OLFACTION - TRANSIENT EXPRESSION OF A PUTATIVE ODORANT RECEPTOR IN THE AVIAN NOTOCHORD

In vertebrates, odors are thought to be detected by a multigene family encoding several hundreds of seven-transmembrane-domain G-protein-cou pled receptors found in fish, rat, moose, dog, and human, Recently, th e putative odorant receptor (OR) gene family in the chicken has been c haracterized, Twelve members have been isolated and subdivided irate s ix subfamilies. Herein, we have further characterized the chicken olfa ctory receptor subfamily 7 (COR7) composed of two highly related genes (named COR7a and COR7b) which are 98.5% identical, By in situ hybridi zation experiments, both COR7a and COR7b transcripts were detected in the olfactory epithelium from embryonic das 6 (E6) to the new born sta ge. Within the olfactory epithelium, the spatial distribution of COR7a and COR7b labeled cells was random, We also observed that every indiv idual positive cell did not coexpress the COR7a and COR7b genes. Inter estingly, the COR7b gene was found to be transiently expressed ire the notochord from E2 to E6, whereas COR7a or any of the other known memb ers of the COR gene family were not detected in this mesodermal tissue , These data suggest that, in addition to its potential role as an OR in the olfactory system, COR7b may also hare a function in the notocho rd that is essential for the dorsoventral organization or the neural t ube and of the somitic mesoderm. We also discuss the possible role(s) of a putative OR present in both the notochord and the sensory olfacto ry epithelium.