Like most animals, insects rely on their olfactory systems for finding food and mates and in avoiding noxious chemicals and predators. Most insect olfactory neurons express an odorant-specific odorant receptor (OR) along with Orco, the olfactory co-receptor. Orco binds ORs and permits their trafficking to the dendrites of antennal olfactory sensory neurons (OSNs), where together, they are suggested to form heteromeric ligand-gated non-selective cation channels. While most amino acid residues in Orco are well conserved across insect orders, one especially well-conserved region in Orco’s second intracellular loop is a putative calmodulin (CaM) binding site (CBS). In this study, we explore the relationship between Orco and CaM in vivo in the olfactory neurons of Drosophila melanogaster.
We first found OSN-specific knock-down of CaM at the onset of OSN development disrupts the spontaneous firing of OSNs and reduces Orco trafficking to the ciliated dendrites of OSNs without affecting their morphology. We then generated a series of Orco CBS mutant proteins and found that none of them rescue the Orco-null Orco1 mutant phenotype, which is characterized by an OR protein trafficking defect that blocks spontaneous and odorant-evoked OSN activity. In contrast to an identically constructed wild-type form of Orco that does rescue the Orco1 phenotype, all the Orco CBS mutants remain stuck in the OSN soma, preventing even the smallest odorant-evoked response. Last, we found CaM’s modulation of OR trafficking is dependent on activity. Knock-down of CaM in all Orco-positive OSNs after OR expression is well established has little effect on olfactory responsiveness alone. When combined with an extended exposure to odorant, however, this late-onset CaM knock-down significantly reduces both olfactory sensitivity and the trafficking of Orco only to the ciliated dendrites of OSNs that respond to the exposed odorant.
In this study, we show CaM regulates OR trafficking and olfactory responses in vivo in Drosophila olfactory neurons via a well-conserved binding site on the olfactory co-receptor Orco. As CaM’s modulation of Orco seems to be dependent on activity, we propose a model in which the CaM/Orco interaction allows insect OSNs to maintain appropriate dendritic levels of OR regardless of environmental odorant concentrations.
Insect olfaction; Drosophila melanogaster; odorant receptor; Orco; calmodulin
The Drosophila olfactory system is highly stereotyped in form and function; olfactory sensory neurons (OSNs) expressing a specific odorant receptor (OR) always appear in the same antennal location and the axons of OSNs expressing the same OR converge on the same antennal lobe glomeruli. Although some transcription factors have been implicated in a combinatorial code specifying OR expression and OSN identity, it is clear other players remain unidentified. In hopes of mitigating the challenges of genome-wide screening, we examined the feasibility of a two-tiered approach comprising a primary “pooling” screen for miRNAs whose tissue-specific over-expression causes a phenotype of interest followed by a focused secondary screen using gene-specific RNAi. Since miRNAs down-regulate their targets, miRNA over-expression phenotypes should be attributable to target loss-of-function. It is the sequence-dependence of miRNA-target pairing that suggests candidates for the secondary screen. Since miRNAs are short, however, miRNA misexpression will likely uncover non-biological miRNA-target relationships. Rather than focusing on miRNA function itself where these non-biological relationships could be misleading, we propose using miRNAs as tools to focus a more traditional RNAi-based screen. Here we describe such a screen that uncovers a role for Atf3 in the expression of the odorant receptor Or47b.
Mammalian T-type Ca2+ channels are encoded by three separate genes (Cav3.1, 3.2, 3.3). These channels are reported to be sleep stabilizers important in the generation of the delta rhythms of deep sleep, but controversy remains. The identification of precise physiological functions for the T-type channels has been hindered, at least in part, by the potential for compensation between the products of these three genes and a lack of specific pharmacological inhibitors. Invertebrates have only one T-type channel gene, but its functions are even less well-studied. We cloned Ca-α1T, the only Cav3 channel gene in Drosophila melanogaster, expressed it in Xenopus oocytes and HEK-293 cells, and confirmed it passes typical T-type currents. Voltage-clamp analysis revealed the biophysical properties of Ca-α1T show mixed similarity, sometimes falling closer to Cav3.1, sometimes to Cav3.2, and sometimes to Cav3.3. We found Ca-α1T is broadly expressed across the adult fly brain in a pattern vaguely reminiscent of mammalian T-type channels. In addition, flies lacking Ca-α1T show an abnormal increase in sleep duration most pronounced during subjective day under continuous dark conditions despite normal oscillations of the circadian clock. Thus, our study suggests invertebrate T-type Ca2+ channels promote wakefulness rather than stabilizing sleep.
MicroRNAs (miRNAs) regulate many physiological processes including body growth. Insulin/IGF signalling is the primary regulator of animal body growth, but the extent to which miRNAs act in insulin-producing cells (IPCs) is unclear. Here we generate a UAS-miRNA library of Drosophila stocks and perform a genetic screen to identify miRNAs whose overexpression in the IPCs inhibits body growth in Drosophila. Through this screen, we identify miR-9a as an evolutionarily conserved regulator of insulin signalling and body growth. IPC-specific miR-9a overexpression reduces insulin signalling and body size. Of the predicted targets of miR-9a, we find that loss of miR-9a enhances the level of sNPFR1. We show via an in vitro binding assay that miR-9a binds to sNPFR1 mRNA in insect cells and to the mammalian orthologue NPY2R in rat insulinoma cells. These findings indicate that the conserved miR-9a regulates body growth by controlling sNPFR1/NPYR-mediated modulation of insulin signalling.
Insulin signaling governs many physiological processes but the molecular and neural mechanisms of its regulation are largely unknown. Here the authors describe a novel molecular pathway controlling sNPF regulation of insulin signalling in the fruit fly, which is mediated by the evolutionary conserved miR-9a.
Chromatin diminution is the programmed deletion of DNA from presomatic cell or nuclear lineages during development, producing single organisms that contain two different nuclear genomes. Phylogenetically diverse taxa undergo chromatin diminution — some ciliates, nematodes, copepods, and vertebrates. In cyclopoid copepods, chromatin diminution occurs in taxa with massively expanded germline genomes; depending on species, germline genome sizes range from 15 – 75 Gb, 12–74 Gb of which are lost from pre-somatic cell lineages at germline – soma differentiation. This is more than an order of magnitude more sequence than is lost from other taxa. To date, the sequences excised from copepods have not been analyzed using large-scale genomic datasets, and the processes underlying germline genomic gigantism in this clade, as well as the functional significance of chromatin diminution, have remained unknown.
Here, we used high-throughput genomic sequencing and qPCR to characterize the germline and somatic genomes of Mesocyclops edax, a freshwater cyclopoid copepod with a germline genome of ~15 Gb and a somatic genome of ~3 Gb. We show that most of the excised DNA consists of repetitive sequences that are either 1) verifiable transposable elements (TEs), or 2) non-simple repeats of likely TE origin. Repeat elements in both genomes are skewed towards younger (i.e. less divergent) elements. Excised DNA is a non-random sample of the germline repeat element landscape; younger elements, and high frequency DNA transposons and LINEs, are disproportionately eliminated from the somatic genome.
Our results suggest that germline genome expansion in M. edax reflects explosive repeat element proliferation, and that billions of base pairs of such repeats are deleted from the somatic genome every generation. Thus, we hypothesize that chromatin diminution is a mechanism that controls repeat element load, and that this load can evolve to be divergent between tissue types within single organisms.
Chromatin diminution; Genome size; Transposable elements; Germline-soma differentiation; Copepod
The proto-oncogenic protein c-Myb is an essential regulator of hematopoiesis and is frequently deregulated in hematological diseases such as lymphoma and leukemia. To gain insight into the mechanisms underlying the aberrant expression of c-Myb in myeloid leukemia, we analyzed and compared c-myb gene transcriptional regulation using two cell lines modeling normal hematopoietic progenitor cells (HPCs) and transformed myelomonocytic blasts. We report that the transcription factors HoxA9, Meis1, Pbx1 and Pbx2 bind in vivo to the c-myb locus and maintain its expression through different mechanisms in HPCs and leukemic cells. Our analysis also points to a critical role for Pbx2 in deregulating c-myb expression in murine myeloid cells cotransformed by the cooperative activity of HoxA9 and Meis1. This effect is associated with an intronic positioning of epigenetic marks and RNA polymerase II binding in the orthologous region of a previously described alternative promoter for c-myb. Taken together, our results could provide a first hint to explain the abnormal expression of c-myb in leukemic cells.
c-myb; hematopoietic progenitors; myeloid leukemia; Hox and TALE proteins
Animal populations act as reservoirs for emerging diseases. In order for transmission to be self-sustaining, a pathogen must have a basic reproduction number R0 > 1. Following a founding transmission event from an animal reservoir to humans, a pathogen has not yet adapted to its new environment and is likely to have an R0 < 1. However, subsequent evolution may rescue the pathogen from extinction in its new host. Recent applications of branching process theory investigate how the emergence of a novel pathogen is influenced by the number and rates of intermediate evolutionary steps. In addition, repeated contacts between human and reservoir populations may promote pathogen emergence. This article extends a stepping-stone model of pathogen evolution to include reservoir interactions. We demonstrate that the probability of a founding event culminating in an emerged pathogen can be significantly influenced by ongoing reservoir interactions. While infrequent reservoir interactions do not change the probability of disease emergence, moderately frequent interactions can promote emergence by facilitating adaptation to humans. Frequent reservoir interactions promote emergence even with minimal adaptation to humans. Thus, these results warn against perpetuated interaction between humans and animal reservoirs, as occurs when there are ecological or environmental changes that bring humans into more frequent contact with animal reservoirs.
reservoirs; infectious diseases; branching processes; zoonosis; emergence
Advances in molecular typing of fusariosis would facilitate the study of its epidemiology. We tested 26 such isolates by the commercially available DiversiLab System. The system utilizes automated repetitive sequence-based PCR (rep-PCR) and web-based data analyses. rep-PCR dendrogram cluster analysis showed agreement with species sequence identification (elongation factor 1 alpha gene). Additionally, subtype differences within the same species were noted.
A commercially available repetitive-sequence-based PCR (rep-PCR) DNA fingerprinting assay adapted to an automated format, the DiversiLab system, enables rapid microbial identification and strain typing. We explored the performance of the DiversiLab system as a molecular typing tool for 69 Aspergillus isolates (38 A. fumigatus, 15 A. flavus, and 16 A. terreus isolates) had been previously characterized by morphological analysis. Initially, 27 Aspergillus isolates (10 A. fumigatus, 9 A. flavus, and 8 A. terreus isolates) were used as controls to create a rep-PCR-based DNA fingerprint library with the DiversiLab software. Then, 42 blinded Aspergillus isolates were typed using the system. The rep-PCR-based profile revealed 98% concordance with morphology-based identification. rep-PCR-based DNA fingerprints were reproducible and were consistent for DNA from both hyphae and conidia. DiversiLab dendrogram reports correctly identified all A. fumigatus (n = 28), A. terreus (n = 8), and A. flavus (n = 6) isolates in the 42 blinded Aspergillus isolates. rep-PCR-based identification of all isolates was 100% in agreement with the contiguous internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) sequence-based identification of the respective isolates. Additionally, the DiversiLab system could demonstrate strain-level differentiation of A. flavus and A. terreus. Automated rep-PCR may be a time-efficient, effective, easy-to-use, novel genotyping tool for identifying and determining the strain relatedness of fungi. This system may be useful for epidemiological studies, molecular typing, and surveillance of Aspergillus species.
Interleukin 6 (IL-6) is secreted by breast tumours and shows synergistic activity with 17β-oestradiol (E2), leading to increases in reductive 17β-hydroxysteroid dehydrogenase activity in breast cancer epithelial cells. However, the mechanisms involved are poorly understood. Using short-term epithelial cultures established from primary breast tumours, we have examined whether IL-6 could directly affect transcriptional activity of oestrogen reception α (ERα). Tumour epithelial cultures were established from 15 breast tumours, grown to 70% confluence and transiently transfected with a plasmid reporter containing the vitellogenin oestrogen response element and the luciferase coding sequence (ERE-TK-LUC). Following transfection, cells were incubated with E2, IL-6, the pure anti-oestrogen ZM 182780 or combinations of these substances for 48 h. Luciferase activity was then measured in cell lysates. E2 caused a dose-dependent increase in luciferase expression, causing a maximum threefold stimulation at 100 p M. In the presence of IL-6, transcriptional activity was increased by up to 2.5-fold in ERα+cultures (11/15). In combination with E2, synergistic effects were observed with increases in luciferase activity of up to sixfold over controls. This effect could be blocked by treatment with ZM 182780. Pre-incubation of cells with an antibody directed against the signalling component of IL-6, gp130, was ineffective in blocking the E2 response. This antibody reduced, but did not completely block the effect of IL-6 either alone or in combination with E2, suggesting cross-talk between the two signalling pathways. In conclusion, these results provide evidence for direct transcriptional activation of ERα by IL-6. © 2000 Cancer Research Campaign
Enzymes modulating local steroid availability play an important role in the progression of human breast cancer. These include isoforms of 17β-hydroxysteroid dehydrogenase (17-HSD), aromatase and steroid sulphatase (STS). The aim of this study was to investigate the expression, by reverse transcription polymerase chain reaction, of 17-HSD types I–IV, aromatase and steroid STS in a series of 51 human breast tumour biopsies and 22 primary cultures of epithelial and stromal cells derived from these tumours, giving a profile of the steroid-regulating network for individual tumours. Correlations between enzyme expression profiles and expression of the interleukin (IL)-6 gene were also sought. All except one tumour expressed at least one isoform of 17-HSD, either alone or in combination with aromatase and STS. Expression of 17-HSD isoforms I–IV were observed in nine tumours. Of the 15 tumours which expressed three isoforms, a combination of 17-HSD II, III and IV was most common (6/15 samples). The majority of tumours (n = 17) expressed two isoforms of 17-HSD with combinations of 17-HSD II and IV predominant (7/17 samples). Eight tumours expressed a single isoform and of these, 17-HSD I was in the majority (5/8 samples). In primary epithelial cultures, enzyme expression was ranked: HSD I (86%) > STS (77%) > HSD II (59%) > HSD IV (50%) = aromatase (50%) > HSD III (32%). Incidence of enzyme expression was generally reduced in stromal cultures which were ranked: HSD I (68%) > STS (67%) > aromatase (48%) > HSD II (43%) > HSD IV (28%) > HSD III (19%). Expression of IL-6 was associated with tumours that expressed ≥ 3 steroid-converting enzymes. These tumours were of higher grade and tended to come from patients with family history of breast cancer. In conclusion, we propose that these enzymes work in tandem with cytokines thereby providing sufficient quantities of bioactive oestrogen from less active precursors which stimulates tumour growth. © 1999 Cancer Research Campaign
breast cancer; steroids; interleukin-6
As experimental models for breast cancer, most studies rely on established human breast cancer cell lines. However, many of these lines were established over 20 years ago, many from pleural effusions rather than the primary tumour, so the validity of using them as representative models is questionable. This paper describes our experiences, over a 3-year period, in establishing short-term epithelial-cell-enriched preparations from primary breast tumours based on differential centrifugation followed by culture in selective media. Epithelial cells were successfully cultured from 55% of samples, but culture success did not appear to be correlated with tumour histology, stage, grade or node status. Epithelial cell-enriched cultures were immunopositive for broad-spectrum cytokeratin and epithelial membrane antigen (EMA). Positivity for keratin 19 confirmed that the cultures contained tumour-derived cells, which additionally showed significantly higher activity of the reductive pathway of the steroid-converting enzyme 17beta-hydroxysteroid dehydrogenase type I. That the cultures contained tumour and not normal epithelial cells was further substantiated by the complete absence of the calmodulin-like gene NB-1 in tumour-derived cultures; this is only associated with normal breast epithelia. Eighty-five per cent of cultures established from oestrogen receptor (ER)-positive tumours expressed ER in vitro; this was functional in 66% of cultures, although ER-positive phenotype was gradually lost over time. In conclusion, epithelial cells can be isolated and maintained as short-term cultures from primary breast tumours irrespective of histopathological or clinical details, providing a model system with a greater biological and clinical relevance than breast cancer cell lines.
PURPOSE: We conducted a retrospective study to report the long-term success and complications of modified goniosurgery to prevent aniridic glaucoma, an entity that typically is difficult to control medically or surgically. METHODS: Fifty-five eyes in 33 patients who had aniridia without glaucoma and who had goniosurgery were identified. Ninety-one procedures were performed on 55 eyes by 1 surgeon (D.S.W.). Each eye had an average of 1.65 procedures and an average of 200 degrees of goniosurgery. Average patient age at time of initial goniosurgery was 37 months. There were no operative complications. RESULTS: No eye had a decrease in visual acuity at last follow-up. All eyes had a preoperative intraocular pressure (IOP) of less than 21 mm Hg. At last follow-up (average, 9 years 6 months; range, 8 months to 24 years), 49 eyes (89%) had IOP of less than 22 mm Hg without medications. The remaining 6 eyes (11%) had IOP of less than or equal to 22 mm Hg with up to 2 eye drops. Of 224 aniridic eyes of 112 patients that were seen for eye care by 1 of the authors (D.S.W.), 119 eyes (53%) demonstrated glaucoma, as defined by IOP of greater than 21 mm Hg. CONCLUSIONS: Without prophylactic goniotomy, aniridic glaucoma may be expected in half of patients, and when it occurs, it is extremely difficult to control. Prophylactic goniosurgery in selected eyes of young patients with aniridia is effective in preventing aniridic glaucoma.
PURPOSE: To determine the effect of peripheral retinal laser photocoagulation (PLP) on visual acuity, intraocular inflammation, and other ocular findings, including retinal neovascularization in eyes with pars planitis. METHODS: A retrospective chart review of eyes with pars planitis that had undergone PLP. RESULTS: Twenty-two eyes in 17 patients with pars planitis had undergone treatment with PLP at 2 centers. The mean age at the time of treatment was 19.3 years. Following treatment, mean follow-up was 16.3 months (range, 6 to 37 months). Mean visual acuity was 20/60 preoperatively and 20/50 postoperatively. This level of improvement was not statistically significant (P > .10), but there was a statistically significant decrease in the use of corticosteroids between the preoperative examination and the last postoperative examination (86% versus 27%, P < .05). There was also a statistically significant decrease in vitritis at the last follow-up (P = .0008) and a decrease in neovascularization of the vitreous base (P = .03) and in clinically apparent cystoid macular edema (P = .02). Epiretinal membranes were noted in 23% of eyes preoperatively and in 45% of eyes postoperatively. Only one of these epiretinal membranes was considered to be visually significant. One eye developed a tonic dilated pupil, which slowly improved. CONCLUSIONS: Although the long-term natural history of clinical findings in pars planitis is not well documented, PLP appears to decrease the need for corticosteroids while stabilizing visual acuity. It also appears to decrease vitreous inflammation. PLP has few complications and should be considered in patients with pars planitis who are unresponsive or have adverse reactions to corticosteroids.
PURPOSE: The anterior segment findings of children with glaucoma following pediatric cataract extraction were studied to determine the mechanism of this complication. METHODS: The clinical records of 65 children with glaucoma cared for by the author were studied. Patients with bilateral lensectomy followed by bilateral glaucoma, bilateral lensectomy followed by unilateral glaucoma, and unilateral lens surgery followed by glaucoma were identified and studied. RESULTS: It was determined that vitreous cutting instruments were used for 80% of the lensectomy procedures, with 77% of the lens procedures done in the first year. Eighty-seven percent of the patients were recognized to have glaucoma two or more years after their lensectomy. Preoperative gonioscopy revealed no consistent angle defect, while postoperative gonioscopy revealed a near constant (96%) but variable angle defect characterized by blockage of the trabecular meshwork by an acquired repositioning of the iris against the posterior trabecular meshwork, associated with abnormal pigmentation and synechia formation. CONCLUSION: The results reported document the development of a characteristic acquired filtration angle deformity in children with glaucoma following early lensectomy frequently associated with significant residual lens tissue and unassociated with evidence of chronic anterior segment inflammation.
An unusual strain of Edwardsiella tarda mimicking a biogroup 1 isolate was recovered in a mixed infection from a woman suffering from cholelithiasis. Rare biochemical characteristics (e.g., H2S negativity) originally detected were related to an unusual biochemical property in this species, sucrose fermentation; other points of interest regarding this strain included the site of isolation (bile) and the failure of this isolate to produce many of the in vitro virulence markers associated with E. tarda.
The Mycobacterium gordonae Rapid Diagnostic System (Gen-Probe, Inc., San Diego, Calif.) was evaluated for sensitivity and specificity as well as for its application in the mycobacteriology laboratory. An 125I-labeled cDNA probe complementary to rRNA was employed. Hybridization of greater than or equal to 10% was considered positive. A total of 218 mycobacterial isolates, including 159 isolates of M. gordonae, were tested. Under optimum conditions, the specificity and sensitivity of the probe were 100 and 98.7%, respectively. A number of discrepancies were observed between the probe and conventional biochemical results in one laboratory. Further studies, designed to resolve these discrepancies, revealed a number of potential technical pitfalls. Hybridization incubation temperatures that varied from the manufacturer's recommended optimum, culture suspensions below the density of a no. 1 McFarland nephelometer standard, and extended storage times of culture suspension all adversely affected the final hybridization values. Additionally, it was determined that in one laboratory incorrect functioning of the sonicator caused false-negative hybridization values. The manufacturer's recommendations should be strictly followed, and the performance of the sonicator should be checked on a scheduled basis. Results show that the probe will allow fast and accurate identification of M. gordonae, thus eliminating time-consuming biochemical testing of this organism.
The incidence of monoclonal-fluorescent-antibody-negative penicillinase-producing Neisseria gonorrhoeae is not known. Two isolates which could not be identified by using a commercial monoclonal fluorescent-antibody conjugate are described. The use of more than one confirmatory method is recommended.
A 5-day-old female patient was found to have large hereditary retinoblastomas in the posterior pole of each eye. The patient received radiation treatment over a 39-day period, with each retina receiving 4600 rad. Two weeks after the complete treatment the tumours had regressed to approximately one-quarter of their original size. By 14 weeks following completion of radiotherapy the patient had developed in each eye extensive iris neovascularisation with progressive closure of the filtration angles, secondary glaucoma, and retinal detachments resulting from fibrovascular proliferation on the retinal surface. Radiosensitivity studies were from separate conjunctival biopsies obtained before and after radiation. These showed a D0 (calculated survival curve parameters, defined in the Methods section) in the exponential growth phase of 110 prior to radiation and a postirradiation exponential growth phase D0 of 70. Karotype studies showed several chromosomal abnormalities following radiotherapy. The clinical course and pathology findings are thought to represent an unusually severe orbital and ocular response to radiation therapy. These findings are consistent with our hypothesis that some patients with hereditary retinoblastoma may have a defect in the accumulation repair of x-irradiation induced DNA damage.
Repetitive gonioscopy of children with congenital aniridia confirms the presence of an angle abnormality which can be progressive and cause glaucoma. This abnormality features obstruction of the trabecular meshwork by variable mixtures of anterior migration of the peripheral iris and thickening of the uveal meshwork associated with a vascular net over exposed trabecular meshwork adjacent to the anterior edge of the iris. Preliminary results of prophylactic gonio-surgery in 28 eyes of 16 children with an average age of 4 years was reported. This surgery was performed without complication and produced a permanent exposure of the trabecular meshwork to the anterior chamber for an average of 8 circumferential hours, if two procedures were performed. Preliminary results suggest a stabilization of eye pressures at least through childhood and encourage the continuation of these prophylactic operations on selected eyes with congenital aniridia. Therapeutic goniotomy for established acquired glaucoma in congenital aniridia cannot be relied on, but may be a benefit for early detected cases or for glaucoma associated with aniridia in infancy.