Strongly alkaline pH avoidance mediated by ASH sensory neurons in C. elegans

Area of Science:

• Neuroscience
• Sensory Biology
• Molecular Biology

Background:

• High pH poses a survival risk to animals, necessitating effective avoidance mechanisms.
• The specific sensory pathways for detecting high pH have remained largely undetermined.
• The nematode Caenorhabditis elegans exhibits avoidance behavior for environmental pH above 10.5.

Purpose of the Study:

• To elucidate the molecular and cellular mechanisms underlying high pH sensation in Caenorhabditis elegans.
• To identify the specific neurons and ion channels involved in detecting alkaline environments.

Main Methods:

• Analysis of Caenorhabditis elegans mutants with defects in sensory cilia.
• Genetic rescue experiments to pinpoint critical genes and neurons.
• Laser ablation of specific neurons (ASH) to assess functional roles.
• In vivo calcium imaging to monitor neuronal activity in response to high pH.

Main Results:

• Mutants with abnormal sensory cilia failed to avoid high pH, implicating ciliary sensory neurons.
• ASH polymodal sensory neurons were identified as crucial for high pH avoidance.
• TRPV ion channels encoded by osm-9 and ocr-2 were found to be essential for high pH sensing.
• ASH neurons showed high pH-evoked calcium influx, which was absent in osm-9 and ocr-2 mutants.

Conclusions:

• High pH is sensed by ASH nociceptors in Caenorhabditis elegans.
• The OSM-9/OCR-2 transient receptor potential vanilloid type (TRPV) channels in ASH neurons mediate the detection of alkaline pH.