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Updated: Jul 6, 2026

Quadruple Immunostaining of the Olfactory Bulb for Visualization of Olfactory Sensory Axon Molecular Identity Codes
Published on: June 5, 2017
BIG-2 mediates olfactory axon convergence to target glomeruli
Tomomi Kaneko-Goto1, Sei-Ichi Yoshihara, Haruko Miyazaki
1Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan.
BIG-2/contactin-4 is an axonal glycoprotein crucial for forming the odor map. In BIG-2-deficient mice, olfactory sensory neurons innervate multiple glomeruli, disrupting the odor map organization.
Area of Science:
- Neuroscience
- Molecular Biology
- Developmental Biology
Background:
- Olfactory sensory neurons (OSNs) project axons to specific glomeruli in the olfactory bulb, forming a precise odor map.
- The molecular mechanisms guiding OSN axon convergence onto glomeruli are complex and not fully understood.
Purpose of the Study:
- To investigate the role of BIG-2/contactin-4, an immunoglobulin superfamily glycoprotein, in the formation and maintenance of the olfactory odor map.
- To determine if BIG-2 influences OSN axon targeting and glomerular organization.
Main Methods:
- Immunohistochemical analysis of BIG-2 expression in mouse olfactory sensory neurons.
- Examination of glomerular arrangement in the olfactory bulb using BIG-2, Kirrel2, and ephrin-A5 markers.
- Analysis of olfactory sensory neuron targeting in BIG-2-deficient mice.
Main Results:
- BIG-2 is expressed in a subpopulation of OSNs, showing a mosaic pattern in the olfactory bulb.
- BIG-2 expression levels correlate with odorant receptor choice in individual OSNs.
- BIG-2-deficient mice exhibit ectopic innervation of multiple glomeruli by OSNs expressing a given odorant receptor.
Conclusions:
- BIG-2/contactin-4 is a key axon guidance molecule essential for the precise formation and maintenance of the functional odor map.
- BIG-2 plays a critical role in ensuring that OSN axons from a single receptor type converge onto specific glomeruli.
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