DNA damage modulates sleep drive in basal cnidarians with divergent chronotypes
TL;DR
Imagine your nerve cells are tiny workers in a factory that runs all day. As they work, they make a small mess and sometimes break their tools (this is like DNA damage). Sleep is like the night-time cleaning and repair crew. It shuts down the main factory operations so the crew can come in, clean up the mess, and fix the broken tools. This study looked at the simplest, oldest factories in the animal kingdom—jellyfish and sea anemones—and found that they also need this nightly repair crew. When they were forced to stay 'awake,' the mess and broken tools piled up. This suggests that the need for a dedicated repair shift (sleep) is a very old and essential part of being an animal.
Sleep is a conserved behavior across all animals with a nervous system, ranging from cnidarians to humans. Considering the survival risks, why sleep evolved in basal lineages and what essential benefits it provides to the simple nerve net of nocturnal and diurnal invertebrates remain elusive. We used behavioral criteria to empirically define sleep in the upside-down jellyfish Cassiopea andromeda and the starlet sea anemone Nematostella vectensis. Light and homeostasis were the primary drivers of sleep in C. andromeda, which slept at night and napped at midday in both the laboratory and the natural habitat. In contrast, both the circadian clock and homeostatic processes regulated sleep in N. vectensis, which increased sleep at dawn. Similar to humans, C. andromeda, wild-type (WT) and Clock mutant (NvClkΔ/Δ) N. vectensis slept about one-third of the day, irrespective of the daily timing and architecture of sleep, and melatonin promoted sleep in accordance with the species-specific chronotype. Notably, sleep deprivation, ultraviolet radiation, and mutagens increased neuronal DNA damage and sleep pressure, while spontaneous and induced sleep facilitated genome stability in both the diurnal and crepuscular cnidarians. These results suggest that DNA damage and cellular stress in simple nerve nets may have driven the evolution of sleep.
- 1Sleep in Cassiopea andromeda is primarily driven by light and homeostasis, while in Nematostella vectensis, it is regulated by the circadian clock and homeostatic processes.
- 2Both species sleep about one-third of the day, similar to humans, and melatonin promotes sleep according to species-specific chronotypes.
- 3Sleep deprivation, UV radiation, and mutagens increase neuronal DNA damage and sleep pressure, while sleep facilitates genome stability.
- 4The study suggests that DNA damage and cellular stress in simple nerve nets may have driven the evolution of sleep.
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