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F L Margolis

Publications and source records attributed to F L Margolis.

At least 55 records · Page 3Linked to original sources
PubMed1994

Expressed sequence tags (EST) identify genes preferentially expressed in catfish chemosensory tissues.

Expressed sequence tags (ESTs) for the catfish (Ictalurus punctatus) were identified and characterized by shotgun sequencing coupled to Northern analysis. We have identified and characterized a number of cDNA clones from a catfish olfactory mucosal library that show differential tissue expression including several that are enriched in chemosensory tissue. Among the novel cDNA clones studied were an olfactory specific beta-tubulin and a novel member of the S-100 family of calcium-binding proteins that is highly expressed in barbel, olfactory mucosa and gill, but not in brain. Several clones of low abundance mRNAs were also identified, including one manifesting a basic-helix-loop-helix (b-HLH) motif that is typical of many transcription factors. Additional cDNA clones whose mRNAs are differentially expressed, but are of unknown function, were also obtained. These results demonstrate the case with which novel gene products enriched in chemosensory tissues can be identified.

Amino Acid Sequence↗
PubMed1993

Presynaptic co-localization of carnosine and glutamate in olfactory neurones.

Olfaction plays a dominant role in modulating behaviour in most vertebrate species and the olfactory bulb is considered a model system for characterizing principles of neural computation. Nevertheless, although the physiology and neurochemistry of the olfactory circuits have been widely studied, the neurotransmitter released by olfactory receptor neurones remains unknown. We now describe the ultrastructural localization of the dipeptide carnosine and the excitatory amino acid glutamate in the glomerular layer of the mouse olfactory bulb. We demonstrate that both carnosine-like and glutamate-like immunoreactivities are selectively co-localized in the olfactory neurone boutons. These observations, taken with the recent findings of glutamate-receptor subunit expression in rodent olfactory bulb, argue compellingly for a role of glutamate in olfactory neurotransmission and suggest a modulatory effect of carnosine.

Animals↗
PubMed1993

From genotype to olfactory neuron phenotype: the role of the Olf-1-binding site.

The highly organized pattern of gene expression leading to the determination of cellular phenotype derives from the interplay between genetic and epigenetic factors. This is mediated in part by distinctive DNA sequence motifs present in the regulatory regions of various genes and the transcription factors with which they interact. The phenotype of olfactory neurons is determined in part by the selective expression of novel isoforms of several genes involved in chemosensory transduction. To characterize the mechanisms determining olfactory neuron phenotype we have been studying the olfactory marker protein (OMP), the first olfactory-specific protein to be isolated and cloned. The temporal and spatial expression of OMP is regulated stringently and is highly restricted to mature olfactory neurons in all vertebrates from amphibians to humans. Identification of the specific elements responsible for regulating the expression of the OMP gene will elucidate the mechanisms leading to the determination of olfactory neuron phenotype. Using a combined in vivo (transgenic mice) and in vitro (electrophoretic mobility shift assays and DNase I footprinting) approach, we have identified and characterized a novel genomic motif that binds an olfactory tissue nuclear protein(s) that we designate Olf-1. We propose that Olf-1 is a novel olfactory-specific transacting factor responsible for directing the expression of genes containing the Olf-1 motif in olfactory neurons. Thus it may play a role in regulating the expression of genes associated with neuronal turnover and olfactory transduction.

Animals↗
PubMed1993

Olf-1-binding site: characterization of an olfactory neuron-specific promoter motif.

We report characterization of several domains within the 5' flanking region of the olfactory marker protein (OMP) gene that may participate in regulating transcription of this and other olfactory neuron-specific genes. Analysis by electrophoretic mobility shift assay and DNase I footprinting identifies two regions that contain a novel sequence motif. Interactions between this motif and nuclear proteins were detected only with nuclear protein extracts derived from olfactory neuroepithelium, and this activity is more abundant in olfactory epithelium enriched in immature neurons. We have designated a factor(s) involved in this binding as Olf-1. The Olf-1-binding motif consensus sequence was defined as TCCCC(A/T)NGGAG. Studies with transgenic mice indicate that a 0.3-kb fragment of the OMP gene containing one Olf-1 motif is sufficient for olfactory tissue-specific expression of the reporter gene. Some of the other identified sequence motifs also interact specifically with olfactory nuclear protein extracts. We propose that Olf-1 is a novel, olfactory neuron-specific trans-acting factor involved in the cell-specific expression of OMP.

Aging↗
PubMed1992

Amphibian olfactory receptor neurons express olfactory marker protein.

Expression of olfactory marker protein (OMP) in olfactory receptor neurons (ORNs) in two amphibians was investigated by immunohistochemical methods. The OMP immunoreactivity was observed in the cilia, apical dendritic knobs, dendrites and somas of ORNs; the axons of ORNs also showed intense immunoreactivity for OMP throughout their course from the olfactory epithelium to the glomerular layer of the olfactory bulb. Seven days after olfactory nerve transection in salamander, the number of OMP-positive ORNs was markedly reduced in the ipsilateral epithelium. The results demonstrate that amphibian ORNs express OMP and confirm its phylogenetic conservation across diverse species.

Ambystoma↗
PubMed1992

Glutathione and gamma-glutamyl transpeptidase are differentially distributed in the olfactory mucosa of rats.

Components of the gamma-glutamyl cycle, including thiols, glutathione (GSH) and gamma-glutamyl transpeptidase (gamma-GT), were localized in the nasal mucosae of rats using histochemical and immunohistochemical methods. In olfactory mucosa, thiols were widely distributed, with intense staining in the mucociliary complex (MC), basal cells, acinar cells of Bowman's glands (BG), and olfactory nerve bundles, and with moderate staining in olfactory receptor neurons (ORNs). GSH was localized in MC, BG acinar cells, nerve bundles and, to a lesser extent, in ORNs. gamma-GT immunoreactivity was restricted to the MC and to basolateral and apical membranes of BG acinar and duct cells. The basolateral membrane of BG acinar cells, located in close association with blood vessels and connective tissue, showed granule-like immunoreactivity. In respiratory mucosa, all three compounds were localized in the MC and acinar cells of respiratory glands (RG). In the MC, gamma-GT immunoreactivity was associated primarily with brush borders of ciliated cells. Granular immunoreactivity was also apparent in the supranuclear region of RG acinar cells. These results demonstrate that components of the gamma-glutamyl cycle are localized in olfactory and respiratory glands, and that they are secreted into the mucus, where they may mediate perireceptor events such as detoxification and/or solubilization of air-borne xenobiotics, toxicants and odorants.

Animals↗
PubMed1992

Immunolocalization of B-50 (GAP-43) in the mouse olfactory bulb: predominant presence in preterminal axons.

Because the growth-associated protein B-50 (GAP-43) has been implicated in neurite outgrowth as well as in synaptic plasticity, we studied its light and electron microscopical distribution in the mouse olfactory bulb, an area of the nervous system which exhibits a high degree of synaptic plasticity. Immunofluorescent staining with monospecific affinity-purified anti-B-50 antibodies revealed that B-50 is most abundantly expressed in the olfactory nerve fibre layer and the granule cell layer neuropil, while little staining was observed in the external plexiform layer and in cell bodies. B-50 is absent from dendrites and myelinated axons as indicated by double labelling with monoclonal antibodies against microtubule-associated protein 2 and the large neurofilament protein, respectively. Using post-embedding immunogold labelling on ultrathin Lowicryl sections, B-50 was found to be highly concentrated in presumed growth cones in the olfactory nerve fibre layer and in thin unmyelinated axons and presynaptic terminals in the granule cell layer neuropil. Near background immunolabelling was seen in perikarya, dendrites and myelinated axons. In view of the implication of B-50 in plasticity-related phenomena, its abundance in the thin unmyelinated preterminal axons suggests that these are potential sites of extrasynaptic plasticity.

Animals↗
PubMed1992

Expression of olfactory receptors in Xenopus oocytes.

The rat olfactory epithelium and the amino acid-sensitive catfish olfactory system have been used as models to study the molecular mechanisms of olfactory transduction. Here we report the functional expression of rat and catfish olfactory receptors in Xenopus oocytes injected with mRNA isolated from the respective tissues. Application of odor ligands to injected oocytes, monitored by two-electrode voltage clamp, activates stimulus-dependent transmembrane currents that reverse direction at about the chloride equilibrium potential. The currents show characteristic secondary oscillations that are presumed to reflect underlying Ca2+ oscillations. Similar ligand-activated membrane currents induced in oocytes after injection of other mRNAs have been shown to be due to activation of endogenous Ca(2+)-activated chloride channels. In summary, our results demonstrate the usefulness of the Xenopus oocyte expression system for cloning and characterization of olfactory receptors in both fish and mammalian species.

Animals↗
PubMed1991

Carnosine in the brain and olfactory system of amphibia and reptilia: a comparative study using immunocytochemical and biochemical methods.

The pattern of distribution of carnosine-like immunoreactivity and its relation to glial fibrillary acidic protein immunoreactivity have been studied in two lizards (Gallotia galloti and Tarentola delalandii) and in two anuran amphibians (Rana esculenta and Xenopus laevis) using immunocytochemical techniques. Biochemical data obtained by paper electrophoresis show that the dipeptides carnosine and homocarnosine are both present in the brain of all the species examined. In the central nervous system of both anurans and reptilians, carnosine immunoreactivity is localized in glial cells. An important species difference is, however, seen in the olfactory system since primary olfactory neurons and their processes extending to the olfactory bulb are carnosine positive in reptiles, whereas they are not immunostained in anurans. Thus, the cellular distribution of carnosine immunoreactivity in reptilians is very similar to that observed in birds and mammals and is distinct from that seen in amphibia.

Animals↗
PubMed1991

Differential effect of functional olfactory bulb deafferentation on tyrosine hydroxylase and glutamic acid decarboxylase messenger RNA levels in rodent juxtaglomerular neurons.

Expression of the dopaminergic phenotype in olfactory bulb (OB) juxtaglomerular neurons (constituting a population of periglomerular and external tufted cells) is dependent upon functional innervation by peripheral olfactory receptors. Loss of functional input in rodents, by either peripheral deafferentation or deprivation of odorant access, results in a profound decrease in the expression of juxtaglomerular tyrosine hydroxylase (TH). We have examined the effects of such treatments on the expression of the neurotransmitter biosynthetic enzyme glutamic acid decarboxylase (GAD), which is colocalized with TH in the majority of TH-containing juxtaglomerular neurons. Following either chemically induced OB deafferentation in adult mice or unilateral odor deprivation in neonatal rats, steady-state OB GAD messenger RNA levels remained essentially unchanged as assessed by Northern blot analysis 20-40 days after treatment. These results were confirmed by in situ hybridization analysis, which demonstrated a profound loss of juxtaglomerular TH messenger RNA but no accompanying decrease in regionally colocalized GAD message. Since GAD is found in nearly all dopaminergic OB cells, the preservation of juxtaglomerular GAD message implies that olfactory receptor neurons exert a differential transneuronal regulation of TH and GAD gene transcription.

Animals↗
PubMed1991

Expression of calmodulin mRNA in rat olfactory neuroepithelium.

A calmodulin (CaM) cDNA was isolated by differential hybridization screening of a lambda gt10 library prepared from rat olfactory mucosa. This cDNA fragment, containing most of the open reading frame of the rat CaMI gene, was subcloned and used to characterize steady-state expression of CaM mRNA in rat olfactory neuroepithelium and bulb. Within the bulb mitral cells are the primary neuronal population expressing CaM mRNA. The major CaM mRNA expressed in the olfactory mucosa is 1.7 kb with smaller contributions from mRNAs of 4.0 and 1.4 kb. CaM mRNA was primarily associated with the olfactory neurons and, despite the cellular complexity of the tissue and the known involvement of CaM in diverse cellular processes, was only minimally evident in sustentacular cells, gland cells or respiratory epithelium. Following bulbectomy CaM mRNA declines in the olfactory neuroepithelium as does olfactory marker protein (OMP) mRNA. In contrast to the latter, CaM mRNA makes a partial recovery by one month after surgery. These results, coupled with those from in situ hybridization, indicate that CaM mRNA is expressed in both mature and immature olfactory neurons. The program regulating CaM gene expression in olfactory neurons is distinct from those controlling expression of B50/GAP43 in immature, or OMP in mature, neurons respectively.

Animals↗
PubMed1991

Regulation of gene expression in the olfactory neuroepithelium: a neurogenetic matrix.

The olfactory neuroepithelium exhibits neurogenesis throughout adult life, and in response to lesions, a phenomenon that distinguishes this neural tissue from the rest of the mammalian brain. The newly formed primary olfactory neurons elaborate axons into the olfactory bulb. Thus, denervation and subsequent reinnervation of olfactory bulb neurons may occur throughout life. This unique ability of the olfactory neuroepithelium to generate new neurons from a population of precursor cells present in the basal cell layer of this tissue makes it a valuable model in the study of neural development and regeneration. The molecular processes underlying the neurogenic properties of the olfactory neuroepithelium are poorly understood. Here we have reviewed our studies on the expression of B50/GAP43 during ontogeny of the olfactory system and following lesioning. This analysis includes the characterization of the expression of OMP, a protein expressed in mature olfactory neurons, as well as PKC and calmodulin. The latter two molecules are of particular interest to the function of B50/GAP43 since the degree of phosphorylation of B50/GAP43 appears to determine B50/GAP43's ability to bind calmodulin (see also Storm, chapter 4, this volume). In the mature olfactory epithelium B50/GAP43 expression is restricted to a subset of cells located in the basal region. Since the expression of B50/GAP43 is high in developing and regenerating nerve cells we are confident that the B50/GAP43 positive cells are new neurons derived from the stem cells in the basal region of the epithelium. B50/GAP43 is absent from the stem cells themselves and also from the mature OMP-expressing neurons. On the basis of the patterns of B50/GAP43 and OMP expression two stages could be discriminated in the regeneration of the olfactory epithelium. First, as an immediate response to lesioning a large population of B50/GAP43 positive, OMP negative neurons are formed. Subsequently, during the second stage, these newly formed differentiating neurons mature as evidenced by a decrease in B50/GAP43 and an increase in OMP expression. The second stage in the regeneration process is only manifested if the regenerating neurons can reach their target cells in the olfactory bulb. Hence, bulbectomy results in the arrest of the reconstituted olfactory epithelium in an immature state. The differential patterns of B50/GAP43 expression following peripheral lesioning and bulbectomy suggest the existence of a target derived signal molecule involved in the down-regulation of B50/GAP43 expression in olfactory neurons that have established synaptic contacts in the olfactory bulb (see also Willard, chapter 2, this volume, "the suppressor hypothesis").(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Vomeromodulin, a putative pheromone transporter: cloning, characterization, and cellular localization of a novel glycoprotein of lateral nasal gland.

Vomeromodulin, a novel glycoprotein of lateral nasal gland, has been cloned by differential hybridization from nasal/olfactory tissue. The 2.2-kb mRNA directs the in vitro synthesis of a 60-kDa primary translation product in reticulocyte lysates. Differential sensitivity to endoglycosidases indicates that vomeromodulin is posttranslationally modified in vivo by N-glycosylation to form a 70-kDa glycoprotein of the complex type. Immunocytochemical localization with two different antipeptide antisera demonstrates that vomeromodulin is abundant in the lateral nasal glands and is also present in the posterior septal and vomeronasal glands. Most striking is the observation that it is highly concentrated in the mucus of the vomeronasal organ of Jacobson but is not detectable in the mucus of the main olfactory neuroepithelium. Evaluation of mRNA and protein distribution by Northern and Western analyses, respectively, indicates that vomeromodulin is absent from 15 other tissues. The glandular and mucosal distribution of this glycoprotein implies a transport function that may be related to the mechanisms by which pheromones of low volatility gain access to their receptors in the vomeronasal organ. These observations support our hypothesis that vomeromodulin participates in perireceptor events that facilitate the process of pheromone access and detection.

Amino Acid Sequence↗
PubMed1991

Reverse genetics in the mouse and its application to the study of deafness.

Genetic variants of the laboratory mouse can serve as useful models for hereditary deafness syndromes in humans. Recessive mutations at the shaker-1 (sh-1) and whirler (wi) loci, in chromosomes 7 and 4, respectively, both result in circling behavior and a deafness syndrome. In sh-1 homozygotes this deafness is associated with neurophysiological abnormalities that may be accompanied by structural abnormalities of the inner ear. Radiation-induced deletion mutations are being used in a strategy of reverse genetics to identify the genes defined by these mutations. Genetic analyses have refined the position of sh-1 to a chromosomal interval between break points of deletions involving the closely linked albino (c) locus. A cDNA encoding olfactory marker protein (OMP) and the anonymous locus D7OR1 have also been mapped to this interval. These clones contribute to the physical map of the sh-1 region and could be important for accessing the sh-1 gene itself. Similarly, we have identified a radiation-induced deletion of the brown (b) locus that covers the wi locus and two that do not. Thus, the wi locus has been located within a chromosome 4 interval defined by structural rearrangements, which should likewise aid in identifying closely linked molecular clones.

Animals↗
PubMed1991

Distribution of carnosine-like immunoreactivity in the brain of the crested newt.

The distribution of the dipeptide carnosine was studied in the brain of the crested newt, Triturus carnifex, with immunohistochemical methods. Carnosine-like immunoreactivity (IR) is present in the cell bodies and processes of several areas of the central nervous system: in the telencephalon (especially in the medial pallium), in the diencephalon (pineal organ, thalamus, and hypothalamus), in the mesencephalon (optic tectum and tegmentum), and in the rhombencephalon (cerebellum, raphe region, and octavolateralis area). Double-labelling experiments show that carnosine IR is colocalized with tyrosine hydroxylase and neuropeptide Y IR in a few cells. Histochemical staining for heavy metals, the TIMM method, reveals that carnosine IR and TIMM labelling overlap in the medial pallium. These data indicate two primary conclusions: (a) In the crested newt brain, in contrast to those of mammals and birds, carnosine IR is not associated with glial cells but with neurons. Furthermore, carnosine is absent from the primary olfactory pathway in newts. (b) In the medial pallium of the crested newt, carnosine IR reliably identifies a population of neurons.

Animals↗
PubMed1990

Neuroplasticity in the olfactory system: differential effects of central and peripheral lesions of the primary olfactory pathway on the expression of B-50/GAP43 and the olfactory marker protein.

The regeneration of the olfactory neuroepithelium following olfactory bulbectomy or peripheral deafferentation was studied with mRNA probes and antibodies for B-50/GAP43 and for olfactory marker protein (OMP). Two stages in the regeneration of the olfactory epithelium could be discerned with these reagents. The first stage occurs following either peripheral deafferentation of the olfactory epithelium with Triton X-100 (TX-100) or after bulbectomy and is characterized by the formation of a large population of immature olfactory receptor neurons. These newly formed neurons express B-50/GAP43, a phosphoprotein related to neuronal growth and plasticity. During the second stage of the regeneration process the newly formed olfactory neurons mature, as evidenced by a decrease in their expression of B-50/GAP43 and an increase in the expression of OMP. This stage is only manifested if the developing neurons have access to the target olfactory bulb. Formation of a full complement of OMP-expressing neurons occurs only after peripheral lesion with TX-100. In contrast, following bulbectomy the reconstituted olfactory epithelium lacks its normal target and is compromised in its ability to recover from nerve damage, as evidenced by the presence of a large number of B-50/GAP43-expressing neurons up to 3 months after the lesion and its failure to establish a full complement of OMP-expressing neurons. These results demonstrate that the olfactory epithelium is capable of replacing its sensory neurons independently of the presence of its target, the olfactory bulb. However, the differential patterns of expression of B-50/GAP43 and OMP at long times after peripheral lesion with TX-100 or bulbectomy illustrate the profound effect the olfactory bulb has on neuronal maturation in reconstituted olfactory neuroepithelium.

Animals↗