NESTED EXPRESSION DOMAINS FOR ODORANT RECEPTORS IN ZEBRAFISH OLFACTORY EPITHELIUM

The mapping of high-dimensional olfactory stimuli onto the two-dimensi onal surface of the nasal sensory epithelium constitutes the first ste p in the neuronal encoding of olfactory input. We have used zebrafish as a model system to analyze the spatial distribution of odorant recep tor molecules in the olfactory epithelium by quantitative in situ hybr idization. To this end, we have cloned 10 very divergent zebrafish odo rant receptor molecules by PCR. Individual genes are expressed in spar se olfactory receptor neurons. Analysis of the position of labeled cel ls in a simplified coordinate system revealed three concentric, albeit overlapping, expression domains for the four odorant receptors analyz ed in detail. Such regionalized expression should result in a correspo nding segregation of functional response properties. This might repres ent the first step of spatial encoding of olfactory input or be essent ial for the development of the olfactory system.