Laurent Seugnet

Research interests: neuroglia signaling, sleep/wake regulation, learning and metabolism

Key words: Sleep/wake, learning, glia, neuro-glia signaling, metabolism, glycaemia, Notch, Gap junctions, lysosome, blood brain barrier.

Which cells and molecular pathways are preferentially affected by extended waking? What are the restorative functions controlled by sleep? How is sleep allowing those restorative processes to take place? These long standing questions remain largely unanswered. Answers to these questions will increase our awareness of the importance of sleep function and may lead to new therapeutic strategies. Our work addresses these questions using a combination of behavioral genetics, gene profiling and pharmacological approaches in the model organism Drosophila melanogaster. Drosophila has been at the leading edge of research in the field of circadian rhythms, neurodegenerative processes, learning and memory, synaptic physiology and can be used as an effective model organism to study sleep function. Sleep analysis in flies is based on behavioural criteria and its automation allows sleep monitoring and manipulation in large numbers of flies. Current projects explore the role of neuro-glia signaling in sleep/wake regulation and learning, an aspect which has been largely ignored in sleep research until recently. We also use the Drosophila model to identify sleep/wake regulatory genes in combination with mouse of models of narcolepsy and somnolence developed by Jian-Sheng Lin in the laboratory. We have a developing interest in the interactions between sleep and metabolism, notably glycaemia, to test hypothesis based on human data.

Biosketch

I did my PhD in the laboratory of Pat Simpson in Strasbourg (P. Simpson is now in the department of Zoology, Cambridge university), working on the early neural development in Drosophila. I then did my postdoctoral training in the laboratory of Michael Bate (Cambridge University) on the development of neuronal circuits, and in the laboratory of Paul Shaw (Washington University School of Medicine) on the molecular genetics of sleep in Drosophila. I worked for one year in the laboratory of Thomas Préat (ESPCI, Paris) on the link between sleep and long term memory, before joining my current position.

Selected publications :

Dissel, S., L. Seugnet, M. S. Thimgan, N. Silverman, V. Angadi, P. V. Thacher, M. M. Burnham and P. J. Shaw (2014). "Differential activation of immune factors in neurons and glia contribute to individual differences in resilience/vulnerability to sleep disruption." Brain Behav Immun. pii: S0889-1591(14)00472-3.
  • Le Glou E, Seugnet L, Shaw PJ, Preat T, Goguel V. (2012) Circadian modulation of consolidated memory retrieval following sleep deprivation in Drosophila. Sleep 35:1377-1384B. 2012.
  • Seugnet L., Suzuki Y., Merlin G., Gottschalk L., Duntley S.P., Shaw P.J (2011) Notch signaling modulates sleep homeostasis and learning after sleep deprivation in Drosophila. Curr Biol. 21, 835-40
  • Seugnet L., Suzuki Y., Donlea J.M., Gottschalk L., Shaw P.J. (2011) Sleep deprivation during early-adult development results in long-lasting learning deficits in adult Drosophila. Sleep, 34, 137-46
  • Seugnet L., Suzuki Y., Thimgan, M., Israel, S.L., Duntley, S.P., Shaw, P.J. (2009) Identifying sleep regulatory genes using a Drosophila model of insomnia. J Neurosci. 29, 7148-57.
  • Seugnet L., Suzuki Y., Vine L., Gottschalk L., Shaw P.J (2008) D1 receptor activation in the mushroom bodies rescues sleep-loss-induced learning impairments in Drosophila. Curr Biol. 18, 1110-7.
  • Seugnet L., Botero J., Gottschalk L., Duntley S.P., Shaw P.J. (2006) Identification of a biomarker for sleep drive in flies and humans. PNAS, 103, 19913-8.

Other Lab members involved in this research

Principal investigators

  • Jian-Sheng Lin
  • Karine Spiegel
  • Patricia Franco

Postdoc

  • Abud Farca-Luna

PhD Student

  • Sami Aboudhiaf

Research Master Student

  • Zaynab Muguet

Research assistants

  • Magali Perier
  • Christelle Daude
  • Laeticia Achaintre
  • Ophélie Jourjon

Collaborations

  • Paul Shaw (Washington University School of Medicine, St Louis, USA)
  • Jean-Marie Petit (Ecole Polytechnique Fédérale de Lausanne)
  • Christian Giaume (Collège de France, Paris)
  • Karim Benchenane (Ecole Supérieure de Physique Chimie Industrielle, Paris)
  • Yaêl Grosjean (Centre des Sciences du Goût et de l'Alimentation, Dijon)
  • André Klarsfeld, Serge Birman (Ecole Supérieure de Physique Chimie Industrielle, Paris)
  • Jean-François Ghersi-Egea (CRNL, Lyon)

Three frequently asked questions

1) How is sleep recorded in Drosophila?

Sleep monitoring in flies is based on locomotor activity. Usually, this is done using the trikinetics DAM system (http://www.trikinetics.com/): each fly is housed individually in a glass tube (diameter: 5mm, length: 60mm) with food at one end and a foam plug at the other. The number of times the animal crosses an infrared beam in the middle of the glass tube is recorded [1-3]. Infrared video recording methods are also used [4] (http://www.pysolo.net/). In all cases, periods exceeding 5 minutes without locomotor activity are considered sleep: they are associated with decreased sensitivity to external sensory stimulation, and homeostatic regulation [1, 3]. It is worthy of note that periods exceeding 5 minutes without any locomotor activity have also been evaluated as an 80% reliable marker of sleep in honeybees, although antennae movement are usually used to monitor sleep in this species [5] (see also question 2). Monitoring locomotor activity to estimate total sleep is not a methodology restricted to insects: in mice maintained in laboratory conditions, a system based on the breaking of infrared beams has also been designed for high throughput sleep monitoring and has been shown to be over 90% accurate [6]. Monitoring locomotor activity is also used for monitoring sleep in the zebrafish [7].

2) Is there any slow wave sleep and/or REM (Rapid Eye Movement or paradoxical sleep)

sleep in flies?

Electrophysiological recording of local field potentials have shown that sleep is associated with changes in neuronal activity in the Drosophila brain [8, 9]. No activity similar to that seen during slow wave sleep or REM sleep has been observed in these studies. One measure of sleep quality in Drosophila is sleep bout duration. During the lights on period (“day”) sleep occurs in short bouts, whereas sleep is more abundant and occurs in longer bouts during the night (lights off). Drosophila is diurnal and most of its sleep occurs during the night. Interestingly, the longest sleep bout of the day is usually observed in the first hour of the night. This is reminiscent of what happens during the first sleep cycle of the night in humans, which is usually characterized by the longest episode of the deepest stage of slow wave sleep. Interestingly, sleep in bees can be evaluated by monitoring the movements of their highly mobile antennae, and several distinct stages in sleep can be defined using this method [5]. So far, no electrophysiological study of cerebral activity during sleep in bees has been reported.

3) How are flies deprived of sleep?

Usually flies are kept in Trikinetics tubes for sleep monitoring (see question 1) and sleep deprivation is carried out by tilting the tubes at regular intervals (several times/ minute) to elicit a locomotor response (negative geotaxis reflex). Automated systems such as the SNAP (Sleep Nullifying Apparatus) have been designed for this purpose [3]. A treadmill like system [10], or placing two flies in the same tube [11] have also been used as alternative sleep deprivation methods. Sleep deprivation by any of these methods is followed by a sleep rebound: an increase in sleep over usual daily amounts. This increase is proportional to the amount of sleep lost and reveals the homeostatic regulation of sleep. Constant light [12] or starvation [13, 14], also reduce sleep but are associated with significant side effects.

References

  1. Hendricks, J.C., Finn, S.M., Panckeri, K.A., Chavkin, J., Williams, J.A., Sehgal, A., and Pack, A.I. (2000). Rest in Drosophila is a sleep-like state. Neuron 25, 129-138.
  2. Andretic, R., and Shaw, P.J. (2005). Essentials of sleep recordings in Drosophila: moving beyond sleep time. Methods Enzymol 393, 759-772.
  3. Shaw, P.J., Cirelli, C., Greenspan, R.J., and Tononi, G. (2000). Correlates of sleep and waking in Drosophila melanogaster. Science 287, 1834-1837.
  4. Zimmerman, J.E., Raizen, D.M., Maycock, M.H., Maislin, G., and Pack, A.I. (2008). A video method to study Drosophila sleep. Sleep 31, 1587-1598.
  5. Eban-Rothschild, A.D., and Bloch, G. (2008). Differences in the sleep architecture of forager and young honeybees (Apis mellifera). J Exp Biol 211, 2408-2416.
  6. Pack, A.I., Galante, R.J., Maislin, G., Cater, J., Metaxas, D., Lu, S., Zhang, L., Von Smith, R., Kay, T., Lian, J., et al. (2007). Novel method for high-throughput phenotyping of sleep in mice. Physiol Genomics 28, 232-238.
  7. Rihel, J., Prober, D.A., and Schier, A.F. Monitoring sleep and arousal in zebrafish. Methods Cell Biol 100, 281-294.
  8. Nitz, D.A., van Swinderen, B., Tononi, G., and Greenspan, R.J. (2002). Electrophysiological correlates of rest and activity in Drosophila melanogaster. Curr Biol 12, 1934-1940.
  9. van Swinderen, B., Nitz, D.A., and Greenspan, R.J. (2004). Uncoupling of brain activity from movement defines arousal States in Drosophila. Curr Biol 14, 81-87.
  10. Seugnet, L., Suzuki, Y., Vine, L., Gottschalk, L., and Shaw, P.J. (2008). D1 receptor activation in the mushroom bodies rescues sleep-loss-induced learning impairments in Drosophila. Curr Biol 18, 1110-1117.
  11. Gilestro, G.F., Tononi, G., and Cirelli, C. (2009). Widespread changes in synaptic markers as a function of sleep and wakefulness in Drosophila. Science 324, 109-112.
  12. Harbison, S.T., and Sehgal, A. (2009). Energy stores are not altered by long-term partial sleep deprivation in Drosophila melanogaster. PLoS One 4, e6211.
  13. Thimgan, M.S., Suzuki, Y., Seugnet, L., Gottschalk, L., and Shaw, P.J. (2010). The perilipin homologue, lipid storage droplet 2, regulates sleep homeostasis and prevents learning impairments following sleep loss. PLoS Biol 8.
  14. Keene, A.C., Duboue, E.R., McDonald, D.M., Dus, M., Suh, G.S., Waddell, S., and Blau, J. Clock and cycle limit starvation-induced sleep loss in Drosophila. Curr Biol 20, 1209-1215.