We’re publishing the shortlisted entries to the 2012 Wellcome Trust Science Writing Prize. In this piece, Elizabeth Hull describes how experiments in fruit flies are uncovering the genetics of sleep.
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Bed at 11, up at 6, that’s seven hours. Plenty of sleep.
1am. Ok, five hours now but I can still manage. Just need to fall asleep.
3am. Yes, 3am. Both clocks in the room are glaring with 3am. Still no sign of that sleep.
4am. Why do I waste time even trying?!
Sound familiar? Whether it’s that presentation on Friday or spending too much time at the computer, one in ten Britons can’t fall asleep at night. Stress and worry are often considered the main causes of sleepless nights. However, the clue to why some of us struggle with sleep could be in our genes.
Scientists at Rockefeller University, New York, have revealed that a genetic mutation in fruit flies can prevent them from catching forty winks. This mutation, aptly named insomniac, was discovered by monitoring the sleep patterns of over 20,000 fruit flies. Measuring this is now an everyday science: a fly is placed into a sealed tube and an infrared beam directed down the centre. Each time the fly crosses the beam, an ‘activity event’ is recorded. Through collection of this information over several days, the fly’s activity can be monitored.
What makes a fly an insomniac? In this study, the average fruit fly was found to sleep for 927 minutes a day. Insomniacs and jealous types look away now – that’s over 15 hours! The insomniac flies did not sleep so well, dozing off for a mere (though still enviable) 317 minutes, just a third of the normal average time. Each period of sleep for these flies was also reduced, averaging 12 minutes of solid sleep in comparison to 48 minutes for the regular fly.
So how does this help us in our search for some shut-eye? Evidence strongly suggests that sleep is an ancient evolutionary behaviour, with the mechanisms of sleep being shared by mammals and invertebrates such as fruit flies. Two mechanisms called homeostatic and circadian processes control our sleep. Homeostatic regulation relates to our need for sleep. With this mechanism alone, we would feel at our brightest immediately after waking and get progressively sleepier as the day went on. The circadian mechanism, more commonly known as our ‘biological clock’, is responsible for those highs and lows of alertness we experience throughout the day. It controls the timing of sleep, and it is thanks to our circadian regulation that you still feel alert for a precious few hours even after little to no sleep. Given these shared mechanisms, it is anticipated that the study of fruit flies and their sleeping habits should help us to better understand the fundamentals of human sleep regulation.
So what is the effect of the insomniac gene? The evidence suggests that the circadian clock is intact in our sleepless flies; like all animals, they show the greatest propensity for sleep just after darkness, and this sleep drive reduces as the night goes on. However, the insomniac flies show a general reduction in sleep during the day and night, suggesting their homeostatic regulation has been affected. It is proposed that the insomniac gene destroys proteins important in the control of sleep and wakefulness in animals.
This is not the first time that proteins in the brain have been associated with restless nights. Researchers at the Howard Hughes Medical Institute, Pennsylvania, identified a gene in fruit flies essential for sleep and the recovery from sleep deprivation. Mutations in this gene, dubbed sleepless, resulted in flies that slept for as little as one hour a day. Sleepless is responsible for a protein believed to reduce the excitability of nerve cells in the brain. In these sleep-deprived flies, less of this protein was produced and so the brain stayed active, promoting wakefulness. This finding, like that in insomniac flies, links our homeostatic sleep drive to brain activity.
Does this mean genes could be the answer to your insomnia? The night is still young for the science of sleep. Several genes have now been implicated in sleep regulation and, although the fruit fly is a simple model, it is hoped that the identification of genes in these restless critters will assist in the discovery of human equivalents. If our genes are found to be responsible for that 3am clock-watching, they may prove to be the key to treating insomnia.
Learning that your insomnia could be genetic might not be the cure you were hoping for, but spare a thought for the insomniac flies. At least we have long hot baths and a cup of warm cocoa to fall back on!
Elizabeth Hull
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This is an edited version of Elizabeth’s original entry in the professional scientist category. Views expressed are the author’s own.
Find out more about the Wellcome Trust Science Writing Prize in association with the Guardian and the Observer and read our ‘How I write about science‘ series of tips for aspiring science writers.
Over the next couple of months, we’re publishing the shortlisted essays from the 2012 competition. Read them all, and the 2011 essays, in our archive.
Image credits: Cartoon Church (top); Wellcome Images (left)
References
- Stavropoulos, N. & Young, M.W. insomniac and Cullin-3 regulate sleep and wakefulness in Drosophila. Neuron 72 (6), 964-76 (2011) PubMed
- Koh, K. et al. Identification of SLEEPLESS, a sleep-promoting factor. Science 321, 372-6 (2008) PubMed
Filed under: Genetics and Genomics, Science Communication, Wellcome Trust Science Writing Prize Tagged: biological clock, circadian mechanism, Drosophila, Elizabeth Hull, Genetics, homeostasis, insomnia, Sleep Image may be NSFW.
Clik here to view.
Image may be NSFW.Clik here to view.
