Biogenic amines in malaria mosquitoes: from hearing to swarming behaviour

Lead Research Organisation: University College London
Department Name: Ear Institute

Abstract

Mosquitoes are more sensitive to sound than any other arthropod, by means of their fascinating tiny antennal ears, the Johnston 's organ (JO). In an organ smaller that a pin's head, male mosquitoes harbour around 15,000 auditory neurons roughly equalling the number of hair in human cochlea. Mosquitoes use their sophisticated JO's to recognize the flight tones of mating partners. Every day around sunset, male mosquitoes aggregate in areal swarms that attract females. Within swarms, male and female acoustically detect each other by their wing beats. Due to the necessity for mosquito mating, pre-mating acoustic interactions and swarming behaviour are prime targets for mosquito control tools. Despite this, the neurobiology of mosquito swarming behaviour, and the physiological mechanisms that induce it, are almost entirely unknown.
We have recently shown how the mosquito JO function is modulated by an auditory efferent system. This is remarkable as auditory efferent control was believed to exist only in vertebrates. We show that the biogenic amines octopamine and serotonin are released in the mosquito JO and modulate sound-induced mechanical and electrical responses, likely contributing to JO's sophistication as sound detector. Interestingly, biogenic amines induce swarming and social behaviour in other insects. Taken together and given the intimate relationship between hearing and swarming behaviour in mosquitoes I hypothesized that they also induce mosquito aggregation in swarms and tune the mosquito auditory sensitivity to the flight tone of mating partners to maximize mating success. I argue that interfering with serotonin and octopamine signalling pathways could be a novel mosquito control target to impair hearing and swarming and consequently hinder mosquito mating.
My preliminary data support this hypothesis: i) the levels of octopamine and serotonin receptors in the mosquito JO change during the time when mosquitoes are swarming, ii) the auditory sensitivity of male mosquito JO increases during swarming, and this effect is mimicked after injecting octopamine. In this project, I will use a multidisciplinary approach bridging the fields of molecular biology, physiology and behaviour to study the physiological and behavioural changes induced by octopamine and serotonin in malaria-transmitting Anopheles gambiae mosquitoes with the declared goal of devising novel vector control tools.
To investigate this, I will first analyse the connection between the octopaminergic and serotonergic signalling in the mosquito JO and the circadian clock. I will study if octopamine and serotonin levels change during swarming and how these changes reflect shifts in auditory sensitivity. I will then disrupt these pathways by generating serotonin and octopamine receptor mutants and study the auditory and swarming behaviour phenotypes. Finally, I aim to translate these findings into innovative mosquito control tools by using the acquired knowledge to disrupt swarming behaviour in semi-field settings in a malaria endemic country.

Planned Impact

The rapid emergence of insecticide resistance among mosquito populations, alongside behavioural adaptations enabling evasion of control tools, makes a compelling case for developing novel control interventions. Due to their necessity for mating, hearing and swarming are promising targets. However, they have been underexploited due to extensive gaps in knowledge of the mosquito auditory behaviour and the molecular mechanisms involved. This project will produce data in two main areas with potential public health impact: i) physiological and behavioural data of mosquito auditory sensitivity that can be translated into the development of acoustic traps to lure and kill mosquitoes and inform the development of acoustic sensors as a novel high-throughput method for mosquito surveillance; ii) potential of interfering BA signalling to impair mosquito mating. OA/5-HT signal through G-protein coupled receptors that are considered promising targets for the development of next generation insecticides. Interestingly, OA (invertebrate counterpart of noradrenaline) is preferably synthetized in invertebrates and is only present as traces in mammals, so their receptors are promising potential targets for highly specific insecticides. Building on this project, I will develop a research career focused on providing rigorous physiological and behavioural data to incorporate acoustic traps and swarming impairment approaches into the spectrum of interventions to fight mosquito vector diseases.
The findings will be relevant for a broad audience. Medical entomologist and other public health stakeholders working in malaria control will be interested in the results, as evidence-based practices for malaria control con be derived from them. To reach them I will attend applied research conferences where different actors working on malaria control come together.
The project will also shed light on the molecular mechanisms underlying a fascinating sensory organ. I will characterize the first auditory efferent system describe in insects. This is highly relevant for other academic audiences, such as insect physiologists and vector biologists. Findings will reach these scientists by participating in conferences and publishing the research in high impact and open access journals.
The general public will also benefit from the results, as mosquito-borne diseases are a cause of mortality and morbidity worldwide, and mosquito species with the potential to transmit disease are spreading in Europe, due to the increase in international travel and the climate change. Different outreach activities will be organized to ensure that the research relevance has an impact on the wider public. In particular, public engagement activities will be performed in schools, both in UK and Tanzania, to ensure that future generations understand the importance of mosquito-borne disease and how to better protect themselves against mosquito bites.

Publications

10 25 50
 
Description 752472 NEURO-SWARM - Efferent modulation of auditory sensitivity in mosquitoes: From auditory transduction to swarming behaviour
Amount € 183,455 (EUR)
Funding ID 752472 NEURO-SWARM 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2017 
End 03/2019
 
Description Biogenic amines in malaria mosquitoes: from hearing to swarming behaviour
Amount £55,327 (GBP)
Funding ID ISSF3/ H17RCO/NG21 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2020 
End 12/2021
 
Description Characterising the mating songs of malaria mosquitoes in Tanzania.
Amount £2,000 (GBP)
Organisation University College London 
Department UCL Global Engagement Office
Sector Academic/University
Country United Kingdom
Start 08/2019 
End 09/2019
 
Description Disrupting octopamine signalling for mosquito control
Amount £87,189 (GBP)
Organisation University College London 
Department UCL Global Engagement Office
Sector Academic/University
Country United Kingdom
Start 01/2020 
End 07/2020
 
Title Knock-outs of three serotonin receptors in malaria mosquitoes 
Description We have used the genome-editing technique CRISPR-Cas9 to generate three Anopheles gambiae mosquito lines, each mutant for a different serotonin receptor. 
Type Of Material Biological samples 
Year Produced 2022 
Provided To Others? No  
Impact Serotonin is an important neurotransmitter that regulates different insect behaviors. These mutant lines will enable the research community to investigate the role of serotonin receptors in different biological processes, and to understand whether serotonin pathways can be targeted as part of novel mosquito control strategies. The lines will be available to the research community upon publication the results. 
 
Title New antibody against three serotonin receptors in the malaria mosquito 
Description Antibodies against three different serotonin receptors of the malaria mosquito Anopheles gambiae where generated by immunizing guinea pigs and rabbits using short peptides uniques to these receptors. We are still testing the specificity these antibodies and we will make them available once the results are published 
Type Of Material Antibody 
Year Produced 2022 
Provided To Others? No  
Impact These antibodies will enable to study the cellular and suocelular localization of serotonin receptors in the malaria mosquito. Serotonin is a biogenic amine neurotransmitter that is involved in controlling essential insect behaviors. Our antibody will contribute to understand the biological function that serotonin plays in malaria mosquitoes. 
 
Description Analysis of the effects of altering octopamine receptors in Plasmodium transmission in Anopheles gambiae 
Organisation TropIQ Health Sciences
Country Netherlands 
Sector Private 
PI Contribution This partnership aims at studying whether knocking-out octopamine receptors in the malaria mosquito Anopheles gambiae would lead to a reduced transmission of Plasmodium parasites by the mosquitoes. We have provided TropIQ with two different mosquito lines, each mutant for a different octopamine receptor.
Collaborator Contribution TropIQ will perform Standard Membrane Feeding Assays (SMFA) with GFP expressing Plasmodium infected blood and the infection status will be determined by luminescence assays.
Impact The experiments are still ongoing
Start Year 2021
 
Description Biogenic amines as novel targets to fight mosquito-borne diseases 
Organisation Ifakara Health Institute
Country Tanzania, United Republic of 
Sector Charity/Non Profit 
PI Contribution Knowledge on the basic biology of biogenic amines and their role in mosquito audition and swarming behaviour. Equipment to analyze this behaviour in the field.
Collaborator Contribution Medical entomology knowledge to translate our findings into mosquito control strategies. Semi-field facilities and mosquito lines to analyze mosquito swarming behaviour.
Impact ANTI-Vec Net annual meeting, June 20-21, London, United Kingdom: The acoustic landscape of disease transmitting vectors. Andres M, Su M, Somers J, Georgiades M, Ntabaliba W, Spaccapelo, R, Moore S, Albert J. Oral presentation. GCRF: UCL Internal Small Grant, 01/01-30/06/2020, Awardee: Marta Andres de Miguel, Amount awarded: £87,189.48
Start Year 2018
 
Description Drug discovery: developing a novel insecticide with antagonistic activity on malaria mosquito octopamine receptors 
Organisation University College London
Department School of Pharmacy
Country United Kingdom 
Sector Academic/University 
PI Contribution In our team, we have identified an octopamine receptor that might be a potential target for the development of novel insecticides due t the effects of blocking its activity on mosquito mating and egg development. In collaboration with Matthew Todd from UCL School of Pharmacy, we are looking for funding to develop new molecules with insecticide potential to block the activity of these receptors. We will work in the development of a cell line to express the receptor and study the effect of potential blockers at cellular and physiological level
Collaborator Contribution Matthew Todd's team will run a virtual screening to identify suitable molecules to block these receptors, and will further optimize select molecules to increase their insecticide potential.
Impact We submitted a WT Innovator Award that was not awarded but we preparing other applications to fund this research
Start Year 2021
 
Description Generation of biogenic amine receptor mutants 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Genetic constructs to generate mosquito mutant lines
Collaborator Contribution Generation of mutant mosquito lines
Impact The analysis of the mutant auditory phenotypes will be included in a publication that is almost ready for submission
Start Year 2018
 
Description Mosquito swarming behaviour analysis in the laboratory 
Organisation University of Perugia
Country Italy 
Sector Academic/University 
PI Contribution Mosquito mutant lines and equipment to analyze the mosquito swarming behaviour of mosquitoes in laboratory conditions.
Collaborator Contribution Knowledge on how to induce mosquito swarming behaviour and large cage facilities to study this behaviour. 3D recording system to analyse the trajectories of mosquitoes flying with the swarm
Impact ANTI-Vec Net annual meeting, June 20-21, London, United Kingdom: The acoustic landscape of disease transmitting vectors. Andres M, Su M, Somers J, Georgiades M, Ntabaliba W, Spaccapelo, R, Moore S, Albert J. Oral presentation.
Start Year 2017
 
Description Swarming behaviour analysis 
Organisation Polo d'Innovazione di Genomica, Genetica e Biologia
Country Italy 
Sector Academic/University 
PI Contribution We provided polo GBB with the octopamine receptor mutants to be analysed
Collaborator Contribution They performed the analysis of the mating behaviour of the octopamine receptor mutants. They provided the facilities, the analytical pipeline and the staff to perform the analysis
Impact The data has been used as preliminary data for further experiments in the lab
Start Year 2019
 
Description Crick Institute - Neuroscience Interest Group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Interest group based at the Crick Institute. We participate as associate members. The group meets every two weeks to discuss different neuroscience topics based on the research performed by the participating groups.
Year(s) Of Engagement Activity 2020,2021
 
Description Online seminar (World Wide Neuro) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact 15 people attended the online presentation. A scientific discussion followed and open new ways for collaborations with research groups at the Crick Institute
Year(s) Of Engagement Activity 2020