Abstract: Gaurav AHUJA

Deorphanizing crypt neurons, the third type of olfactory receptor neurons

---

Gaurav Ahuja, Sigrun I. Korsching

Institut für Genetik, Universität zu Köln, Zülpicher Strasse 47a, 50674 Köln, Germany

---

The sense of smell (olfactory sense) plays a vital role in many essential behaviors such as prey detection, predator evasion and reproduction. The small teleost Danio rerio (zebrafish) has been established as model system to study vertebrate olfaction. In the olfactory epithelium of Danio rerio, there are four types of olfactory sensory neurons (OSNs) present: ciliated, microvillous, kappe and crypt neurons. Olfactory receptors present on ciliated and microvillous neurons have been studied extensively, but little is known about the receptors, transducing G-protein and further information processing in kappe and crypt neurons. Here we characterized a robust and reliable marker for the crypt neurons, which specifically labels neuronal somata, axons, and terminals in zebrafish. It reveal a single glomerulus, mdg2 of the dorsomedial group, as target glomerulus of crypt neurons. Furthermore, double immunohistochemistry with anti-Ora4 and anti-tubulin (ciliary marker) antibodies suggest that Ora4 receptor preferentially localises with cilia which resides in the eponymous crypt of the crypt neurons. By using heterologous expression, we have identified a specific ligand for Ora4 receptor and validated its physiological role in vivo by immunostaining with immediate early gene markers and thorough behavioural analysis. Furthermore we show that Gi1b is expressed near the crypt region, an ideal location for signal transduction from the olfactory receptor. Our data provide strong evidence that crypt neurons converge onto a single glomerulus, and that their ligand elicits odor-mediated behavioural responses in zebrafish.