Olfactory‐enriched transcripts are cell‐specific markers in the lobster olfactory organ

Abstract

Genes expressed specifically in a tissue are often involved in the defining functions of that tissue. We used representational difference analysis of cDNA to amplify 20 cDNA fragments representing transcripts that were more abundant in the lobster olfactory organ than in brain, eye/eyestalk, dactyl, pereiopod, or second antenna. We then independently confirmed that the transcripts represented by these clones were enriched in the olfactory organ. The 20 cDNA fragments represent between 6 and 15 different genes. Six of the cDNAs contained sequences highly similar to known gene families. We performed in situ hybridization with these six and found that all were expressed in subsets of cells associated with the aesthetasc sensilla in the olfactory organ. Clones OET-07, an ionotropic receptor, and OET-10, an alpha tubulin, were specific to the olfactory receptor neurons. OET-02, a monooxygenase, was expressed only in the outer auxiliary cells. OET-03, a serine protease, was specific to the collar cells. OET-11, an alpha(2) macroglobulin, was expressed by the receptor neurons and the collar cells. OET-17, a calcyphosine, was expressed in the receptor neurons, inner auxiliary cells, and collar cells. The identities and expression patterns of these six transcripts predict involvement in both known and novel properties of the lobster olfactory organ.

Gene expression and specificity in the mature zone of the lobster olfactory organ

“…A sequence similar to Drosophila glutamate synthase, but only weakly similar to bacterial glutamate synthetases, corresponds with the hypothesis that lobster olfactory sensory neurons are glutamatergic. The ionotropic GABA and glutamate receptors correspond to evidence of modulation of olfactory receptor neuron sensitivity, especially at their axon terminals (39,40,76,83,84). The G␥ 1 heterotrimeric G protein subunit corresponds to the missing partner of G␣-and G␤-subunits previously identified as mediators of olfactory transduction (80,82).…”

“…The types of sequences with significant similarity to the ESTs ranged from intermediary metabolism enzymes to transcription factors, receptors, and neuropeptides (Tables 2 and 3). Among these were specific markers previously identified as associated with three cell types located in the mature zone of the olfactory organ: olfactory sensory neurons, auxiliary (glial) cells that ensheath the bundles of dendrites extending from each cluster of olfactory sensory neurons, and secretory cells of the aesthetasc tegumental glands (39,47,68,69). OET-07, an ionotropic glutamate receptor, and OET-10, a tubulin isoform, both of which are specifically expressed in olfactory sensory neurons, were detected.…”

“…Gene products typically enriched in neurons that we detected included N-cadherin, long-chain fatty acid-CoA ligase, ciboulot, phospholipase C, adenylyl cyclase, calmegin, Down syndrome cell adhesion molecule (Dscam), neuroligin, dorfin, orcokinin, synaptotagmin, failed axon connnections (Fax), trophinin, glutamate synthase, ionotropic glutamate and GABA receptors, GABA receptor-associated protein, chloride channels, and Na ϩ -K ϩ -ATPases. Some of these sequences, like those of phospholipase C, adenylyl cyclase, ionotropic receptors, and ion channels, are already known to be expressed by olfactory sensory neurons or are implicated in their physiology (21,39,40,79,83,84).…”

“…The breadth of sequences detected provides a more balanced view of gene expression in the olfactory organ than has been gathered by other approaches. For example, serine proteases and their inhibitors, which constitute a functionally related group that stood out in previous studies (39,71) of gene expression in the olfactory organ, were rivaled or surpassed by dehydrogenases, kinases, transporters and channels, and regulators of transcription and translation.…”

Molecular characterization and histochemical demonstration of salmon olfactory marker protein in the olfactory epithelium of lacustrine sockeye salmon (Oncorhynchus nerka)

“…The EphB2 receptor is a tyrosine kinase that is activated by interaction with B-type ephrins, a family of closely related axonal guidance factors (Himanen et al, 1998;Cramer et al, 2006). In invertebrates, several ORN-specific marker proteins have been identified from the olfactory organs (e.g., lobster, Homarus americanus, Hollins et al 2003; land snail, Eobania vermiculata, Mazzatenta et al 2004). However, these amino acid and nucleotide sequences indicated that these molecules of the invertebrates were not homologous to vertebrate OMP including salmon OMP.…”