ASYNCHRONOUS ONSET OF ODORANT RECEPTOR EXPRESSION IN THE DEVELOPING ZEBRAFISH OLFACTORY SYSTEM

The functional identity of an olfactory neuron is determined in large part by the odorant receptors it expresses. As an approach toward unde rstanding the events that underlie the specification of olfactory neur ons, we have examined the patterns of odorant receptor gene expression in the developing zebrafish. Surprisingly, we find that the onset of specific odorant receptor expression occurs asynchronously in the deve loping olfactory placode. Our results suggest that odorant receptor ex pression is not strictly stochastic, but rather is governed by tempora lly regulated cues during development. Moreover, by restricting the nu mber of receptor genes competent for transcription at different times of development, temporal waves of expression may provide a mechanism f or simplifying the regulation of the large odorant receptor gene famil y.