Dynamically-expressed prion-like proteins form a cuticle in the pharynx of Caenorhabditis elegans.

In molting animals, a cuticular extracellular matrix forms the first barrier to infection and other environmental insults. In the nematode Caenorhabditis elegans there are two types of cuticle: a well-studied collagenous cuticle lines the body, and a poorly-understood chitinous cuticle lines the pharynx. In the posterior end of the pharynx is the grinder, a tooth-like cuticular specialization that crushes food prior to transport to the intestine for digestion. We here show that the grinder increases in size only during the molt. To gain molecular insight into the structure of the grinder and pharyngeal cuticle, we performed a microarray analysis to identify mRNAs increased during the molt. We found strong transcriptional induction during the molt of 12 of 15 previously identified abu genes encoding Prion-like (P) glutamine (Q) and asparagine (N) rich PQN proteins, as well as 15 additional genes encoding closely related PQN proteins. abu/pqn genes, which we name the abu/pqn paralog group (APPG) genes, were expressed in pharyngeal cells and the proteins encoded by two APPG genes we tested localized to the pharyngeal cuticle. Deleting the APPG gene abu-14 caused abnormal pharyngeal cuticular structures and knocking down other APPG genes resulted in abnormal cuticular function. We propose that APPG proteins promote the assembly and function of a unique cuticular structure. The strong developmental regulation of the APPG genes raises the possibility that such genes would be identified in transcriptional profiling experiments in which the animals' developmental stage is not precisely staged.

DAF-16/FOXO regulates homeostasis of essential sleep-like behavior during larval transitions in C. elegans.

Sleep homeostasis, which refers to the maintenance of sleep amount or depth following sleep deprivation, indicates that sleep and sleep-like states serve fundamental functions that cannot be bypassed [1]. Homeostasis of sleep-like behavior is observed during C. elegans lethargus, a 2-3 hr behavioral quiescent period that occurs during larval state transitions [2]. Here, we report a role for DAF-16/FOXO, a transcription factor that is active under conditions of stress [3], in the response to deprivation of lethargus quiescence. Forced locomotion during lethargus results in nuclear translocation of DAF-16. The formation of dauer larvae, a developmental state promoted by daf-16, is increased in response to quiescence deprivation. daf-16 mutants show an impaired homeostatic response to deprivation of lethargus quiescence and are hypersensitive to the lethal effects of forced locomotion during lethargus. DAF-16 expression in muscle cells, but not in neurons, is sufficient to restore a homeostatic response to deprivation of quiescence, pointing to a role for muscle in sleep homeostasis. These findings are relevant to clinical observations of altered metabolic signaling in response to sleep deprivation and suggest that these signaling pathways may act in nonneuronal tissue to regulate sleep behaviors.