Epidermal Growth Factor Signaling Promotes Sleep through a Combined Series and Parallel Neural Circuit.

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Sleep regulation involves sleep-active neurons inhibiting wakefulness.
• Homeostatic mechanisms dictate sleep need, but the underlying molecular and circuit processes are unclear.
• The RIS neuron is crucial for sleep in C. elegans.

Purpose of the Study:

• To investigate the molecular mechanisms translating sleep need into sleep-active neuron depolarization.
• To define the transcriptome of the RIS neuron and identify its signaling pathways.
• To elucidate the role of the ALA neuron in sleep regulation and its connection to RIS.

Main Methods:

• Transcriptome analysis of the RIS neuron.
• Investigation of Epidermal Growth Factor Receptor (EGFR) signaling in RIS and ALA neurons.
• Behavioral analysis of C. elegans under various conditions, including cellular stress.

Main Results:

• EGFR signaling pathway genes are expressed in the RIS neuron.
• EGFR signaling directly activates RIS neurons, particularly under cellular stress.
• The ALA neuron, identified as a drowsiness neuron, activates RIS and inhibits behaviors like feeding independently.
• ALA activation is crucial for survival during cellular stress, while RIS is not.

Conclusions:

• EGFR signaling influences sleep through both direct activation of RIS and indirect activation via ALA.
• ALA exhibits dual functions: independent behavioral inhibition and activation of RIS.
• ALA-mediated drowsiness, not solely RIS-mediated sleep, is vital for stress survival, highlighting distinct roles of behavioral inhibition in health restoration.