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
