FLiACT has currently no open position
1. Genetic and evolutionary basis of sensory diversity: Hassan Lab, Vlaams Institute for Biotechnology, Leuven, BE
2. Molecular basis of sensory memories. Louis lab, Center for Genomic Regulation, ES
3. The fly as biomedical model system for human diseases: Brainwave-Discovery Ltd, UK
4. Neural control of behavioural changes in larvae: Sprecher lab, University of Fribourg, CH
5. Bilateral nature of sensory systems: Louis lab, Center for Genomic Regulation, ES
6. Multimodal sensory integration in courtship song: Dickson Lab, Institute of Molecular Pathology, AT
7. Neural representation of attractive olfactory inputs: Hansson Lab (Silke Sachse), Max Plank Institute, Jena, DE
8. Neuronal basis of the evolution of sensitivity to specific odours.: Gompel & Prud’homme lab, Institut de Biologie du Développement de Marseille-Luminy, FR
9. Effects of internal states on sensory input processing: Ribeiro lab, Champalimaud Centre for the Unknown, PT
10. Mapping of circuit-function relationships in adult flies: Kadow lab, Max Plank Institute, Martinsreid, DE
11. New assays to study sensory behaviours: Peira, BE
12. Novel methods for functional imaging: Digital Cell Imaging Laboratories, BE
All 12 fellows will work in close collaboration. They will receive training and execute part of their research in different FLiACT laboratories. This will be done through short visits (1-6 weeks) or longer-term secondments (2-6 months). They will also participate in a series of hands-on workshops and meetings organised during the course of their project.
Title: Genetic and evolutionary basis of sensory diversity.
Goal: Elucidating the role of Atonal in the developmental programme of sensory organs
Methodology: The formation of most sensory organs in Drosophila is governed by the activity of a single transcription factor called Atonal (Ato), suggesting a shared evolutionary origin. This observation, however, raises the question of how a single transcription factor can act differentially to specify a diversity of sensory modalities. Hassan's group has identified 27 Ato target genes and characterised their expression patterns in various sensory anlagen. To determine the role of the Ato target genes in the development and function of visual and olfactory organs, the fellow will use transgenic RNAi approaches to knockdown each of the target genes in the respective sensory organs. To address whether all sensory modalities have a common evolutionary origin, Hassan's group has tagged the ato locus with a cassette that allows highly efficient replacement of the ato coding sequence with any sequence of interest. The fellow will replace the ato coding sequence by that of ato orthologues from other insects (Drosophila species, honey bee, mosquito) as well as more divergent organisms such as annelids and sponges. She/he will then ask whether these sensory modalities resemble that of D. melanogaster or the species from which the Ato sequence originates. During year 3, the FlyWorld will be used to test potential phenotypic defects pertaining to multisensory integration.
Title: Neural computation guiding larval chemotaxis.
Goal: Clarifying the molecular and cellular mechanisms underlying the sensorimotor integration of olfactory signals
Methodology: Larval chemotaxis consists of an alternation between relatively straight runs and directed turns. In previous work, M. Louis has shown that turns are preferentially oriented towards the odor source (assuming that the odor is attractive). A turn is preceded by a series of head sweeps during which the larva monitors the stimulus intensity at different points in space. We speculate that this form of active sampling requires a short-term spatial memory - a "working memory" - where stimulus intensities associated with different positions are stored for central comparison. Combining a virtual-reality paradigm based on optogenetics with electrophysiology, the fellow will characterize the sensorimotor algorithm controlling larval chemotaxis. She/he will use a novel high-resolution tracker to probe the neural mechanisms controlling the integration of dynamical olfactory signals and its conversion into orientation decisions. These experiments will be run in collaboration with V. Jayaraman (Janelia Farm). In addition, she/he will examine whether a short-term spatial memory participates in this process. She/he will seek to clarify the molecular basis of such a memory. Particular attention will be dedicated to the gene ignorant (ign) that encodes a ribosomal S6KII-kinase. In the past, R. Stauss (University of Mainz) has shown that ign mutants are defective in operant conditioning in adult flies. During a secondment with R. Stauss, the fellow will test ign mutants for deficit in the orientation decision during chemotaxis and other forms of orientation behaviour. The analysis will be extended to additional genes involved in short-term memorization.
Title: The fly as biomedical model system for human diseases.
Objectives: Characterising the effects of ectopic expression of humanised gene products involved in memory formation and sensory control.
Methodology: Exploiting the power of Drosophila genetics, Armstrong's group has generated humanised fly strains of interest as model for nervous system disorders. The fellow will be in charge of testing these strains in various behavioural paradigms available from the network’s partners. During regular visits with Ribeiro's group (Champalimaud) and Strauss's group (UM), the fellow will test the human homologues of factors that are potentially taking part in the functioning of working memories and metabolic states evaluation. She/he will pay particular attention to ignorant, a kinase participating in the RAS-ERK (rsk) signalling pathway. In humans and mice, mutations in the rsk2 gene lead to severe memory defects. Using an adapted version of the detour paradigm developed by the fellow in charge of project 2, drugs will be selected and tested to compensate the behavioural deficiencies induced by loss-of-function of these genes and gain-of-function upon expression of humanised factors.
Title: Neural control of behavioural changes in larvae.
Goal: Identifying the neuronal substrates enabling developmentally controlled behavioural adaptation.
Methodology: Prior to pupation, larvae of D. melanogaster undergo stereotypical changes from foraging to wandering non-feeding behaviour. The fellow will identify the optimal conditions to study this behavioural transition. She/he will run a screen to identify which subtypes of neurons are involved in the behavioural switch. Recent findings show that the NP394-Gal4 line marks neurons required for maintaining larva photophobia. The fellow will anatomically address the relationship of new identified neurons in the screen to the NP394-neurons. For odours eliciting different behaviours at the foraging and wandering stages, functional imaging will be applied to second-order neurons and higher brain centres to delineate deep sites of neuronal integration. While based at UNIFR, significant support will be provided by Nicasy (Peira) and Weyn (Digital Cell) in the monitoring of behavioural changes by using bioluminescence.
Title: Bilateral nature of sensory systems.
Goal: Investigating the mechanisms and potential advantages of bilateral sensory processing.
Methodology: Most sensory systems are distributed bilaterally. Although not necessary, bilateral sensory function has been shown to provide a significant advantage for the integration of spatial cues. This project aims to understand where and how sensory information carried by bilateral sensors is merged in the larval brain. First, the fellow will test whether bilateral inputs are relevant to the function of the visual system. She/he will laser ablate the optic nerve on one side, and characterise the phototactic performances of these ‘one-eyed’ larvae. In collaboration with Sprecher (UNIFR) and Simpson (Janelia), she/he will search to identify neural circuits bridging the left and right hemispheres of the brain. This will be achieved by performing a loss-of-function screening with different collections of GAL4 driver lines. The behavioural defects resulting from this screen will be studied in odour and light gradients - Louis (CRG), Sprecher (UNIFR), and ultimately in the FlyWorld -Nicasy (Peira).
Title: Multimodal sensory integration in courtship song.
Goal: Defining the neural circuits and mechanisms that integrate chemosensory and visual information during courtship.
Methodology: A central component of the Drosophila male courtship ritual is the pulse song produced by vibrating one wing. The song is triggered in response to chemosensory signals provided by the female. Visual input is not essential for song production per se, but it guides the choice of wing. Courtship song provides an ideal paradigm for studying the neural mechanisms of multisensory integration. Activation of either of two classes of neuron in the brain – P1 and pIP10 - is both necessary and sufficient to trigger singing. pIP10 is descending and innervates the wing neuropil in the thoracic ganglia. P1 appears to provide input to pIP10 and is activated in response to chemosensory stimuli. When song is elicited by artificial activation of P1 or pIP10, the choice of wing appears arbitrary. This suggests that visual information is processed through a parallel pathway and integrated in the thoracic circuits. The fellow will conduct behavioural and anatomical screens to search for neural circuits that integrate the chemosensory and visual inputs that guide wing choice. She/he will establish new behavioural assays in which defined chemical or visual stimuli are applied in isolation or in combination during secondments with Strauss (UM) (vision), and Hansson (MPI-CE) (olfaction).
Title: Neural representation of olfactory inputs.
Goal: Unveiling the representation of odour attractiveness and repulsiveness in adult flies and larvae.
Methodology: Relying on material generated by a large screen for odour preferences, which identified 30 highly attractive stimuli and 5 highly repulsive stimuli, the fellow will first attempt to identify a representation principle for attractiveness/repulsiveness in the adult antennal lobe (AL). ESR7 will analyse AL activity at the level of the OSNs, LNs, and PNs by using calcium imaging. In a second phase, she/he will test whether we can predict the attractiveness of binary blends based on their individual components. This will be done with behavioural tests and with functional imaging. The fellow will attempt to identify a neuronal representation of odour preferences by analysing the coding patterns for attractive and repulsive odours in the adult AL. The coding of blends identified for the adult AL will be examined and compared in the much simpler larval olfactory system.
Title: Neuronal basis of the evolution of sensitivity to specific odours.
Goal: Identifying genetic and neuronal differences underlying variations in olfactory behaviours.
Methodology: Different species respond differently to similar sensory stimuli. Variations in the sensory response could be encoded in the sensory neurons and in the sensory receptors expressed in these neurons. In a screen for variations in olfactory receptor (OR) expression between Drosophila species, some species were found to depart from the rest of the survey for expression of given ORs. Preliminary data indicate that these changes in expression are associated with altered sensitivity to the corresponding odour. The project aims at characterizing and quantifying these differences in the neural response and behaviour, and identifying their cellular bases. To this end, the fellow will first make use of classical genetics in D. melanogaster to demonstrate the link between a given OR and a specific odorant compound. Then, to tackle the evolution of olfaction between species with different levels in OR expression, s/he will make reporter constructs with the regulatory regions of such ORs, then test them in different species. This is meant to reveal the molecular origin of the differences in gene expression, and look for possible changes in neuronal anatomy between species. Once the genetics and neuroanatomy of the system are clarified, the next step will be to characterize the functional changes between species. To test for causality between changes in OR expression and changed sensitivity to an odour, s/he will make use of transgenesis in different species, testing OR alleles of one species into the other, and assessing the consequences on neural activity and behavior. S/he will also take advantage of the possibility to make hybrids between some species with different levels of expression in specific ORs. Altogether, the results should identify the molecular and functional changes responsible for the evolution of sensitivity to particular odours.
Title: Effects of internal states on sensory input processing.
Goal: Identify neuronal and molecular mechanisms for the modulation of sensory perception by internal states.
Methodology: Internal states, for instance metabolic state or mating status, can affect sensory perception. Using olfactory behavioural assays, the fellow will characterise the effect of starvation and mating on olfaction. She/he will identify molecular and cellular mechanisms by which these states are conveyed to the central nervous system. Particular attention will be dedicated to the pathways downstream from two receptors: the neuropeptide F receptor (NPFR) which mediates satiation in flies, and the Sex peptide receptor (SPR), which induces drastic changes in female behaviour upon mating. She/he will test the involvement of candidate genes and candidate neurons previously characterised in mediating changes in sensory processing upon metabolic changes. Using calcium sensors, the fellow will test how changing the metabolic and mating states affect the identified neurons. She/he will collaborate with Armstrong (Brainwave) to examine the effect of ectopically expressing the human orthologues of NPY receptors in the nervous system of Drosophila. At the end of year 2, the fellow will examine internal state effects in semi-realistic environments produced by the FlyWorld (Peira).
Title: Mapping of circuit-function relationships in adult flies.
Goal: Identifying neuronal circuits involved in representative behaviours.
Methodology: The goal of this project is to discover new circuit-function relationships in adult D. melanogaster. The screen will rely on ~3000 P[GAL4] lines from the Kyoto Centre that target distinct neuronal subpopulations and on the effector lines UAS-TNT (tetanus toxin), and/or to UAS-Shi[ts] (temperature sensitive allele of shibire) to disable the GAL4-expressing neurons. The screen of the Kyoto GAL4 collection and other collection of reagents hosted by Dickson (IMP) for behavioural phenotypes is similar to an ongoing effort at Janelia Farm called the Fly Olympiad using the Rubin GAL4 collection described in Pfeiffer et al., 2008. Our collaboration with Simpson (Janelia) will allow us to solve problems common to this research approach (genetic reagents, imaging strategies, data management, behavioural assay development, etc.) and to compare results. While screening for slightly different phenotypes, we will be able to characterise GAL4 lines that may come out of our respective screens in greater detail. The task of the fellow will be to establish in Munich -Grunwald Kadow (MPIN)- a collection of five high-throughput behavioural assays developed by other members of the network: (i) CO2 innate avoidance assay based on a T-maze -Grunwald Kadow, (ii) simplified version of the detour paradigm, (iii) multisensory integration in a 4-arm maze -odour paired with taste -Grunwald Kadow, (iv) hygrotaxis, (v) preference between high and low sugar concentrations. The fellow will transfer assays (i) to (iv) to Janelia. She/he will conduct and/or oversee the screening efforts of the GAL4 collections with the assistance of personnel in the labs of Grunwald Kadow and Simpson (Janelia). She/he will also use calcium sensors (GCaMP) to functionally characterise the circuits labelled by the P[GAL4] lines associated with the most interesting behavioural phenotypes.
Title: New Assays to study sensory behaviours.
Goal: Development of a 4-D observation station for the analysis of fly behaviour in response to multimodal stimuli.
Methodology: The most popular behavioural assays measuring the response of flies to specific sensory signals are based on highly artificial paradigms. Thus far, this limitation has been necessary as it allows for the development of reproducible experiments. However, with the advent of high speed imaging and improved tracking software, it should be feasible to observe spontaneous behaviour of animals in response to changes in their sensory environment. The fellow will address this technical challenge by constructing an observation station, a FlyWorld, in which groups of flies can be monitored in 4D before, during and after the presentation of dynamical stimuli. The side walls of the box will be made by flat screens allowing the presentation of visual stimuli. In addition, LED lights will mimic the day/night cycle; devices embedded in the arena will deliver odorant and gustatory stimuli in a controlled way. Tracking software will extract the position and kinetic characteristics of the flies. FlyWorld will represent a general tool that can be adapted to the needs of each partner and their specific research questions.
Title: Novel methods for functional imaging
Goal: Developing a technological platform to monitor neuronal activity in unrestrained flies.
Methodology: We propose to develop a technological platform that will allow monitoring neuronal activity using bioluminescence of specific neuronal ensembles while larvae perform any given behaviour. By targeting the expression of the Ca2+ sensitive photoprotein GFP-Aequorin to specific neurons using the GAL4-UAS system, we will be able to monitor the activity of these neurons while the animal is freely behaving. Neuronal activity will be recorded by detecting single photons using a highly-sensitive photo-multiplier equipped with an infrared filter. In this way, only photons originating from Ca2+ changes in the targeted neurons will be detected by the photomultiplier. the Student will test and establish protocols for introducing the GFP-Aequorin substrate coelenterazine in D. melanogaster larvae in a simple, rapid and non-invasive way. He will test the feasibility and sensitivity of the proposed imaging setup by targeting the expression of GFP-Aequorin to the olfactory system and challenging the animal with different odours. Louis (CRG) will provide automated tracking software and the expertise on larval olfactory assays and behaviour.