Biology subjects

Vosshall, L. B.

Publications and source records attributed to Vosshall, L. B..

8 recordsLinked to original sources

bioRxiv2018

The ion channel ppk301 controls freshwater egg-laying in the mosquito Aedes aegypti

Aedes aegypti mosquitoes are deadly vectors of arboviral pathogens including Zika, dengue, and yellow fever, and breed in containers of freshwater associated with human habitation1,2. Female Ae. aegypti lay eggs near freshwater because larval and pupal stages are aquatic3. They use volatile cues to locate water at a distance4, while at close-range they contact water to evaluate its suitability for egg-laying4-7. High salinity is lethal to mosquito offspring and therefore correctly laying eggs in freshwater is a crucial parenting decision made by female mosquitoes. Here we show that the DEG/ENaC channel8-10 ppk301 is required for mosquitoes to exploit freshwater egg-laying substrates. When ppk301 mutant females contact water, they do not lay eggs as readily as wild-type animals and are more likely to make aberrant decisions between freshwater and saltwater at concentrations that impair offspring survival. We used a CRISPR-Cas9-based genetic knock-in strategy combined with the Q-binary transactivator system11 to build genetic tools for labelling and imaging neurons in the mosquito. We found that ppk301 is expressed in sensory neurons in legs and proboscis, appendages that directly contact water, and that ppk301-expressing neurons project to central taste centres. Using in vivo calcium imaging with the genetically-encoded calcium sensor GCaMP6s12, we found that ppk301-expressing cells respond to water but, unexpectedly, also to salt. This suggests that ppk301 is instructive for egg-laying at low salt concentrations but that a ppk301-independent pathway is responsible for inhibiting egg-laying at high salt concentrations. Water is a key resource for insect survival and understanding how mosquitoes interact with water to control different behaviours is an opportunity to study the evolution of chemosensory systems. The new genetic tools described here will enable direct study of not only egg-laying, but also other behaviours in mosquitoes that influence disease transmission and enable comparative studies of insect biology more broadly.

neuroscience↗

bioRxiv2018

Novel small molecule agonists of an Aedes aegypti neuropeptide Y receptor block mosquito biting behavior

Female Aedes aegypti mosquitoes bite humans to obtain a blood-meal to develop their eggs. Remarkably, strong attraction to humans is suppressed for several days after the blood-meal by an unknown mechanism. We investigated a role for neuropeptide Y (NPY)-related signaling in this long-term behavioral suppression, and discovered that drugs targeting human NPY receptors modulate mosquito host-seeking behavior. In a screen of all 49 predicted Ae. aegypti peptide receptors, we identified NPY-like receptor 7 (NPYLR7) as the sole target of these human drugs. To obtain small molecule agonists selective for NPYLR7, we carried out a high-throughput cell-based assay of 265,211 compounds, and isolated 6 highly selective NPYLR7 agonists that inhibit mosquito attraction to humans. NPYLR7 CRISPR-Cas9 null mutants are defective in behavioral suppression, and resistant to these drugs. Finally, we show that these drugs are capable of inhibiting biting and blood-feeding on a live host, suggesting a novel approach to control infectious disease transmission by controlling mosquito behavior.

neuroscience↗

bioRxiv2018

DEET feet: Aedes aegypti mosquitoes use their tarsi to sense DEET on contact

DEET (N, N-diethyl-meta-toluamide) is the most effective and broadly used insect repellent, but its mechanism of action is both complex and controversial [1]. Previous work demonstrated that DEET acts both on insect smell [2-6] and taste [7-11] systems. Its olfactory mode of action requires the odorant co-receptor orco [2, 3, 6], while its gustatory repellency is mediated by activation of bitter taste receptors and neurons in the proboscis upon ingestion [8]. Together, these data have led to the assumption that DEET acts only on olfactory and gustatory pathways. We previously observed that orco mutant female Aedes aegypti mosquitoes are strongly attracted to humans even in the presence of DEET, but are rapidly repelled after contacting DEET-treated skin [6]. To understand the basis of this contact chemorepellency, we carried out a series of behavioral experiments and discovered that DEET acts in three distinct ways: through smell, taste, and contact. DEET and bitter tastants are feeding deterrents when ingested, but only DEET is capable of mediating contact repellency on human skin. We show that the repellent touch of DEET is mediated by the tarsal segments of the legs, and not gustatory neurons in the proboscis as previously believed. This work establishes mosquito leg appendages as the actual sensors of DEET, and highlights the existence of an unknown sensory pathway that is independent of bitter taste. These results will inform the search for novel contact-based insect repellents.\n\nHighlightsO_LIDEET and bitters are both repellent when ingested by Aedes aegypti female mosquitoes\nC_LIO_LIOnly DEET is additionally repellent upon contact\nC_LIO_LIRepellency of DEET on skin is mediated solely by the legs\nC_LIO_LIAny of the three pairs of legs can sense DEET and prevent mosquitoes from biting\nC_LI

neuroscience↗

bioRxiv2017

Genetic variation across the human olfactory receptor repertoire alters odor perception

The human olfactory receptor repertoire is characterized by an abundance of genetic variation that affects receptor response, but the perceptual effects of this variation are unclear. To address this issue, we sequenced the OR repertoire in 332 individuals and examined the relationship between genetic variation and 276 olfactory phenotypes, including the perceived intensity and pleasantness of 68 odorants at two concentrations, detection thresholds of three odorants, and general olfactory acuity. Genetic variation in a single OR frequently associated with odorant perception, and we validated 10 cases in which in vitro OR function correlated with in vivo odorant perception using a functional assay. This more than doubles the published examples of this phenomenon. For eight of these 10 cases, reduced receptor function associated with reduced intensity perception. In addition, we used participant genotypes to quantify genetic ancestry and found that, in combination with single OR genotype, age and gender, we can explain between 10 and 20% of the perceptual variation in 15 olfactory phenotypes, highlighting the importance of single OR genotype, ancestry, and demographic factors in variation of olfactory perception.

genetics↗

bioRxiv2017

A natural variant and an engineered mutation in a GPCR promote DEET resistance in C. elegans

DEET (N,N-diethyl-meta-toluamide) is a synthetic chemical, identified by the United States Department of Agriculture in 1946 in a screen for repellents to protect soldiers from mosquito-borne diseases1,2. Since its discovery, DEET has become the worlds most widely used arthropod repellent3, and is effective against invertebrates separated by millions of years of evolution, including biting flies4, honeybees5, ticks6, and land leeches4,7. In insects, DEET acts on the olfactory system5,8-14 and requires the olfactory receptor co-receptor orco9,11-13, but its specific mechanism of action remains controversial. Here we show that the nematode Caenorhabditis elegans is sensitive to DEET, and use this genetically-tractable animal to study its mechanism of action. We found that DEET is not a volatile repellent, but interferes selectively with chemotaxis to a variety of attractant and repellent molecules. DEET increases pause lengths to disrupt chemotaxis to some odours but not others. In a forward genetic screen for DEET-resistant animals, we identified a single G protein-coupled receptor, str-217, which is expressed in a single pair of DEET-responsive chemosensory neurons, ADL. Misexpression of str-217 in another chemosensory neuron conferred strong responses to DEET. Both engineered str-217 mutants and a wild isolate of C. elegans carrying a deletion in str-217 are DEET-resistant. We found that DEET can interfere with behaviour by inducing an increase in average pause length during locomotion, and show that this increase in pausing requires both str-217 and ADL neurons. Finally, we demonstrated that ADL neurons are activated by DEET and that optogenetic activation of ADL increased average pause length. This is consistent with the \"confusant\" hypothesis, in which DEET is not a simple repellent but modulates multiple olfactory pathways to scramble behavioural responses12,13. Our results suggest a consistent motif for the effectiveness of DEET across widely divergent taxa: an effect on multiple chemosensory neurons to disrupt the pairing between odorant stimulus and behavioural response.

neuroscience↗

bioRxiv2017

SMELL-S and SMELL-R: olfactory tests not influenced by odor-specific insensitivity or prior olfactory experience

Smell dysfunction is a common and underdiagnosed medical condition that can have serious consequences. It is also an early biomarker of Alzheimers disease that precedes detectable memory loss. Clinical tests that evaluate the sense of smell face two major challenges. First, human sensitivity to individual odorants varies significantly, leading to potential misdiagnosis of people with an otherwise normal sense of smell but insensitivity to the test odorant. Second, prior familiarity with odor stimuli can bias smell test performance. We have developed new non- semantic tests for olfactory sensitivity (SMELL-S) and olfactory resolution (SMELL-R) that overcome these challenges by using mixtures of odorants that have unfamiliar smells. The tests can be self-administered with minimal training and showed high test-retest reliability. Because SMELL-S uses odor mixtures rather than a single molecule, odor-specific insensitivity is averaged out. Indeed, SMELL-S accurately distinguished people with normal and dysfunctional smell. SMELL-R is a discrimination test in which the difference between two stimulus mixtures can be altered stepwise. This is an advance over current discrimination tests, which ask subjects to discriminate monomolecular odorants whose difference cannot be objectively calculated. SMELL-R showed significantly less bias in scores between North American and Taiwanese subjects than conventional semantically-based smell tests that need to be adapted and translated to different populations. We predict that SMELL-S and SMELL-R will be broadly effective in diagnosing smell dysfunction, including that associated with the earliest signs of memory loss in Alzheimers disease.\n\nSignificance statementCurrently available smell testing methods can misdiagnose subjects with lack of prior experience or insensitivity to the odorants used in the test. This introduces a source of bias into clinical tests aimed at detecting patients with olfactory dysfunction. We have developed smell tests that use mixtures of 30 molecules that average out the variability in sensitivity to individual molecules. Because these mixtures have unfamiliar odors, and the tests are non-semantic, their use eliminates differences in test performance due to the familiarity with the smells or the words used to describe them. The SMELL-S and SMELL-R tests facilitate smell testing of diverse populations, without the need to adapt the test stimuli.

neuroscience↗

bioRxiv2017

A Neuropeptide Signaling System That Rapidly Enforces Paternity In The Aedes aegypti Mosquito

Female Dengue and Zika vector mosquitoes (Aedes aegypti) generally mate once, with sperm from this male fertilizing all eggs produced in her lifetime. Here we implicate HP-I, an Aedes- and male-specific neuropeptide transferred to females, and its cognate receptor in the female, NPYLR1, in rapid enforcement of paternity. HP-I mutant males were ineffective in enforcing paternity when a second male was given access to the female within 1 hour. NPYLR1 mutant females produced mixed paternity offspring at high frequency. Synthetic HP-I injected into wild-type virgins reduced successful matings, but had no effect on NPYLR1 mutant females. Asian tiger mosquito (Ae. albopictus) HP-I potently activated Ae. aegypti NPYLR1. Invasive Ae. albopictus males are known to copulate with and sterilize Ae. aegypti females, and cross-species transfer of HP-I may contribute to this phenomenon. This neuropeptide system promotes rapid paternity enforcement within Ae. aegypti, but may promote local extinction in areas where they compete with Ae. albopictus.\n\nOne Sentence SummaryAedes-specific peptide rapidly enforces paternity\n\nTextAe. aegypti females typically mate only once with one male in their lifetime, a behavior known as \"monandry\" (1). This single mating event provisions the female with sufficient sperm to fertilize the >500 eggs she will produce during her [~]4-6 week lifespan in the laboratory (2). Successful mating is capable of inducing lifetime refractoriness to subsequent insemination by other males, enforcing the paternity of the first male (3-5). In other species, males use diverse strategies to assure the paternity of their offspring, for instance physical barriers such as mating plugs found in mice (6) and Anopheline mosquitoes (7), and anti-aphrodisiac pheromones used by Drosophila melanogaster males to tag female flies as non-virgin (8). Another widely used strategy in insects is the transfer of biologically active male seminal proteins, produced by the male accessory gland and secreted into the ejaculatory duct along with sperm during insemination, to affect the sexual receptivity of the female (3, 9-13). Perhaps the best-characterized male seminal fluid protein in insects is the Drosophila fly sex peptide (11), which acts on the sex peptide receptor in the female to suppress receptivity and trigger egg production (12). Drosophila sex peptide receptor mutant females will readily remate with multiple males, and wild-type females that mate with sex peptide mutant males remain sexually receptive.

neuroscience↗

bioRxiv2016

Reverse-engineering human olfactory perception from chemical features of odor molecules

Despite 25 years of progress in understanding the molecular mechanisms of olfaction, it is still not possible to predict whether a given molecule will have a perceived odor, or what olfactory percept it will produce. To address this stimulus-percept problem for olfaction, we organized the crowd-sourced DREAM Olfaction Prediction Challenge. Working from a large olfactory psychophysical dataset, teams developed machine learning algorithms to predict sensory attributes of molecules based on their chemoinformatic features. The resulting models predicted odor intensity and pleasantness with high accuracy, and also successfully predicted eight semantic descriptors (\"garlic\", \"fish\", \"sweet\", \"fruit\", \"burnt\", \"spices\", \"flower\", \"sour\"). Regularized linear models performed nearly as well as random-forest-based approaches, with a predictive accuracy that closely approaches a key theoretical limit. The models presented here make it possible to predict the perceptual qualities of virtually any molecule with an impressive degree of accuracy to reverse-engineer the smell of a molecule.\n\nOne Sentence SummaryResults of a crowdsourcing competition show that it is possible to accurately predict and reverse-engineer the smell of a molecule.

neuroscience↗