Characterisation of circadian and circannual rhythms in arctic reindeer
We aim to characterise the basic features of circadian and circannual organisation in 18 reindeer of both sexes and to explore the interaction between these levels of temporal control. Preliminary studies suggest that reindeer have weak circadian organisation at the behavioural and molecular level, but we lack the necessary detailed analysis to support this inference. As a large diurnal mammal, the reindeer provides an excellent model for understanding the impact of arctic lighting conditions on the human circadian system. Additionally we wish to determine the extent to which current models for photoperiodic synchronisation of annual cycles of physiology, which have been developed in temperate species, are relevant for arctic seasonal mammals. This topic is highly relevant to efforts to understand how climate change will impact seasonal adaptation in species living at high latitudes.
Our working hypothesis is that the reindeer has a functioning circadian system which is sensitive to environmental lighting, and specifically to dampening during prolonged exposure to continuous light (arctic summer) or darkness (arctic winter). To test this we will run longitudinal experiments in reindeer held under semi-natural and artificial lighting regimes in the AAB facility in Tromsø.
Using 18 semi-domesticated reindeer (6 male, 12 female), made tame through handling in early life, we will assess the state of the circadian system by round the clock, minimally invasive blood sampling at six different times of year: roughly every two months. At each of these times of year animals will be sampled indoors under simulated natural lighting conditions, and then under constant dim red light. This allows direct effects of the light-dark cycle to be resolved from effects due to an internal circadian clock. Blood samples will be analysed for plasma hormone (melatonin, cortisol) levels, and processed for transcriptomic profiling of gene expression in the white blood cells. These assays allow different circadian outputs to be resolved from one another, which is important for a proper characterisation of the system.
In addition, we will use Actiwatches to record locomotor activity. Food intake will be measured at 20 min intervals and body mass daily for one week every 2 months, while animals are outdoor in individual fences. The combination of this range of minimally invasive long term data recording technique are essential for proper interpretation of the hormonal and gene expression data we will gather.
We will collect skin biopsies under local anaesthesia for use in a real-time in vitro analysis of the reindeer circadian clock, based on cultured fibroblast monolayers that can be transfected with molecular probes (luciferase reporter gene constructs). This will enable molecular circadian oscillations to be recorded by luminometry. By taking biopsies at the 6 times of year as used for the blood sampling, we will be able to determine whether environmental lighting conditions influence the ability of reindeer fibbroblasts to maintain circadian rhythmicity.
Finally, we will use a new, minimally invasive technique to measure sleep rhythms in reindeer, when animals are undisturbed between sampling periods.
Our working hypothesis is that the reindeer has a functioning circadian system which is sensitive to environmental lighting, and specifically to dampening during prolonged exposure to continuous light (arctic summer) or darkness (arctic winter). To test this we will run longitudinal experiments in reindeer held under semi-natural and artificial lighting regimes in the AAB facility in Tromsø.
Using 18 semi-domesticated reindeer (6 male, 12 female), made tame through handling in early life, we will assess the state of the circadian system by round the clock, minimally invasive blood sampling at six different times of year: roughly every two months. At each of these times of year animals will be sampled indoors under simulated natural lighting conditions, and then under constant dim red light. This allows direct effects of the light-dark cycle to be resolved from effects due to an internal circadian clock. Blood samples will be analysed for plasma hormone (melatonin, cortisol) levels, and processed for transcriptomic profiling of gene expression in the white blood cells. These assays allow different circadian outputs to be resolved from one another, which is important for a proper characterisation of the system.
In addition, we will use Actiwatches to record locomotor activity. Food intake will be measured at 20 min intervals and body mass daily for one week every 2 months, while animals are outdoor in individual fences. The combination of this range of minimally invasive long term data recording technique are essential for proper interpretation of the hormonal and gene expression data we will gather.
We will collect skin biopsies under local anaesthesia for use in a real-time in vitro analysis of the reindeer circadian clock, based on cultured fibroblast monolayers that can be transfected with molecular probes (luciferase reporter gene constructs). This will enable molecular circadian oscillations to be recorded by luminometry. By taking biopsies at the 6 times of year as used for the blood sampling, we will be able to determine whether environmental lighting conditions influence the ability of reindeer fibbroblasts to maintain circadian rhythmicity.
Finally, we will use a new, minimally invasive technique to measure sleep rhythms in reindeer, when animals are undisturbed between sampling periods.