Cnidarian Circadian Rhythms
Circadian rhythms regulate many aspects of animal biology, from cycles of sleep and wakefulness to variations in energetic metabolism. We study circadian regulation in the sea anemone Nematostella both to gain insight into cnidarian physiology and to better understand the evolution of the animal circadian clock.
A few things we’ve learned and questions that still keep us up at night:
- Nematostella shares many conserved circadian regulatory genes with other (bilaterian) animals. There is an ancient origin of circadian signaling in animals. But key circadian genes (period, timeless) seem to be restricted to bilaterians. How does the clock function in Nematostella without these pieces?
- Nematostella clearly has a circadian timer that regulates activity patterns and expression of several genes. But how does circadian regulation affect the physiology of these animals? Why do they need a clock at all??
- We’ve learned that light, especially blue light, can entrain circadian rhythms in Nematostella. What are the roles of temperature and/or other environmental cues in entraining the circadian clock? How do temporal rhythms differ between lab and field settings?
- How do redox state and other aspects of cellular physiology cycle over daily or tidal periods?
In our investigations of circadian signaling in Nematostella, We are currently collaborating with Dr. Oren Levy at Bar-Ilan University (Israel) through a grant sponsored by the Gordon and Betty Moore Foundation.
Notes on Cellular Redox
Our investigations of circadian regulation have been steering us toward improving our understanding of cellular redox state. Managing redox state is a normal part of cellular physiology, but harsh environmental conditions can disrupt this balance and create oxidative stress. Antioxidant enzymes like superoxide dismutase, catalase and peroxiredoxin enable cells to neutralize oxidants and maintain a healthy environment. Peroxiredoxins are very abundant antioxidants that have been relatively unstudied in invertebrates, including cnidarians.
In a recent paper, we show that Nematostella contains four peroxiredoxin genes, one of which belongs to a previously undescribed cnidarian-specific group. The genes vary in their inducibility by environmental stressors (elevated temperature, reduced salinity). While peroxiredoxin oxidation state is a deeply conserved part of cellular signaling, peroxiredoxin expression does not always exhibit a daily cycle. We have not observed a consistent daily cycle in peroxiredoxin expression in Nematostella.
We are currently working in visualization of cellular redox state in Nematostella.