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J R Carlson

Publications and source records attributed to J R Carlson.

At least 19 recordsLinked to original sources
PubMed2002

Inactivation of olfactory sensilla of a single morphological type differentially affects the response of Drosophila to odors.

The olfactory organs on the head of Drosophila, antennae and maxillary palps, contain several hundred olfactory hairs, each with one or more olfactory receptor neurons. Olfactory hairs belong to one of three main morphological types, trichoid, basiconic, and coeloconic sensilla, and show characteristic spatial distribution patterns on the surface of the antenna and maxillary palps. Here we show that targeting expression of the cell-death gene reaper to basiconic sensilla (BS) causes the specific inactivation of most olfactory sensilla of this type with no detectable effect on other types of olfactory sensilla or the structure of the antennal lobe. Our data suggest that BS are required for a normal sensitivity to many odorants with a variety of chemical structures, through a wide range of concentrations. Interestingly, however, in contrast to other odorants tested, the behavioral response of ablated flies to intermediate concentrations of propionic and butyric acids is normal, suggesting the involvement of sensilla unaffected by ectopic reaper expression, probably coeloconic sensilla that respond strongly to these two organic acids. As inactivation of BS causes an underestimation of the concentration of both acids detectable at both the highest and lowest odorants concentrations, our results suggest that concentration coding for these two odorants relies on the integration of signals from different subsets of sensilla, most likely of different morphological types.

Animals↗
PubMed2002

Visual arrestins in olfactory pathways of Drosophila and the malaria vector mosquito Anopheles gambiae.

Arrestins are important components for desensitization of G protein-coupled receptor cascades that mediate neurotransmission as well as olfactory and visual sensory reception. We have isolated AgArr1, an arrestin-encoding cDNA from the malaria vector mosquito, Anopheles gambiae, where olfaction is critical for vectorial capacity. Analysis of AgArr1 expression revealed an overlap between chemosensory and photoreceptor neurons. Furthermore, an examination of previously identified arrestins from Drosophila melanogaster exposed similar bimodal expression, and Drosophila arrestin mutants demonstrate impaired electrophysiological responses to olfactory stimuli. Thus, we show that arrestins in Drosophila are required for normal olfactory physiology in addition to their previously described role in visual signaling. These findings suggest that individual arrestins function in both olfactory and visual pathways in Dipteran insects; these genes may prove useful in the design of control strategies that target olfactory-dependent behaviors of insect disease vectors.

Amino Acid Sequence↗
PubMed2001

Expression mosaic of odorant-binding proteins in Drosophila olfactory organs.

Deciphering the genome of the fruitfly, Drosophila melanogaster, has revealed 39 genes coding for putative odorant-binding proteins (OBPs), more than are known at present for any other insect species. Using specific antibodies, the expression mosaic of five such OBPs (OS-E, OS-F, LUSH, PBPRP2, PBPRP5) on the antenna and maxillary palp has been mapped in the electron microscope. It was found that (1) OBP expression does correlate with morphological sensillum types and subtypes, (2) several OBPs may be co-localized in the same sensillum, and (3) OBP localization is not restricted to olfactory sensilla. The expression of PBPRP2 in antennal epidermis sheds some light on the possible evolution of OBPs.

Animals↗
PubMed2001

Candidate odorant receptors from the malaria vector mosquito Anopheles gambiae and evidence of down-regulation in response to blood feeding.

Olfaction plays a major role in host preference and blood feeding, integral behaviors for disease transmission by the malaria vector mosquito Anopheles gambiae sensu stricto (henceforth A. gambiae). We have identified four genes encoding candidate odorant receptors from A. gambiae that are selectively expressed in olfactory organs, contain approximately seven transmembrane domains, and show significant similarity to several putative odorant receptors in Drosophila melanogaster. Furthermore, one of the putative A. gambiae odorant receptors exhibits female-specific antennal expression and is down-regulated 12 h after blood feeding, a period during which substantial reduction in olfactory responses to human odorants has been observed. Taken together, these data suggest these genes encode a family of odorant receptors in A. gambiae, whose further study may aid in the design of novel antimalarial programs.

Amino Acid Sequence↗
PubMed2001

Control of Drosophila perineurial glial growth by interacting neurotransmitter-mediated signaling pathways.

Drosophila peripheral nerves, similar structurally to the peripheral nerves of mammals, comprise a layer of axons and inner glia, surrounded by an outer perineurial glial layer. Although it is well established that intercellular communication occurs among cells within peripheral nerves, the signaling pathways used and the effects of this signaling on nerve structure and function remain incompletely understood. Here we demonstrate with genetic methods that the Drosophila peripheral nerve is a favorable system for the study of intercellular signaling. We show that growth of the perineurial glia is controlled by interactions among five genes: ine, which encodes a putative neurotransmitter transporter; eag, which encodes a potassium channel; push, which encodes a large, Zn(2+)-finger-containing protein; amn, which encodes a putative neuropeptide related to the pituitary adenylate cyclase activator peptide; and NF1, the Drosophila ortholog of the human gene responsible for type 1 neurofibromatosis. In other Drosophila systems, push and NF1 are required for signaling pathways mediated by Amn or the pituitary adenylate cyclase activator peptide. Our results support a model in which the Amn neuropeptide, acting through Push and NF1, inhibits perineurial glial growth, whereas the substrate neurotransmitter of Ine promotes perineurial glial growth. Defective intercellular signaling within peripheral nerves might underlie the formation of neurofibromas, the hallmark of neurofibromatosis.

Animals↗
PubMed2001

Viewing odors in the mushroom body of the fly.

Central processing of olfactory information has been analyzed in the mushroom body of Drosophila by Ca(2+) imaging, extending such analysis of odor coding to the second relay of the olfactory system. Different odors, and different concentrations of a particular odor, yield distinct spatial patterns of activity. Mutations that affect odor receptors and odorant-binding proteins affect these spatial patterns.

Animals↗
PubMed2001

Odor coding in the Drosophila antenna.

Odor coding in the Drosophila antenna is examined by a functional analysis of individual olfactory receptor neurons (ORNs) in vivo. Sixteen distinct classes of ORNs, each with a unique response spectrum to a panel of 47 diverse odors, are identified by extracellular recordings. ORNs exhibit multiple modes of response dynamics: an individual neuron can show either excitatory or inhibitory responses, and can exhibit different modes of termination kinetics, when stimulated with different odors. The 16 ORN classes are combined in stereotyped configurations within seven functional types of basiconic sensilla. One sensillum type contains four ORNs and the others contain two neurons, combined according to a strict pairing rule. We provide a functional map of ORNs, showing that each ORN class is restricted to a particular spatial domain on the antennal surface.

Action Potentials↗
PubMed2001

A Gr receptor is required for response to the sugar trehalose in taste neurons of Drosophila.

We recently identified from the Drosophila genome database a large family of G protein-coupled receptor genes, the Gr genes, and predicted that they encode taste receptors on the basis of their structure and specificity of expression. The expression of Gr genes in gustatory neurons has subsequently been confirmed and 56 family members have been reported. Here we provide functional evidence that one Gr gene, Gr5a, encodes a taste receptor required for response to the sugar trehalose. In two different mutants that carry deletions in Gr5a, electrophysiological and behavioral responses to trehalose were diminished but the response to sucrose was unaffected. Transgenic rescue experiments showed that Gr5a confers response to trehalose. The results correlate a particular taste ligand with a Gr receptor and indicate a role for G protein-mediated signaling in the transduction of sweet taste in Drosophila.

Action Potentials↗
PubMed2001

Olfaction in Drosophila: coding, genetics and e-genetics.

Odor coding in Drosophila is examined at both the cellular and molecular levels. Functional analysis of individual olfactory receptor neurons (ORNs) by single-unit electrophysiology has shown that ORNs divide into discrete classes, with each class exhibiting a characteristic odor response spectrum. Extensive analysis of ORNs in the maxillary palp has revealed six such classes, which are combined in sensilla according to a strict pairing rule. In order to identify the odor receptor genes that determine the odor specificity of these ORN classes, a new algorithm was designed to search DNA databases for proteins with a particular structure, as opposed to a particular sequence. The algorithm identified a large family of genes likely to encode odor receptors. The acj6 gene, originally identified in a screen for mutants defective in olfactory behavior, encodes a transcription factor that regulates a subset of these receptor genes, and is likely to play a critical role in the process by which ORNs select which receptors to express.

Algorithms↗
PubMed2001

Isolation of a deet-insensitive mutant of Drosophila melanogaster (Diptera: Drosophilidae).

Despite the widespread use of N,N,-diethyl-3-methylbenzamide (deet) in insect repellent products, nothing is known about the molecular basis for the repellency of deet, we initiated a molecular genetics program to elucidate the molecular mechanism of deet repellency in Drosophila melanogaster (Meigen). Deet repellency was apparently due to airborne vapors, as wild type flies were repelled by a deet-treated surface in the absence of physical contact and in the dark. A mutant was isolated using chemical mutagenesis and at choice assay. In a choice assay, mutant flies entered 82 +/- 1% of deet-containing tubes, whereas wild type flies entered only 6 +/- 2% of deet-containing tubes. The mutant was repelled by other repellents, benzaldehyde and citronellal. The mutation was recessive and located on the X chromosome.

Animals↗
PubMed2000

Candidate taste receptors in Drosophila.

Little is known about the molecular mechanisms of taste perception in animals, particularly the initial events of taste signaling. A large and diverse family of seven transmembrane domain proteins was identified from the Drosophila genome database with a computer algorithm that identifies proteins on the basis of structure. Eighteen of 19 genes examined were expressed in the Drosophila labellum, a gustatory organ of the proboscis. Expression was not detected in a variety of other tissues. The genes were not expressed in the labellum of a Drosophila mutant, pox-neuro70, in which taste neurons are eliminated. Tissue specificity of expression of these genes, along with their structural similarity, supports the possibility that the family encodes a large and divergent family of taste receptors.

Algorithms↗
PubMed2000

Identification of novel multi-transmembrane proteins from genomic databases using quasi-periodic structural properties.

MOTIVATION: Identification of novel G protein-coupled receptors and other multi-transmembrane proteins from genomic databases using structural features. RESULTS: Here we describe a new algorithm for identifying multi-transmembrane proteins from genomic databases with a specific application to identifying G protein-coupled receptors (GPCRs) that we call quasi-periodic feature classifier (QFC). The QFC algorithm uses concise statistical variables as the 'feature space' to characterize the quasi-periodic physico-chemical properties of multi-transmembrane proteins. For the case of identifying GPCRs, the variables are then used in a non-parametric linear discriminant function to separate GPCRs from non-GPCRs. The algorithm runs in time linearly proportional to the number of sequences, and performance on a test dataset shows 96% positive identification of known GPCRs. The QFC algorithm also works well with short random segments of proteins and it positively identified GPCRs at a level greater than 90% even with segments as short as 100 amino acids. The primary advantage of the algorithm is that it does not directly use primary sequence patterns which may be subject to sampling bias. The utility of the new algorithm has been demonstrated by the isolation from the Drosophila genome project database of a novel class of seven-transmembrane proteins which were shown to be the elusive olfactory receptor genes of Drosophila.

Algorithms↗
PubMed2000

quick-to-court, a Drosophila mutant with elevated levels of sexual behavior, is defective in a predicted coiled-coil protein.

Remarkably little is known about the molecular mechanisms that drive sexual behavior. We have identified a new gene, quick-to-court (qtc), whose mutations cause males to show high levels of male-male courtship. qtc males also show a novel phenotype: when placed in the presence of a virgin female, they begin courtship abnormally quickly. qtc mutations are striking in their specificity, in that many aspects of male sexual behavior are normal. We have cloned the qtc gene and found that it encodes a predicted coiled-coil protein and is expressed in the olfactory organs, central nervous system, and male reproductive tract.

Amino Acid Sequence↗
PubMed2000

Molecular evolution of odorant-binding protein genes OS-E and OS-F in Drosophila.

The Drosophila olfactory genes OS-E and OS-F are members of a family of genes that encode insect odorant-binding proteins (OBPs). OBPs are believed to transport hydrophobic odorants through the aqueous fluid within olfactory sensilla to the underlying receptor proteins. The recent discovery of a large family of olfactory receptor genes in Drosophila raises new questions about the function, diversity, regulation, and evolution of the OBP family. We have investigated the OS-E and OS-F genes in a variety of Drosophila species. These studies highlight potential regions of functional significance in the OS-E and OS-F proteins, which may include a region required for interaction with receptor proteins. Our results suggest that the two genes arose by an ancient gene duplication, and that in some lineages, one or the other gene has been lost. In D. virilis, the OS-F gene shows a different spatial pattern of expression than in D. melanogaster. One of the OS-F introns shows a striking degree of conservation between the two species, and we identify a putative regulatory sequence within this intron. Finally, a phylogenetic analysis places both OS-E and OS-F within a large family of insect OBPs and OBP-like proteins.

Amino Acid Sequence↗
PubMed2000

Regulation of central neuron synaptic targeting by the Drosophila POU protein, Acj6.

Mutations in the Drosophila class IV POU domain gene, abnormal chemosensory jump 6 (acj6), have previously been shown to cause physiological deficits in odor sensitivity. However, loss of Acj6 function also has a severe detrimental effect upon coordinated larval and adult movement that cannot be explained by the simple loss in odorant detection. In addition to olfactory sensory neurons, Acj6 is expressed in a distinct subset of postmitotic interneurons in the central nervous system from late embryonic to adult stages. In the larval and adult brain, Acj6 is highly expressed in central brain, optic and antennal lobe neurons. Loss of Acj6 function in larval optic lobe neurons results in disorganized retinal axon targeting and synapse selection. Furthermore, the lamina neurons themselves exhibit disorganized synaptic arbors in the medulla of acj6 mutant pupal brains, suggesting that Acj6 may play a role in regulating synaptic connections or structure. To further test this hypothesis, we misexpressed two Acj6 isoforms in motor neurons where they are not normally found. The two Acj6 isoforms are produced from alternatively spliced acj6 transcripts, resulting in significant structural differences in the amino-terminal POU IV box. Acj6 misexpression caused marked alterations at the neuromuscular junction, with contrasting effects upon nerve terminal branching and synapse formation associated with specific Acj6 isoforms. Our results suggest that the class IV POU domain factor, Acj6, may play an important role in regulating synaptic target selection by central neurons and that the amino-terminal POU IV box is important for regulation of Acj6 activity.

Alternative Splicing↗
PubMed2000

Chondroblastoma of bone.

BACKGROUND: Chondroblastoma of bone is a rare lesion, and few large series have been reported. The purpose of this paper is to report forty-seven cases treated by one group of surgeons and to identify factors associated with more aggressive tumor behavior. METHODS: Seventy-three patients with chondroblastoma of bone were treated between 1977 and 1998. We were able to obtain historical data, imaging studies, histological findings, and adequate personal or telephone follow-up to determine the outcome for forty-seven patients. RESULTS: The lesions were distributed widely in the skeleton, but most were in the epiphyses or apophyses of the long bones, especially the proximal part of the tibia (eleven tumors) and the proximal part of the humerus (ten tumors). The principal presenting symptoms were pain and limitation of movement. The treatment consisted of a variety of procedures, but the majority of the patients had intralesional curettage and packing with allograft or autograft bone chips or polymethylmethacrylate. Most of the patients had an excellent functional result, although in three osteoarthritis developed in the adjacent joint. Seven patients (15 percent) had a local recurrence; three of them had a second recurrence and one, a third recurrence. One patient died of widespread metastases, and another who had metastases to multiple sites was alive and disease-free after aggressive treatment of the metastatic lesions. CONCLUSIONS: While the size of the lesion, the age and gender of the patient, the status of the growth plate, and an aneurysmal-bone-cyst component to the tumor had no significant effect on the recurrence rate, lesions around the hip (the proximal part of the femur, the greater trochanter, and the pelvis) accounted for the majority (five) of the seven recurrent tumors and one of the two metastatic lesions.

Adolescent↗