OR Genes and Axonal Projections in Zebrafish

Thanks to Buck and Axel and colleagues, most neuroscientists are aware of the precise topographical map of the mouse olfactory nerve projection in which each olfactory sensory neuron (OSN) expresses a single odorant receptor (OR), and OSNs expressing a given OR converge on a set of glomeruli in the olfactory bulb. This week, Sato et al. mapped the zebrafish axonal projection using a bacterial artificial chromosome transgene. The transgene contained a cluster of 16 OR genes, two of which (OR111–7 and OR103–1) were replaced with yellow and cyan membrane-targeted reporters. Distinct sets of OSNs were fluorescently labeled, whereas their axons targeted the same cluster of glomeruli. For the OR111 subfamily, each OSN expressed a single OR, but a few OSNs coexpressed OR111 and OR103 subfamily members, and OR103–1 was always coexpressed with OR103–2/103–5. Such dual receptor expression has also been seen in Drosophila. Maybe fish are a bit more like flies than mice in this case.

See Yuki Sato, Nobuhiko Miyasaka, and Yoshihiro Yoshihara in the Journal Of Neuroscience