Timing of Locomotor Activity Circadian Rhythms in Caenorhabditis elegans

Abstract

Circadian rhythms are driven by endogenous biological clocks and are synchronized to environmental cues. The chronobiological study of Caenorhabditis elegans, an extensively used animal model for developmental and genetic research, might provide fundamental information about the basis of circadian rhythmicity in eukaryotes, due to its ease of use and manipulations, as well as availability of genetic data and mutant strains. The aim of this study is to fully characterize the circadian rhythm of locomotor activity in C. elegans, as well as a means for genetic screening in this nematode and the identification of circadian mutants. We have developed an infrared method to measure locomotor activity in C. elegans and found that, under constant conditions, although inter-individual variability is present, circadian periodicity shows a population distribution of periods centered at 23.9±0.4 h and is temperature-compensated. Locomotor activity is entrainable by light-dark cycles and by low-amplitude temperature cycles, peaking around the night-day transition and day, respectively. In addition, lin-42(mg152) or lin-42(n1089) mutants (bearing a mutation in the lin-42 gene, homolog to the per gene) exhibit a significantly longer circadian period of 25.2±0.4 h or 25.6±0.5 h, respectively. Our results represent a complete description of the locomotor activity rhythm in C. elegans, with a methodology that allowed us to uncover three of the key features of circadian systems: entrainment, free-running and temperature compensation. In addition, abnormal circadian periods in clock mutants suggest a common molecular machinery responsible for circadian rhythmicity. Our analysis of circadian rhythmicity in C. elegans opens the possibility for further screening for circadian mutations in this species.

Circadian regulation of olfaction and an evolutionarily conserved, nontranscriptional marker in Caenorhabditis elegans

“…Over the last decade, there have been numerous reports of daily rhythms in the soil-dwelling nematode, C. elegans (6)(7)(8)(9)(10)(11)(12), although the connection between molecules and behavior has been lacking. Reasons for this may include a lack of known clock gene homologs as starting points, a number of low-amplitude behavioral rhythms, and the use of conditions that are far from ecological.…”

“…Previously, protocols used for clock research on the nematode, C. elegans (6)(7)(8)(9)(10)(11)(12), have shown circadian rhythms in behaviors (e.g., locomotor activity, defecation, and pharyngeal pumping rate), metabolism (e.g., resistance to osmotic stress), or the expression of hundreds of genes without a connection to rhythmic behaviors. Clearly, taken together, one would conclude that the nematode has a circadian system.…”

Period homolog LIN-42 regulates miRNA transcription to impact developmental timing

“…4 Like other circadian rhythm behaviors, locomoter activity in C. elegans is entrainable by both light-dark cycles and low-amplitude temperature cycles. 5 Since lin-42 mutant worms display altered locomotor activity rhythms, 5 in addition to regulating many developmental events, LIN-42 also regulates circadian rhythmic behavior in C. elegans.…”

Molecular characterization of the transition to mid-life in Caenorhabditis elegans

“…Circadian rhythms in many organisms are temperature compensated using feedback regulation and have Q 10 values of 0.9-1.2 (Simonetta et al 2009;Ruoff and Rensing 2004;Pittendrigh 1960). In contrast, enzymatic reactions, biosynthetic pathways, cell growth, and respiration have Q 10 values of 2-3 and are not considered to be temperature compensated (Ruoff and Rensing 2004).…”