Characterization of olfactory genes in the antennae of the Southern house mosquito, Culex quinquefasciatus

Odorant reception in insects is mediated by different families of olfactory proteins. Here we focus on the characterization of odorant-binding proteins (OBPs), "plus-C" odorant-binding proteins ("plus-C" OBPs), chemosensory proteins (CSPs) and sensory neuron membrane proteins (SNMPs) families from the Southern house mosquito, Culex quinquefasciatus, a vector of pathogens implicated in multiple human diseases. Using bioinformatics and molecular approaches, we have identified a diversity of genes in the genome of Culex quinquefasciatus and examined their expression profiles by RT-PCR and real-time quantitative PCR. Based on their high transcript enrichment in female antennae compared to non-olfactory tissues, we have identified twelve OBPs, two "plus-C" OBPs and two SNMPs that likely play important roles in odorant reception. Transcripts of two genes were clearly enriched in female antennae compared to male antennae, whereas other genes displayed relatively equivalent transcript levels in antennae of both sexes. Additionally, eight genes were found to be transcribed at very high levels in female antennae compared to CquiOR7, suggesting they might encode highly abundant olfactory proteins. Comparative analysis across different mosquito species revealed that olfactory genes of Culex quinquefasciatus are related to putative orthologs in other species, indicating that they might perform similar functions. Understanding how mosquitoes are able to detect ecologically relevant odorant cues might help designing better control strategies. We have identified olfactory genes from different families which are likely important in Culex quinquefasciatus behaviors, thus paving the way towards a better understanding of the diversity of proteins involved in the reception of semiochemicals in this species.

Generic insect repellent detector from the fruit fly Drosophila melanogaster

Background

Insect repellents are prophylactic tools against a number of vector-borne diseases. There is growing demand for repellents outperforming DEET in cost and safety, but with the current technologies R&D of a new product takes almost 10 years, with a prohibitive cost of $30 million dollar in part due to the demand for large-scale synthesis of thousands of test compounds of which only 1 may reach the market. R&D could be expedited and cost dramatically reduced with a molecular/physiological target to streamline putative repellents for final efficacy and toxicological tests.

Methodology

Using olfactory-based choice assay we show here that the fruit fly is repelled by not only DEET, but also IR3535 and picaridin thus suggesting they might have “generic repellent detector(s),” which may be of practical applications in new repellent screenings. We performed single unit recordings from all olfactory sensilla in the antennae and maxillary palps. Although the ab3A neuron in the wild type flies responded to picaridin, it was unresponsive to DEET and IR3535. By contrast, a neuron housed in the palp basiconic sensilla pb1 responded to DEET, IR3535, and picaridin, with apparent sensitivity higher than that of the DEET detectors in the mosquitoes Culex quinquefasciatus and Aedes aegypti. DmOr42a was transplanted from pb1 to the “empty neuron” and showed to be sensitive to the three insect repellents.

Conclusions

For the first time we have demonstrated that the fruit fly avoids not only DEET but also IR3535 and picaridin, and identified an olfactory receptor neuron (ORN), which is sensitive to these three major insect repellents. We have also identified the insect repellent-sensitive receptor, DmOr42a. This generic detector fulfils the requirements for a simplified bioassay for early screening of test insect repellents.

High-risk syndrome for neuromyelitis optica: a descriptive and comparative study

Background: Neuromyelitis optica (NMO) frequently begins with a monofocal episode of optic neuritis or myelitis. A concept named high-risk syndrome (HRS) for NMO has been proposed for patients with monofocal episodes and NMO-IgG antibodies.

Objective: To describe HRS patients and compare them with NMO patients.

Methods: We identified 30 patients with HRS: 18 with extensive myelitis (HRM) and 12 with optic neuritis (HRON), in a database pooling patients from 25 centres in France. Clinical, laboratory/magnetic resonance imaging (MRI) data and outcome were analysed and compared with a national cohort of 125 NMO patients extracted from the same database.

Results: Mean follow-up was 4.8 years. Mean age at onset was 42.8 years (range: 12.4–70) with a female:male ratio of 0.9. Asymptomatic lesions were report on visual evoked potentials in 4/8 tested HRM patients and on spinal cord MRI in 2/7 HRON patients. Three patients died, two owing to a cervical lesion. HRS and NMO patients had similar clinical/paraclinical data, except for a predominance of men in the HRS group and a later mean age at onset in the HRM subgroup.

Conclusion: The description of HRS patients is compatible with a monofocal form of NMO. Asymptomatic lesions could be included in a new set of NMO diagnostic criteria.

Long-term follow-up of neuromyelitis optica with a pediatric onset

BACKGROUND

Neuromyelitis optica (NMO) is a rare inflammatory disease. Average age at onset is 35 years. Few data exist on patients with pediatric-onset NMO (p-NMO), with disease onset before age 18 years. We report the clinical and paraclinical features and long-term outcome of patients with p-NMO and compare them with a large adult-onset NMO (a-NMO) cohort.

METHODS

We performed a retrospective, multicenter study of patients with p-NMO in pediatric and adult medical centers. We identified 125 patients with NMO (12 p-NMO; 113 a-NMO) fulfilling the 2006 criteria. Data were collected using hospital files and standardized assessment forms for NMO.

RESULTS

Patients with p-NMO were followed up during a mean 19.3 years. Median age at onset was 14.5 years (4.1-17.9) with a female:male ratio of 3:1. Three patients (25%) fulfilled Paty criteria for multiple sclerosis on first brain MRI, including one patient with acute disseminated encephalomyelitis. Median interval between onset and residual Expanded Disability Status Scale (EDSS) score 4 was 20.7 years, score 6 was 26 years, and score 7 was 28.7 years. Median interval between onset and residual visual loss ≤1/10 was 1.3 years. Compared with a-NMO, p-NMO showed a longer time to EDSS scores 4 and 6, largely explained by the severity of the first myelitis in the a-NMO group. Time to first treatment was longer in the p-NMO group (13.1 vs 3.4 years).

CONCLUSION

Patients with p-NMO can present a diffuse inflammatory process on first brain MRI and have a longer time to disability than patients with a-NMO.

Odorant receptor from the southern house mosquito narrowly tuned to the oviposition attractant skatole

Oviposition attractants are environmental cues that allow Culex gravid female mosquitoes to locate suitable sites for egg-laying and, therefore, may be exploited for environmentally friendly strategies for controlling mosquito populations. Naturally occurring skatole has been identified as an oviposition attractant for the Southern House mosquito, Culex quinquefasciatus. Previously, we identified in Cx. quinquefasciatus female antennae an olfactory receptor neuron (ORN) highly sensitive to skatole and an odorant-binding protein involved in the detection of this semiochemical. Here, we describe the characterization of an odorant receptor (OR), CquiOR10, which is narrowly tuned to skatole when expressed in the Xenopus oocyte system. Odorant-induced response profiles generated by heterologously expressed CquiOR10 suggest that this OR is expressed in the mosquito ORN sensitive to skatole. However, geranylacetone, which stimulates the antennal ORN, was not detected by CquiOR10-expressing oocytes, thus raising interesting questions about reception of oviposition attractants in mosquitoes.

An odorant receptor from the southern house mosquito Culex pipiens quinquefasciatus sensitive to oviposition attractants

Background

Insect odorant receptors (ORs) are heteromers comprised of highly variable odorant-binding subunits associated with one conserved co-receptor. They are potential molecular targets for the development of novel mosquito attractants and repellents. ORs have been identified in the malaria mosquito, Anopheles gambiae, and in the yellow fever mosquito, Aedes aegypti. However, they are still unknown in the Southern house mosquito, Culex quinquefasciatus, which transmits pathogens that cause human diseases throughout the world, including West Nile Virus in the United States.

Methodology

We have employed a combination of bioinformatics, molecular cloning and electrophysiology approaches to identify and characterize the response profile of an OR in Cx. quinquefasciatus. First, we have unveiled a large multigenic family of one-hundred-fifty-eight putative ORs in this species, including a subgroup of conserved ORs in three mosquito species. Using the Xenopus oocytes expression system, we have determined the response profile of CquiOR2, an antennae-specific OR, which shares high identity with putative orthologs in Anopheles gambiae (AgamOR2) and Aedes aegypti (AaegOR2).

Conclusion

We show that CquiOR2 is highly sensitive to indole, an oviposition attractant for Cx. quinquefasciatus. The response profile of CquiOR2 expressed in Xenopus oocytes resembles that of an olfactory receptor neuron housed in the antennal short blunt-tipped sensilla (A2) of Cx. quinquefasciatus, which are natural detectors for oviposition attractants. This first Culex OR de-orphanized is, therefore, a potential molecular target for screening oviposition attractants.

Neuromyelitis optica in France: a multicenter study of 125 patients

BACKGROUND

There have been few epidemiologic studies on neuromyelitis optica (NMO) and none used the recent 2006 diagnostic criteria. Here we describe the clinical, laboratory, MRI, and disability course of NMO in a French cohort of 125 patients.

METHODS

We performed an observational, retrospective, multicenter study. Data were collected from September 2007 through August 2008, corresponding to the endpoint of the study. We identified 125 patients fulfilling the 2006 NMO criteria. Selection was made using hospital files and a specific clinical questionnaire for NMO.

RESULTS

Mean age at onset was 34.5 years (range 4-66) with a mean disease duration of 10 +/- 7.8 years at the endpoint. The patients were mainly (87%) Caucasian, with a female:male ratio of 3:1. In 90% of cases, the association of optic neuritis, longitudinal extensive myelitis, and a Paty-negative initial brain MRI was sufficient to fulfill the supportive criteria. Eighty-eight percent of patients were treated with immunosuppressive therapies. Median delay from onset to Expanded Disability Status Scale (EDSS) score 4 was 7 years; score 6, 10 years; and score 7, 21 years. The first episode of myelitis was immediately followed by an EDSS score > or = 4 in 37.3% of cases, and a severe residual visual loss was observed in 22% of patients after the first episode of optic neuritis. Multivariate analysis did not reveal any predictors of a poor evolution other than a high number of MRI brain lesions at diagnosis, which were predictive of a residual visual acuity < or = 1/10.

CONCLUSIONS

Our demographic data provide new data on disability in patients with neuromyelitis optica, most of whom were receiving treatment.

Knockdown of a mosquito odorant-binding protein involved in the sensitive detection of oviposition attractants

Odorant-binding proteins (OBPs) were discovered almost three decades ago, but there is still considerable debate regarding their role(s) in insect olfaction, particularly due to our inability to knockdown OBPs and demonstrate their direct phenotypic effects. By using RNA interference (RNAi), we reduced transcription of a major OBP gene, CquiOBP1, in the antennae of the Southern house mosquito, Culex quinquefasciatus. Previously, we had demonstrated that the mosquito oviposition pheromone (MOP) binds to CquiOBP1, which is expressed in MOP-sensitive sensilla. Antennae of RNAi-treated mosquitoes showed significantly lower electrophysiological responses to known mosquito oviposition attractants than the antennae of water-injected, control mosquitoes. While electroantennogram (EAG) responses to MOP, skatole, and indole were reduced in the knockdowns, there was no significant difference in the EAG responses from RNAi-treated and water-injected mosquito antennae to nonanal at all doses tested. These data suggest that CquiOBP1 is involved in the reception of some oviposition attractants, and that high levels of OBPs expression are essential for the sensitivity of the insect's olfactory system.

Chemical ecology of animal and human pathogen vectors in a changing global climate

Infectious diseases affecting livestock and human health that involve vector-borne pathogens are a global problem, unrestricted by borders or boundaries, which may be exacerbated by changing global climate. Thus, the availability of effective tools for control of pathogen vectors is of the utmost importance. The aim of this article is to review, selectively, current knowledge of the chemical ecology of pathogen vectors that affect livestock and human health in the developed and developing world, based on key note lectures presented in a symposium on "The Chemical Ecology of Disease Vectors" at the 25th Annual ISCE meeting in Neuchatel, Switzerland. The focus is on the deployment of semiochemicals for monitoring and control strategies, and discusses briefly future directions that such research should proceed along, bearing in mind the environmental challenges associated with climate change that we will face during the 21st century.

Olfactory proteins mediating chemical communication in the navel orangeworm moth, Amyelois transitella

BACKGROUND

The navel orangeworm, Amyelois transitella Walker (Lepidoptera: Pyralidae), is the most serious insect pest of almonds and pistachios in California for which environmentally friendly alternative methods of control--like pheromone-based approaches--are highly desirable. Some constituents of the sex pheromone are unstable and could be replaced with parapheromones, which may be designed on the basis of molecular interaction of pheromones and pheromone-detecting olfactory proteins.

METHODOLOGY

By analyzing extracts from olfactory and non-olfactory tissues, we identified putative olfactory proteins, obtained their N-terminal amino acid sequences by Edman degradation, and used degenerate primers to clone the corresponding cDNAs by SMART RACE. Additionally, we used degenerate primers based on conserved sequences of known proteins to fish out other candidate olfactory genes. We expressed the gene encoding a newly identified pheromone-binding protein, which was analyzed by circular dichroism, fluorescence, and nuclear magnetic resonance, and used in a binding assay to assess affinity to pheromone components.

CONCLUSION

We have cloned nine cDNAs encoding olfactory proteins from the navel orangeworm, including two pheromone-binding proteins, two general odorant-binding proteins, one chemosensory protein, one glutathione S-transferase, one antennal binding protein X, one sensory neuron membrane protein, and one odorant receptor. Of these, AtraPBP1 is highly enriched in male antennae. Fluorescence, CD and NMR studies suggest a dramatic pH-dependent conformational change, with high affinity to pheromone constituents at neutral pH and no binding at low pH.

Genome analysis and expression patterns of odorant-binding proteins from the Southern House mosquito Culex pipiens quinquefasciatus

Olfactory-based behaviors in mosquitoes are mediated by odorant-binding proteins (OBPs). They form a multigenic family involved in the peripheral events in insect olfaction, specifically the transport of odorants to membrane-bound odorant receptors. OBPs contribute to the remarkable sensitivity of the insect's olfactory system and may be involved in the selective transport of odorants.We have employed a combination of bioinformatics and molecular approaches to identify and characterize members of the "classic" OBP family in the Southern House mosquito Culex pipiens quinquefasciatus ( = Cx. quinquefasciatus), a vector of pathogens causing several human diseases. By taking advantage of the recently released genome sequences, we have identified fifty-three putative Cx. quinquefasciatus OBP genes by Blast searches. As a first step towards their molecular characterization, expression patterns by RT-PCR revealed thirteen genes that were detected exclusively and abundantly in chemosensory tissues. No clear differences were observed in the transcripts levels of olfactory-specific OBPs between antennae of both sexes using semi-quantitative RT-PCR. Phylogenetic and comparative analysis revealed orthologous of Cx. quinquefasciatus OBPs in Anopheles gambiae and Aedes aegypti. The identification of fifty-three putative OBP genes in Cx. quinquefasciatus highlights the diversity of this family. Tissue-specificity study suggests the existence of different functional classes within the mosquito OBP family. Most genes were detected in chemosensory as well as non chemosensory tissues indicating that they might be encapsulins, but not necessarily olfactory proteins. On the other hand, thirteen "true" OBP genes were detected exclusively in olfactory tissues and might be involved specifically in the detection of "key" semiochemicals. Interestingly, in Cx. quinquefasciatus olfactory-specific OBPs belong exclusively to four distinct phylogenetic groups which are particularly well conserved among three mosquito species.

[Cognitive impairment]

Cognitive impairment is common in multiple sclerosis (MS), occurring at all stages of the disease, even at the earliest, and can be a major source of disability, social impairment, and impoverished quality of life. Cognitive dysfunction is mainly focused on working memory, conceptual reasoning, verbal fluency, speed of information processing, attention and executive function. Measures of information-processing speed appear to be the most robust and sensitive markers of cognitive impairment in MS patients. Cognitive testing in MS patients is complex and cognitive screening tests are time- and cost-saving test instruments. A comprehensive and sensitive cognitive test procedure should be administered to detect cognitive dysfunction, and recent studies demonstrate that single, predominantly speed-related cognitive tests may be superior to extensive and time-consuming test batteries in screening cognitive decline. Additional clinical factors, including disease course, fatigue, and affective disturbance, can impact the degree of MS-related cognitive impairment. Despite weak correlation with disease duration and physical disability status, the degree of cognitive impairment in MS has been related to the extent of topographically specific neuronal tissue damage and loss. Numerous studies have applied conventional and quantitative magnetic resonance imaging (MRI) techniques to correlate the profile and degree of cognitive impairment with various MRI-detectable abnormalities. The burden of MRI-visible lesions does not fully account for the degree of MS-related cognitive impairment. Nonconventional MRI findings suggest the extent of subtle tissue damage in normal-appearing white and grey matter to correlate best with the severity of cognitive impairment in MS patients. Structural MRI approaches have recently been extended by functional MRI studies scrutinizing the brain's ability for adaptive functional reorganization in the presence of widespread tissue damage. Cognitive impairment in MS seems to be not simply the result of tissue destruction, but also a balance between tissue destruction, tissue repair, and adaptive functional reorganization. These findings highlight the need to screen for cognitive deficits in MS patients to conduct potential cognitive rehabilitation intervention.

The onset location of multiple sclerosis predicts the location of subsequent relapses

BACKGROUND

Demyelinating events in relapsing-remitting multiple sclerosis (RRMS) can involve several locations in the central nervous system. We sought to determine if initial clinical demyelinating event (IDE) location predicts subsequent clinical relapse locations in early RRMS.

METHODS

We identified all RRMS patients from two large MS clinics who were seen within 1 year of disease onset. Logistic regression was performed with the outcome defined as the second or third exacerbation location and the predictor defined as IDE+/-second event location.

RESULTS

195 patients with at least two clinical exacerbations were identified. There was an increased odds of a patient's second relapse occurring in the spinal cord if the IDE was in the spinal cord (odds ratio (OR) = 3.79, 95% CI 2.06 to 7.00, p<0.001). There was more than a sixfold increase in the odds of a patient's second relapse occurring in the optic nerve if the IDE was in the optic nerve (OR = 6.18, 95% CI 2.90 to 13.18, p<0.001). These associations remained similar after adjusting for treatment and patient characteristics. If the IDE and second event were both in the same location (spinal cord, optic nerve or brainstem/cerebellum), the third event was likely to remain in that location.

CONCLUSION

Patients with RRMS have relatively localised clinical relapses. It remains to be determined if genetic or biological processes are responsible for this pattern.

Plasticity in MS: from Functional Imaging to Rehabilitation

One of the main characteristics of multiple sclerosis (MS) is the existence of a "clinico-radiological paradox". The discrepancies observed between the clinical and radiological findings might be partly attributable to lack of specificity of the imaging measures, but also to functional reorganization mechanisms occurring at both the brain and spinal cord levels. These neuroplastic processes might provide a means of delaying the clinical expression of some functional symptoms. Functional MRI (fMRI) methods provide a useful means of determining whether functional reorganization mechanisms of this kind are at work. It has been established, for example, that these neuroplastic mechanisms occur right from the start of the disease and may contribute to reducing the expression of the symptoms resulting from pathological tissue damage. This functional reorganization may therefore constitute an important adaptive mechanism during the early stages of the disease. One potential practical application of the findings made on these neuroplastic processes is likely to be the development of specific rehabilitation methods, which can be used to enhance these reactive mechanisms in order to maintain MS patients functional abilities, and other specifically targeted approaches will also predictably be developed.

The eIF4E-binding proteins are modifiers of cytoplasmic eIF4E relocalization during the heat shock response

Stress granules (SGs) arise as a consequence of cellular stress, contain stalled translation preinitiation complexes, and are associated with cell survival during environmental insults. SGs are dynamic entities with proteins relocating into and out of them during stress. Among the repertoire of proteins present in SGs is eukaryotic initiation factor 4E (eIF4E), a translation factor required for cap-dependent translation and that regulates a rate-limiting step for protein synthesis. Herein, we demonstrate that localization of eIF4E to SGs is dependent on the presence of a family of repressor proteins, eIF4E-binding proteins (4E-BPs). Our results demonstrate that 4E-BPs regulate the SG localization of eIF4E.

Motor evoked potentials in clinically isolated syndrome suggestive of multiple sclerosis

The aim of the present study was to determine the sensitivity and the profile of motor evoked potentials (MEP) in patients with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS). We measured the central motor conduction time (CMCT), amplitude ratio (AR), and surface ratio (SR) in tibialis anterior and first dorsal interosseous muscles in 22 patients with CIS. In 12 patients, the triple stimulation technique (TST) was also performed. AR was abnormal in 50% of patients, CMCT in 18% of patients, and TST in 25% of patients. AR had the highest sub-clinical sensitivity and the best positive predictive value. In the absence of clinical pyramidal signs, an early AR decrease seems to result from demyelination inducing excessive temporal dispersion of the MEP, while in territories with clinical pyramidal signs, it seems to result from conduction failure, which suggests that clinical pyramidal signs may be attributable to conduction failure. This study demonstrates that MEP, especially the AR, is sensitive to motor pathway dysfunction right from the early stages of MS.

Localization of plasma membrane bound NTPDases in the murine reproductive tract

Extracellular nucleotides might influence aspects of the biology of reproduction in that ATP affects smooth muscle contraction, participates in steroidogenesis and spermatogenesis, and also regulates transepithelial transport, as in oviducts. Activation of cellular nucleotide purinergic receptors is influenced by four plasma membrane-bound members of the ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) family, namely NTPDase1, NTPDase2, NTPDase3, and NTPDase8 that differ in their ecto-enzymatic properties. The purpose of this study was to characterize the expression profile of the membrane-bound NTPDases in the murine female and male reproductive tracts by immunological techniques (immunolabelling, Western blotting) and by enzymatic assays, in situ and on tissue homogenates. Other than the expected expression on vascular endothelial and smooth muscle cells, NTPDase1 was also detected in Sertoli cells and interstitial macrophages in testes, in ovarian granulosa cells, and in apical cells from epididymal epithelium. NTPDase2 was largely expressed by cells in the connective tissue; NTPDase3 in secretory epithelia, and finally, NTPDase8 was not detected in any of the tissues studied here. In addition, NTPDase6 was putatively detected in Golgi-phase acrosome vesicles of round spermatids. This descriptive study suggests close regulation of extracellular nucleotide levels in the genital tract by NTPDases that may impact specific biological functions.