A Subcircuit in the Suprachiasmatic Nucleus Generates Wakefulness

Area of Science:

• Neuroscience
• Chronobiology
• Molecular Biology

Background:

• Circadian rhythms govern daily sleep-wake cycles, with the suprachiasmatic nucleus (SCN) as the master pacemaker.
• The molecular mechanisms linking the SCN to arousal remain largely unknown.
• The Wide Awake (WAKE) molecule and its homolog mWAKE are implicated in arousal pathways.

Purpose of the Study:

• To investigate if mWAKE marks an arousal-promoting SCN subcircuit in mice.
• To elucidate the role of SCN mWAKE neurons in regulating arousal and circadian rhythms.

Main Methods:

• Utilized chemogenetics and optogenetics to manipulate mWAKE-expressing cells in the SCN.
• Performed genetic knockout of mWAKE and impaired CLOCK function in SCN neurons.
• Examined SCN mWAKE neuron activity and their projections to the subparaventricular zone (SPZ).

Main Results:

• Chemogenetic activation of mWAKE+ cells increased wakefulness; inhibition induced stupor.
• Optogenetic activation of SCN mWAKE neurons promoted arousal.
• mWAKE knockout or CLOCK impairment in SCN neurons enhanced nighttime wakefulness.
• SCN mWAKE neuron signaling to the SPZ amplified arousal responses.

Conclusions:

• The mWAKE-expressing SCN subcircuit is crucial for regulating arousal.
• These findings highlight conserved genetic mechanisms controlling circadian arousal.
• A clock-regulated neural network involving SCN mWAKE neurons and the SPZ is defined for rhythmic arousal.