced the understanding that light not only enables vision, but is also a critical signal to our biological systems, affecting circadian rhythms, pupillary response, alertness, and more. However, applying early research findings to widespread lighting practices must be done with great caution, if it is ready to be done at all. After all, light as a drug is much different from light as a commodity." These guidelines are also been evaluated by the International Lighting Commission (CIE), regarding the introduction of new lighting standards
URL http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/light_and_health_fs.pdf
 
Description Clocks, Sleep, and the Ageing Brain
Amount SFr. 397,768 (CHF)
Funding ID 927 
Organisation Velux Foundation 
Start 01/2016 
End 12/2018
 
Title COMPASS 
Description Continuous Open Monitoring of Activity and Sleep Status (COMPASS) is a system for monitoring locomotor activity and sleep in laboratory mice. This is based on passive infrared (PIR) sensors linked to an Arduino microprocessor, providing an affordable system to allow researchers to incorporate assessment of sleep and activity into their research. 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2014 
Provided To Others? Yes  
Impact This tool has been used in the following research publications: Richardson K, Livieratos A, Dumbill R, Hughes S, Ang G, Smith DA, Morris L, Brown LA, Peirson SN, Platt FM, Davies KE, Oliver PL (2016).Circadian profiling in two mouse models of lysosomal storage disorders; Niemann Pick type-C and Sandhoff disease. Behav Brain Res. Jan 15;297:213-23. Pritchett D, Jagannath A, Brown LA, Tam SK, Hasan S, Gatti S, Harrison PJ, Bannerman DM, Foster RG, Peirson SN (2015). Deletion of Metabotropic Glutamate Receptors 2 and 3 (mGlu2 & mGlu3) in Mice Disrupts Sleep and Wheel-Running Activity, and Increases the Sensitivity of the Circadian System to Light. PLoS One. 2015 May 7;10(5):e0125523 Porter AJ, Pillidge K, Tsai YC, Dudley JA, Hunt SP, Peirson SN, Brown LA, Stanford SC (2015). A lack of functional NK1 receptors explains most, but not all, abnormal behaviours of NK1R-/- mice(1). Genes Brain Behav. 2015 Feb;14(2):189-99. 
 
Title COMPASS 
Description Continuous Open Mouse Phenotyping of Activity and Sleep Status. Open access tool for phenotyping sleep and circadian activity in laboratory mice. Published method (Brown et al., 2016 Wellcome Open Research), including all software, circuits and analysis toolboxes. System validated against gold standard measures for measuring sleep (EEG) and activity (wheel-running) in mice. 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2015 
Provided To Others? Yes  
Impact We have already published several papers using this method and have provided complete systems to ~6 other labs. Numerous other researchers in our field have also adopted the system. Since publication in November 2016, 321 views and 56 downloads. 
URL https://wellcomeopenresearch.org/articles/1-2/v1
 
Title Irradiance Toolbox 
Description Provides a tool to account for the effects of light on the rods, cones and melanopsin pRGCs in the retina. Published as supplementary methods to Lucas et al., 2014, Trends in Neurosciences. A rodent version was also provided. 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Year Produced 2014 
Provided To Others? Yes  
Impact Under consideration by the CIE (International Lighting Commission) Included in publication on LED lighting by the US Department of Energy 
URL http://www.eye.ox.ac.uk/team/principal-investigators/stuart-peirson
 
Description BBC News - Oxford 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact BBC News (Oxford) interview on work on the effects of light on sleep and arousal
Year(s) Of Engagement Activity 2016
 
Description Biosense - 3 month exhibition at the Natural History Museum (Oxford) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact One of 3 invited contributors to "Innovation through collaboration: development of a programme of exhibitions to showcase the University of Oxford's bioscience research." A BBSRC Sparking Impact Award, led by Prof Paul Smith (Oxford University Museum of Natural History). This involves the installation of a short-term display space in the main court of the Natural History Museum which will be used to showcase a rolling-programme of research outputs from selected Oxford University Departments. May 2015 - August 2015.
Year(s) Of Engagement Activity 2015
 
Description Cafe Scientifique 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Café Scientifique presentation at Henley. Consisted of 45 min talk and 60 minutes of subsequent discussion.

Generated considerable interest and follow-up questions
Year(s) Of Engagement Activity 2014
 
Description Light and the Body Clock 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Sleep and the brain event at St Hilda's College Oxford
Year(s) Of Engagement Activity 2017
 
Description Oxford Sparks Animation 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Animation describing the role of light in regulating our sleep and circadian rhythms and summarising the research going on in our Department
Year(s) Of Engagement Activity 2015
URL http://www.oxfordsparks.ox.ac.uk/what-makes-you-tick
 
Description Pint of Science 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Public talk on 'Light and the Body Clock' as part of the Pint of Science week of events
Year(s) Of Engagement Activity 2015
 
Description What does integrity in laboratory animal science mean to you? 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Invited to speak as part of the Laboratory Animal Science Association (LASA) annual meeting on research integrity. Provided overview from a PPL holders perspective. Audience included students, vets, Home Office inspectors, laboratory technicians and ethicists.
Year(s) Of Engagement Activity 2018
URL http://www.lasa.co.uk/lasa-annual-conference-2018/