title: Lethargus is a Caenorhabditis elegans sleep-like state.
abstract: There are fundamental similarities between sleep in mammals and quiescence in the arthropod Drosophila melanogaster, suggesting that sleep-like states are evolutionarily ancient. The nematode Caenorhabditis elegans also has a quiescent behavioural state during a period called lethargus, which occurs before each of the four moults. Like sleep, lethargus maintains a constant temporal relationship with the expression of the C. elegans Period homologue LIN-42 (ref. 5). Here we show that quiescence associated with lethargus has the additional sleep-like properties of reversibility, reduced responsiveness and homeostasis. We identify the cGMP-dependent protein kinase (PKG) gene egl-4 as a regulator of sleep-like behaviour, and show that egl-4 functions in sensory neurons to promote the C. elegans sleep-like state. Conserved effects on sleep-like behaviour of homologous genes in C. elegans and Drosophila suggest a common genetic regulation of sleep-like states in arthropods and nematodes. Our results indicate that C. elegans is a suitable model system for the study of sleep regulation. The association of this C. elegans sleep-like state with developmental changes that occur with larval moults suggests that sleep may have evolved to allow for developmental changes.
authors.affiliation: Center for Sleep and Respiratory Neurobiology, University of Pennsylvania School of Medicine, 3400 Spruce Street, Philadelphia, Pennsylvania 19104, USA. raizen@mail.med.upenn.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Raizen
authors.forename: John E
authors.initials: JE
authors.lastname: Zimmerman
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Maycock
authors.forename: Uyen D
authors.initials: UD
authors.lastname: Ta
authors.forename: Young-jai
authors.initials: YJ
authors.lastname: You
authors.forename: Meera V
authors.initials: MV
authors.lastname: Sundaram
authors.forename: Allan I
authors.initials: AI
authors.lastname: Pack
mesh_terms: D000818:Animals; D001143:Arousal / Q000235:genetics / Q000502:physiology; D005075:Biological Evolution; D017173:Caenorhabditis elegans / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence / Q000235:genetics; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D007814:Larva / Q000502:physiology; D053609:Lethargy; D018978:Molting / Q000502:physiology; D012890:Sleep / Q000235:genetics / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D017869:Cyclic GMP-Dependent Protein Kinases; C470349:EGL-4 protein, C elegans