Assaying sensory ciliopathies using calcium biosensor expression in zebrafish ciliated olfactory neurons

Area of Science:

• Neuroscience
• Cell Biology
• Genetics

Background:

• Primary cilia act as scaffolds for signaling proteins, receptors, and ion channels, crucial for cellular communication.
• Ciliated olfactory sensory neurons (OSNs) in zebrafish utilize cilia to detect odorants via calcium influx.
• Zebrafish possess distinct ciliated and microvillus OSN types with varying odorant sensitivities.

Purpose of the Study:

• To investigate the role of sensory cilia in zebrafish OSN odorant detection using live imaging.
• To establish a quantitative model for analyzing sensory cilia signaling in vivo.
• To determine the impact of specific gene mutations on ciliated OSN function and odorant sensitivity.

Main Methods:

• Transgenic expression of the calcium biosensor GCaMP5 in OSNs for real-time response analysis.
• Comparison of olfactory responses in wild-type zebrafish with oval/ift88 mutant and ift172 knockdown models.
• Assessment of ciliated OSN sensitivity to various odorant classes, including bile acids, food odors, and amino acids.

Main Results:

• ift88 mutants and ift172 knockdown zebrafish exhibited significantly shortened OSN cilia but maintained OSN numbers.
• Reduced OSN cilia led to significantly decreased response fractions and amplitudes to bile acids and food odors.
• Odorant responses to amino acids remained largely unaffected in the mutant and knockdown zebrafish.

Conclusions:

• ift172 deficiency is identified as a novel cause of hyposmia (reduced sense of smell).
• The study validates a quantitative in vivo model for studying sensory cilia signaling.
• Hyposmia resulting from cilia dysfunction can serve as a diagnostic indicator for ciliopathies.