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A new molecular alarm clock in vertebrates

Dozens of chemical interactions in the vertebrate brain go into maintaining a natural sleep schedule, and scientists have recently found one more player on the field: a neurochemical called neuromedin U, or Nmu. The protein, which was analyzed in zebrafish but is also found in humans, acts to stimulate wakefulness, particularly in the morning. The study appears in Neuron.

“We found a gene that’s involved in promoting wakefulness and suppressing sleep, and only a handful of genes have been shown to do that,” says senior author David Prober, a sleep biologist at the California Institute of Technology. Prober and his colleagues uncovered the gene’s function in a large-scale screening project.

Researchers have studied the underpinnings of sleep for decades, but many of the genes and proteins that scientists have found to affect the sleep/wake cycle in mammals were discovered serendipitously. These discoveries don’t yet tell the whole story – so in a bid to uncover new parts of the system, Prober and his collaborators Jason Rihel and Alex Schier turned to zebrafish, which share brain structures related to sleep with humans.

This image is of a brain from a five-day-old zebrafish larva showing neurons that are activated in response to Nmu overexpression
This image is of a brain from a five-day-old zebrafish larva showing neurons that are activated in response to Nmu overexpression. Neurons expressing the gene corticotropin releasing hormone (crh) are labeled bright green, and neurons that express cfos, a marker of general neuronal activity, are labeled magenta. The image shows that crh-expressing neurons in the hindbrain are activated by Nmu overexpression. Scale bar = 100 ┬Ám.
Image Credit: Chiu et al./Neuron 2016