Currently, more and more laboratories are acquiring the capability of simultaneously detecting th... more Currently, more and more laboratories are acquiring the capability of simultaneously detecting the extracellular activity of neurons in anaesthetized and awake animals by multielectrode recordings. In insects, multielectrode recordings are challenging due to the small size of the nervous system. Nevertheless, multielectrode recordings have been successfully established in brains of cockroaches, honeybees, fruit flies and grasshoppers to study sensory processing related to mechanosensation, olfaction, vision and audition. The number of neurons which can be recorded using such multielectrodes did not exceed 5 and likely depends on factors like recorded compartment of the neuron, impedance of the multielectrode, number of wires included in the multielectrode and threshold for spike detection. Signal-to-noise ratio (SNR) of the recordings obviously depends on the material and method used for the production of multielectrodes. To mark the location of the recording, different methods like current-driven copper deposition, labelling with fluorescent dye and electrocoagulation of nervous tissue are used. As expected, multielectrode recordings are more difficult in freely moving compared to restrained insects due to movement artifacts and requirement for fixed placement of the multielectrode at a particular recording site in the central nervous system (CNS). Specific characteristics of different preparations and sensory systems that include, disentangling spike collisions connected to auditory stimulation, increase in SNR after extended recording periods in olfactory systems and photoelectrical effects from compound eyes associated with visual stimulation, may require special attention and particular adaptations.
1Behaviour involving two or more individuals within the same species is known as social behaviour... more 1Behaviour involving two or more individuals within the same species is known as social behaviour. Sexual dimorphisms and environmental cues as well as age, experience and social hierarchy shape social behaviour. The study of this complex behaviour, however, has one essential boundary condition: the distance between individuals. Because social signals (e.g. acoustic, visual or olfactory) have limited reach the inter-individual distance is crucial for the correct transmission of such signals. In this study we present a newly developed assay to study group behaviour and inter-individual distance in Drosophila melanogaster. This assay consists of a circular observation space flanked by two automatic release devices that allow flies to enter individually. By releasing the flies one at a time, the observer can study different features of (intra-)group behaviour with different group compositions. Importantly, the observer can control (manually or through automatisation) the increase of gr...
Cytokine receptor like factor 3 (CRLF3) is a conserved cytokine receptor present in all major eum... more Cytokine receptor like factor 3 (CRLF3) is a conserved cytokine receptor present in all major eumetazoan taxa. Though vertebrate CRLF3 has recently been implied in the regulation of hematopoiesis, its ligand remained unidentified. CRLF3 shares structural similarity with receptors for other hematopoietic growth factors including erythropoietin, thrombopoietin and granulocyte colony-stimulating factor. Besides hematopoietic organs, these established hematopoietic cytokines and their receptors are also widely expressed in other tissues including the nervous system, where they regulate proliferation, differentiation, cell survival and other homeostatic processes. Previous studies identified insect CRLF3 as a neuroprotective receptor that can be activated by human recombinant erythropoietin, a widely accepted protective cytokine in vertebrate nervous systems. Epo’s erythropoietic functions mediated by classical Epo receptor are understood in great detail whereas Epo-mediated cytoprotecti...
The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian ner... more The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian nervous systems via activation of poorly characterized receptors that differ from the "classical" homodimeric Epo receptor expressed on erythroid progenitor cells. Epo genes have been identified in vertebrate species ranging from human to fish, suggesting that Epo signaling evolved earlier than the vertebrate lineage. Studies on insects (Locusta migratoria, Chorthippus biguttulus, Tribolium castaneum) revealed Epo-mediated neuroprotection and neuroregeneration. Recombinant human Epo (rhEpo) prevents apoptosis by binding to a janus kinase-associated receptor, stimulation of STAT transcription factors, and generation of factors that prevent the activation of proapoptotic caspases. Insect neurons were also protected by a neuroprotective but nonerythropoietic Epo splice variant, suggesting similarity with mammalian neuroprotective but not with homodimeric "classical" Epo receptors. Additionally, rhEpo promotes the regeneration of neurites in primary cultured insect brain neurons and after nerve crush in an in vivo preparation. In contrast to neuroprotective and regenerative effects shared with mammalian species, no evidence for a role of Epo signaling in the regulation of neuro- or gliogenesis was found in insects. Similar structural and functional characteristics of the Epo binding receptors, partly shared transduction pathways that prevent apoptosis and the functional implication in neuroprotective and neuroregenerative processes in both mammalian and insect species, suggest that Epo-like signaling was already established in their last common ancestor. Originally functioning as a tissue-protective response to unfavorable physiological situations, cell injury, and pathogen invasion, Epo was later adapted as a humoral regulator of erythropoiesis in the vertebrate lineage.
Cytokine receptor-like factor 3 (CRLF3) is a highly conserved but largely uncharacterized orphan ... more Cytokine receptor-like factor 3 (CRLF3) is a highly conserved but largely uncharacterized orphan cytokine receptor that shares structural similarity with vertebrate classical erythropoietin receptor. CRLF3-mediated neuroprotection in insects can be stimulated with human erythropoietin and involves partly similar anti-apoptotic mechanisms as erythropoietin-mediated neuroprotection in mammals. To identify potential mechanisms of CRLF3-mediated neuroprotection we studied the expression and function of acetylcholinesterase which promotes apoptosis in different cell types, including mammalian neurons. We exposed primary brain neurons from Locusta migratoria and Tribolium castaneum to apoptogenic stimuli and/or dsRNA to interfere with acetylcholinesterase gene expression and compared survival and/or acetylcholinesterase expression in the presence or absence of the CRLF3 ligand erythropoietin. Hypoxia increases both apoptotic cell death and expression of both acetylcholinesterase-coding ge...
General introduction Chapter 1: General Introduction 2 1.1 Communication and its sensory aspects ... more General introduction Chapter 1: General Introduction 2 1.1 Communication and its sensory aspects Communication is a very much fascinating thing. Its study has helped in the general understanding of motor and sensory systems, evolution, and speciation. A major appeal of studying communication is that a researcher can quantify how biologically important information can be coded in particular physical properties of a signal and then experimentally determine if the animals themselves use this information (Gerhardt and Huber 2002). The main use of sounds for vocal communication is widespread among vertebrates and invertebrates which range from mating calls in insects to speech in humans. Sound can transmit broader messages like species identity or narrow messages like the effective state of a caller (Schehka 2009). Communication is a key area of animal behavior because all social interactions among individuals are based on the exchange of information. For communication to occur, a sender has to encode information in a signal, which is then transmitted to a receiver (Shannon and Weaver 1949). Animals have evolved the most astounding ways to pass on messages, by using optical, acoustic, electric or chemical signals. Among them, acoustic signals serve a number of functions and are often part of social behavior. One of the key goals in research on acoustic communication is to explore the wide range of information conveyed in vocal signals. 1.2 Acoustic communication in insects Acoustic communication is widely spread among vertebrates but, among invertebrates, hearing and acoustic communication are well developed only in insects, in which they serve as detection of predators, the location of mates and of hosts (Pollack 2000). Insects offer several advantages as model systems for neuroethological studies, including robust behavior, easily accessible nervous system and uniquely identifiable neurons that permit one to frame general questions about the neural analysis of signals at the levels of single nerve cells (Nolen and Hoy 1984). Insects are good subjects for studies of the mechanisms underlying signal production and recognition and localization. In insects, interneurons that trigger sound-producing mechanisms have been characterized both anatomically and physiologically (Stumpner and Ronacher 1991). Moreover, the orchestrated activity of motor neurons, muscles or both that pattern acoustic signals has been described in detail (Gans 1973; Hedwig 1994; Heinrich and Elsner 1997a). Insects are also suitable for studying sensory
Neuroendocrine Regulation of Animal Vocalization, 2021
Abstract Acoustic communication in insects serves mate attraction, courtship, aggregation, compet... more Abstract Acoustic communication in insects serves mate attraction, courtship, aggregation, competition, territoriality, and predation and may inform a conspecific receiver about the physiological status of the sender. Acoustic signals are associated with particular behaviors and should only be performed in the correct context. This context is internally represented by neuroendocrinal signals. Hormones released from endocrine organs and neurosecretory regions establish or reconfigure neural circuits and determine general physiological states, which represent permissive requirements for the execution of a particular behavior that may include sound production. Neuromodulators alter the sensitivity of sensory and decision making premotor circuits to regulate the likelihood, specific pattern and intensity of sound production or other behaviors on a minute timescale. Neurotransmitters serve as immediate triggers for the initiation of sound production in response to actual sensory input and mediate the fine-tuned synaptic transmission in pattern-generating circuits. Different aspects of the neuroendocrinal regulation of acoustic sensory-to-motor processing have been studied in relatively few insect species, most intensively in grasshoppers, crickets, bushcrickets, honey bees, and fruit flies.
The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine recepto... more The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine receptor present in all major eumetazoan groups. Endogenous CRLF3 ligands have not been identified and the physiological responses mediated by mammalian CRLF3 are poorly characterized. Insect CRLF3 is activated by erythropoietin (Epo) and several related molecules that protect mammalian neurons from stress-induced apoptosis. However, insects neither express Epo nor “classical” Epo receptor. Cell-protective effects of insect hemolymph have been described for several species. In this study, we explored the possibility that the endogenous CRLF3 ligand is contained in locust hemolymph. PCR analyses confirmed expression ofcrfl3-transcripts in neurons and hemocytes ofLocusta migratoriaandTribolium castaneum. Survival of locust hemocytes in primary cultures was significantly increased by supplementation of culture medium with locust hemolymph serum. Locust primary neuron cultures were also protected b...
Traumatic brain injury causes progressive brain atrophy and cognitive decline. Surprisingly, an e... more Traumatic brain injury causes progressive brain atrophy and cognitive decline. Surprisingly, an early treatment with erythropoietin (EPO) prevents these consequences of secondary neurodegeneration, but the mechanisms have remained obscure. Here we show by advanced imaging and innovative analytical tools that recombinant human EPO, a clinically established and neuroprotective growth factor, dampens microglial activity, as visualized also in vivo by a strongly attenuated injury-induced cellular motility.
Apoptosis plays a major role in development, tissue renewal and the progression of degenerative d... more Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a pro-apoptotic function of acetylcholinesterase (AChE), particularly in the formation of the apoptosome and the degradation of nuclear DNA. While three AChE splice variants are present in mammals, invertebrates typically express two ache genes that code for a synaptically located protein and a protein with non-synaptic functions respectively. In order to investigate a potential contribution of AChE to apoptosis in insects, we selected the migratory locust Locusta migratoria. We established primary neuronal cultures of locust brains and characterized apoptosis progression in vitro. Dying neurons displayed typical characteristics of apoptosis, including caspase-activation, nuclear condensation and DNA fragmentation visualized by TUNEL staining. Addition of the AChE inhibitors neostigmine and territrem B reduced apoptotic cell d...
The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoi... more The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoietin receptor in locust neurons and emerged with the evolution of the eumetazoan nervous system. Human CRLF3 belongs to class I helical cytokine receptors that mediate pleiotropic cellular reactions to injury and diverse physiological challenges. It is expressed in various tissues including the central nervous system but its ligand remains unidentified. A CRLF3 ortholog in the holometabolous beetle Tribolium castaneum was recently shown to induce anti-apoptotic mechanisms upon stimulation with human recombinant erythropoietin. To test the hypothesis that CRLF3 represents an ancient cell-protective receptor for erythropoietin-like cytokines, we investigated its presence across metazoan species. Furthermore, we examined CRLF3 expression and function in the hemimetabolous insect Locusta migratoria. Phylogenetic analysis of CRLF3 sequences indicated that CRLF3 is absent in Porifera, Placozoa and Ctenophora, all lacking the traditional nervous system. However, it is present in all major eumetazoan groups ranging from cnidarians over protostomians to mammals. The CRLF3 sequence is highly conserved and abundant amongst vertebrates. In contrast, relatively few invertebrates express CRLF3 and these sequences show greater variability, suggesting frequent loss due to low functional importance. In L. migratoria, we identified the transcript Lm-crlf3 by RACE-PCR and detected its expression in locust brain, skeletal muscle and hemocytes. These findings correspond to the ubiquitous expression of crlf3 in mammalian tissues. We demonstrate that the sole addition of doublestranded RNA to the culture medium (called soaking RNA interference) specifically interferes with protein expression in locust primary brain cell cultures. This technique was used to knock down Lm-crlf3 expression and to abolish its physiological function. We confirmed that recombinant human erythropoietin rescues locust brain neurons from hypoxia-induced apoptosis and showed that this neuroprotective effect is absent after knocking down Lm-crlf3. Our results affirm the erythropoietin-induced neuroprotective
In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in ve... more In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in vertebrates, Erythropoietin (Epo) contributes to beneficial functions in a variety of non-hematopoietic tissues including the nervous system. Epo protects cells from apoptosis, reduces inflammatory responses and supports re-establishment of compromised functions by stimulating proliferation, migration and differentiation to compensate for lost or injured cells. Similar neuroprotective and regenerative functions of Epo have been described in the nervous systems of both vertebrates and invertebrates, indicating that tissue-protective Epo-like signaling has evolved prior to its erythropoietic function in the vertebrate lineage. Epo mediates its erythropoietic function through a homodimeric Epo receptor (EpoR) that is also widely expressed in the nervous system. However, identification of neuroprotective but non-erythropoietic Epo splice variants and Epo derivatives indicated the existence of other types of Epo receptors. In this review, we summarize evidence for potential Epo receptors that might mediate Epo's tissue-protective function in non-hematopoietic tissue, with focus on the nervous system. In particular, besides EpoR, we discuss three other potential neuroprotective Epo receptors: (1) a heteroreceptor consisting of EpoR and common beta receptor (βcR), (2) the Ephrin (Eph) B4 receptor and (3) the human orphan cytokine receptor-like factor 3 (CRLF3).
The genome of Drosophila melanogaster includes homologs to approximately one-third of the current... more The genome of Drosophila melanogaster includes homologs to approximately one-third of the currently known human disease genes. Flies and humans share many biological processes, including the principles of information processing by excitable neurons, synaptic transmission, and the chemical signals involved in intercellular communication. Studies on the molecular and behavioral impact of genetic risk factors of human neuro-developmental disorders [autism spectrum disorders (ASDs), schizophrenia, attention deficit hyperactivity disorders, and Tourette syndrome] increasingly use the well-studied social behavior of D. melanogaster, an organism that is amenable to a large variety of genetic manipulations. Neuroligins (Nlgs) are a family of phylogenetically conserved postsynaptic adhesion molecules present (among others) in nematodes, insects, and mammals. Impaired function of Nlgs (particularly of Nlg 3 and 4) has been associated with ASDs in humans and impaired social and communication behavior in mice. Making use of a set of behavioral and social assays, we, here, analyzed the impact of two Drosophila Nlgs, Dnlg2 and Dnlg4, which are differentially expressed at excitatory and inhibitory central nervous synapses, respectively. Both Nlgs seem to be associated with diurnal activity and social behavior. Even though deficiencies in Dnlg2 and Dnlg4 appeared to have no effects on sensory or motor systems, they differentially impacted on social interactions, suggesting that social behavior is distinctly regulated by these Nlgs.
We investigated brain regions - mostly neuropils - that process auditory information relevant for... more We investigated brain regions - mostly neuropils - that process auditory information relevant for the initiation of response songs of female grasshoppers Chorthippus biguttulus during bidirectional intraspecific acoustic communication. Male-female acoustic duets in the species Ch. biguttulus require the perception of sounds, their recognition as a species- and gender-specific signal and the initiation of commands that activate thoracic pattern generating circuits to drive the sound-producing stridulatory movements of the hind legs. To study sensory-to-motor processing during acoustic communication we used multielectrodes that allowed simultaneous recordings of acoustically stimulated electrical activity from several ascending auditory interneurons or local brain neurons and subsequent electrical stimulation of the recording site. Auditory activity was detected in the lateral protocerebrum (where most of the described ascending auditory interneurons terminate), in the superior medial protocerebrum and in the central complex, that has previously been implicated in the control of sound production. Neural responses to behaviorally attractive sound stimuli showed no or only poor correlation with behavioral responses. Current injections into the lateral protocerebrum, the central complex and the deuto-/tritocerebrum (close to the cerebro-cervical fascicles), but not into the superior medial protocerebrum, elicited species-typical stridulation with high success rate. Latencies and numbers of phrases produced by electrical stimulation were different between these brain regions. Our results indicate three brain regions (likely neuropils) where auditory activity can be detected with two of these regions being potentially involved in song initiation.
Neural networks : the official journal of the International Neural Network Society, Jan 23, 2016
Recent studies have demonstrated that Drosophila melanogaster (briefly Drosophila) can successful... more Recent studies have demonstrated that Drosophila melanogaster (briefly Drosophila) can successfully perform higher cognitive processes including second order olfactory conditioning. Understanding the neural mechanism of this behavior can help neuroscientists to unravel the principles of information processing in complex neural systems (e.g. the human brain) and to create efficient and robust robotic systems. In this work, we have developed a biologically-inspired spiking neural network which is able to execute both first and second order conditioning. Experimental studies demonstrated that volume signaling (e.g. by the gaseous transmitter nitric oxide) contributes to memory formation in vertebrates and invertebrates including insects. Based on the existing knowledge of odor encoding in Drosophila, the role of retrograde signaling in memory function, and the integration of synaptic and non-synaptic neural signaling, a neural system is implemented as Simulated fly. Simulated fly navig...
Currently, more and more laboratories are acquiring the capability of simultaneously detecting th... more Currently, more and more laboratories are acquiring the capability of simultaneously detecting the extracellular activity of neurons in anaesthetized and awake animals by multielectrode recordings. In insects, multielectrode recordings are challenging due to the small size of the nervous system. Nevertheless, multielectrode recordings have been successfully established in brains of cockroaches, honeybees, fruit flies and grasshoppers to study sensory processing related to mechanosensation, olfaction, vision and audition. The number of neurons which can be recorded using such multielectrodes did not exceed 5 and likely depends on factors like recorded compartment of the neuron, impedance of the multielectrode, number of wires included in the multielectrode and threshold for spike detection. Signal-to-noise ratio (SNR) of the recordings obviously depends on the material and method used for the production of multielectrodes. To mark the location of the recording, different methods like current-driven copper deposition, labelling with fluorescent dye and electrocoagulation of nervous tissue are used. As expected, multielectrode recordings are more difficult in freely moving compared to restrained insects due to movement artifacts and requirement for fixed placement of the multielectrode at a particular recording site in the central nervous system (CNS). Specific characteristics of different preparations and sensory systems that include, disentangling spike collisions connected to auditory stimulation, increase in SNR after extended recording periods in olfactory systems and photoelectrical effects from compound eyes associated with visual stimulation, may require special attention and particular adaptations.
1Behaviour involving two or more individuals within the same species is known as social behaviour... more 1Behaviour involving two or more individuals within the same species is known as social behaviour. Sexual dimorphisms and environmental cues as well as age, experience and social hierarchy shape social behaviour. The study of this complex behaviour, however, has one essential boundary condition: the distance between individuals. Because social signals (e.g. acoustic, visual or olfactory) have limited reach the inter-individual distance is crucial for the correct transmission of such signals. In this study we present a newly developed assay to study group behaviour and inter-individual distance in Drosophila melanogaster. This assay consists of a circular observation space flanked by two automatic release devices that allow flies to enter individually. By releasing the flies one at a time, the observer can study different features of (intra-)group behaviour with different group compositions. Importantly, the observer can control (manually or through automatisation) the increase of gr...
Cytokine receptor like factor 3 (CRLF3) is a conserved cytokine receptor present in all major eum... more Cytokine receptor like factor 3 (CRLF3) is a conserved cytokine receptor present in all major eumetazoan taxa. Though vertebrate CRLF3 has recently been implied in the regulation of hematopoiesis, its ligand remained unidentified. CRLF3 shares structural similarity with receptors for other hematopoietic growth factors including erythropoietin, thrombopoietin and granulocyte colony-stimulating factor. Besides hematopoietic organs, these established hematopoietic cytokines and their receptors are also widely expressed in other tissues including the nervous system, where they regulate proliferation, differentiation, cell survival and other homeostatic processes. Previous studies identified insect CRLF3 as a neuroprotective receptor that can be activated by human recombinant erythropoietin, a widely accepted protective cytokine in vertebrate nervous systems. Epo’s erythropoietic functions mediated by classical Epo receptor are understood in great detail whereas Epo-mediated cytoprotecti...
The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian ner... more The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian nervous systems via activation of poorly characterized receptors that differ from the "classical" homodimeric Epo receptor expressed on erythroid progenitor cells. Epo genes have been identified in vertebrate species ranging from human to fish, suggesting that Epo signaling evolved earlier than the vertebrate lineage. Studies on insects (Locusta migratoria, Chorthippus biguttulus, Tribolium castaneum) revealed Epo-mediated neuroprotection and neuroregeneration. Recombinant human Epo (rhEpo) prevents apoptosis by binding to a janus kinase-associated receptor, stimulation of STAT transcription factors, and generation of factors that prevent the activation of proapoptotic caspases. Insect neurons were also protected by a neuroprotective but nonerythropoietic Epo splice variant, suggesting similarity with mammalian neuroprotective but not with homodimeric "classical" Epo receptors. Additionally, rhEpo promotes the regeneration of neurites in primary cultured insect brain neurons and after nerve crush in an in vivo preparation. In contrast to neuroprotective and regenerative effects shared with mammalian species, no evidence for a role of Epo signaling in the regulation of neuro- or gliogenesis was found in insects. Similar structural and functional characteristics of the Epo binding receptors, partly shared transduction pathways that prevent apoptosis and the functional implication in neuroprotective and neuroregenerative processes in both mammalian and insect species, suggest that Epo-like signaling was already established in their last common ancestor. Originally functioning as a tissue-protective response to unfavorable physiological situations, cell injury, and pathogen invasion, Epo was later adapted as a humoral regulator of erythropoiesis in the vertebrate lineage.
Cytokine receptor-like factor 3 (CRLF3) is a highly conserved but largely uncharacterized orphan ... more Cytokine receptor-like factor 3 (CRLF3) is a highly conserved but largely uncharacterized orphan cytokine receptor that shares structural similarity with vertebrate classical erythropoietin receptor. CRLF3-mediated neuroprotection in insects can be stimulated with human erythropoietin and involves partly similar anti-apoptotic mechanisms as erythropoietin-mediated neuroprotection in mammals. To identify potential mechanisms of CRLF3-mediated neuroprotection we studied the expression and function of acetylcholinesterase which promotes apoptosis in different cell types, including mammalian neurons. We exposed primary brain neurons from Locusta migratoria and Tribolium castaneum to apoptogenic stimuli and/or dsRNA to interfere with acetylcholinesterase gene expression and compared survival and/or acetylcholinesterase expression in the presence or absence of the CRLF3 ligand erythropoietin. Hypoxia increases both apoptotic cell death and expression of both acetylcholinesterase-coding ge...
General introduction Chapter 1: General Introduction 2 1.1 Communication and its sensory aspects ... more General introduction Chapter 1: General Introduction 2 1.1 Communication and its sensory aspects Communication is a very much fascinating thing. Its study has helped in the general understanding of motor and sensory systems, evolution, and speciation. A major appeal of studying communication is that a researcher can quantify how biologically important information can be coded in particular physical properties of a signal and then experimentally determine if the animals themselves use this information (Gerhardt and Huber 2002). The main use of sounds for vocal communication is widespread among vertebrates and invertebrates which range from mating calls in insects to speech in humans. Sound can transmit broader messages like species identity or narrow messages like the effective state of a caller (Schehka 2009). Communication is a key area of animal behavior because all social interactions among individuals are based on the exchange of information. For communication to occur, a sender has to encode information in a signal, which is then transmitted to a receiver (Shannon and Weaver 1949). Animals have evolved the most astounding ways to pass on messages, by using optical, acoustic, electric or chemical signals. Among them, acoustic signals serve a number of functions and are often part of social behavior. One of the key goals in research on acoustic communication is to explore the wide range of information conveyed in vocal signals. 1.2 Acoustic communication in insects Acoustic communication is widely spread among vertebrates but, among invertebrates, hearing and acoustic communication are well developed only in insects, in which they serve as detection of predators, the location of mates and of hosts (Pollack 2000). Insects offer several advantages as model systems for neuroethological studies, including robust behavior, easily accessible nervous system and uniquely identifiable neurons that permit one to frame general questions about the neural analysis of signals at the levels of single nerve cells (Nolen and Hoy 1984). Insects are good subjects for studies of the mechanisms underlying signal production and recognition and localization. In insects, interneurons that trigger sound-producing mechanisms have been characterized both anatomically and physiologically (Stumpner and Ronacher 1991). Moreover, the orchestrated activity of motor neurons, muscles or both that pattern acoustic signals has been described in detail (Gans 1973; Hedwig 1994; Heinrich and Elsner 1997a). Insects are also suitable for studying sensory
Neuroendocrine Regulation of Animal Vocalization, 2021
Abstract Acoustic communication in insects serves mate attraction, courtship, aggregation, compet... more Abstract Acoustic communication in insects serves mate attraction, courtship, aggregation, competition, territoriality, and predation and may inform a conspecific receiver about the physiological status of the sender. Acoustic signals are associated with particular behaviors and should only be performed in the correct context. This context is internally represented by neuroendocrinal signals. Hormones released from endocrine organs and neurosecretory regions establish or reconfigure neural circuits and determine general physiological states, which represent permissive requirements for the execution of a particular behavior that may include sound production. Neuromodulators alter the sensitivity of sensory and decision making premotor circuits to regulate the likelihood, specific pattern and intensity of sound production or other behaviors on a minute timescale. Neurotransmitters serve as immediate triggers for the initiation of sound production in response to actual sensory input and mediate the fine-tuned synaptic transmission in pattern-generating circuits. Different aspects of the neuroendocrinal regulation of acoustic sensory-to-motor processing have been studied in relatively few insect species, most intensively in grasshoppers, crickets, bushcrickets, honey bees, and fruit flies.
The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine recepto... more The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine receptor present in all major eumetazoan groups. Endogenous CRLF3 ligands have not been identified and the physiological responses mediated by mammalian CRLF3 are poorly characterized. Insect CRLF3 is activated by erythropoietin (Epo) and several related molecules that protect mammalian neurons from stress-induced apoptosis. However, insects neither express Epo nor “classical” Epo receptor. Cell-protective effects of insect hemolymph have been described for several species. In this study, we explored the possibility that the endogenous CRLF3 ligand is contained in locust hemolymph. PCR analyses confirmed expression ofcrfl3-transcripts in neurons and hemocytes ofLocusta migratoriaandTribolium castaneum. Survival of locust hemocytes in primary cultures was significantly increased by supplementation of culture medium with locust hemolymph serum. Locust primary neuron cultures were also protected b...
Traumatic brain injury causes progressive brain atrophy and cognitive decline. Surprisingly, an e... more Traumatic brain injury causes progressive brain atrophy and cognitive decline. Surprisingly, an early treatment with erythropoietin (EPO) prevents these consequences of secondary neurodegeneration, but the mechanisms have remained obscure. Here we show by advanced imaging and innovative analytical tools that recombinant human EPO, a clinically established and neuroprotective growth factor, dampens microglial activity, as visualized also in vivo by a strongly attenuated injury-induced cellular motility.
Apoptosis plays a major role in development, tissue renewal and the progression of degenerative d... more Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a pro-apoptotic function of acetylcholinesterase (AChE), particularly in the formation of the apoptosome and the degradation of nuclear DNA. While three AChE splice variants are present in mammals, invertebrates typically express two ache genes that code for a synaptically located protein and a protein with non-synaptic functions respectively. In order to investigate a potential contribution of AChE to apoptosis in insects, we selected the migratory locust Locusta migratoria. We established primary neuronal cultures of locust brains and characterized apoptosis progression in vitro. Dying neurons displayed typical characteristics of apoptosis, including caspase-activation, nuclear condensation and DNA fragmentation visualized by TUNEL staining. Addition of the AChE inhibitors neostigmine and territrem B reduced apoptotic cell d...
The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoi... more The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoietin receptor in locust neurons and emerged with the evolution of the eumetazoan nervous system. Human CRLF3 belongs to class I helical cytokine receptors that mediate pleiotropic cellular reactions to injury and diverse physiological challenges. It is expressed in various tissues including the central nervous system but its ligand remains unidentified. A CRLF3 ortholog in the holometabolous beetle Tribolium castaneum was recently shown to induce anti-apoptotic mechanisms upon stimulation with human recombinant erythropoietin. To test the hypothesis that CRLF3 represents an ancient cell-protective receptor for erythropoietin-like cytokines, we investigated its presence across metazoan species. Furthermore, we examined CRLF3 expression and function in the hemimetabolous insect Locusta migratoria. Phylogenetic analysis of CRLF3 sequences indicated that CRLF3 is absent in Porifera, Placozoa and Ctenophora, all lacking the traditional nervous system. However, it is present in all major eumetazoan groups ranging from cnidarians over protostomians to mammals. The CRLF3 sequence is highly conserved and abundant amongst vertebrates. In contrast, relatively few invertebrates express CRLF3 and these sequences show greater variability, suggesting frequent loss due to low functional importance. In L. migratoria, we identified the transcript Lm-crlf3 by RACE-PCR and detected its expression in locust brain, skeletal muscle and hemocytes. These findings correspond to the ubiquitous expression of crlf3 in mammalian tissues. We demonstrate that the sole addition of doublestranded RNA to the culture medium (called soaking RNA interference) specifically interferes with protein expression in locust primary brain cell cultures. This technique was used to knock down Lm-crlf3 expression and to abolish its physiological function. We confirmed that recombinant human erythropoietin rescues locust brain neurons from hypoxia-induced apoptosis and showed that this neuroprotective effect is absent after knocking down Lm-crlf3. Our results affirm the erythropoietin-induced neuroprotective
In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in ve... more In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in vertebrates, Erythropoietin (Epo) contributes to beneficial functions in a variety of non-hematopoietic tissues including the nervous system. Epo protects cells from apoptosis, reduces inflammatory responses and supports re-establishment of compromised functions by stimulating proliferation, migration and differentiation to compensate for lost or injured cells. Similar neuroprotective and regenerative functions of Epo have been described in the nervous systems of both vertebrates and invertebrates, indicating that tissue-protective Epo-like signaling has evolved prior to its erythropoietic function in the vertebrate lineage. Epo mediates its erythropoietic function through a homodimeric Epo receptor (EpoR) that is also widely expressed in the nervous system. However, identification of neuroprotective but non-erythropoietic Epo splice variants and Epo derivatives indicated the existence of other types of Epo receptors. In this review, we summarize evidence for potential Epo receptors that might mediate Epo's tissue-protective function in non-hematopoietic tissue, with focus on the nervous system. In particular, besides EpoR, we discuss three other potential neuroprotective Epo receptors: (1) a heteroreceptor consisting of EpoR and common beta receptor (βcR), (2) the Ephrin (Eph) B4 receptor and (3) the human orphan cytokine receptor-like factor 3 (CRLF3).
The genome of Drosophila melanogaster includes homologs to approximately one-third of the current... more The genome of Drosophila melanogaster includes homologs to approximately one-third of the currently known human disease genes. Flies and humans share many biological processes, including the principles of information processing by excitable neurons, synaptic transmission, and the chemical signals involved in intercellular communication. Studies on the molecular and behavioral impact of genetic risk factors of human neuro-developmental disorders [autism spectrum disorders (ASDs), schizophrenia, attention deficit hyperactivity disorders, and Tourette syndrome] increasingly use the well-studied social behavior of D. melanogaster, an organism that is amenable to a large variety of genetic manipulations. Neuroligins (Nlgs) are a family of phylogenetically conserved postsynaptic adhesion molecules present (among others) in nematodes, insects, and mammals. Impaired function of Nlgs (particularly of Nlg 3 and 4) has been associated with ASDs in humans and impaired social and communication behavior in mice. Making use of a set of behavioral and social assays, we, here, analyzed the impact of two Drosophila Nlgs, Dnlg2 and Dnlg4, which are differentially expressed at excitatory and inhibitory central nervous synapses, respectively. Both Nlgs seem to be associated with diurnal activity and social behavior. Even though deficiencies in Dnlg2 and Dnlg4 appeared to have no effects on sensory or motor systems, they differentially impacted on social interactions, suggesting that social behavior is distinctly regulated by these Nlgs.
We investigated brain regions - mostly neuropils - that process auditory information relevant for... more We investigated brain regions - mostly neuropils - that process auditory information relevant for the initiation of response songs of female grasshoppers Chorthippus biguttulus during bidirectional intraspecific acoustic communication. Male-female acoustic duets in the species Ch. biguttulus require the perception of sounds, their recognition as a species- and gender-specific signal and the initiation of commands that activate thoracic pattern generating circuits to drive the sound-producing stridulatory movements of the hind legs. To study sensory-to-motor processing during acoustic communication we used multielectrodes that allowed simultaneous recordings of acoustically stimulated electrical activity from several ascending auditory interneurons or local brain neurons and subsequent electrical stimulation of the recording site. Auditory activity was detected in the lateral protocerebrum (where most of the described ascending auditory interneurons terminate), in the superior medial protocerebrum and in the central complex, that has previously been implicated in the control of sound production. Neural responses to behaviorally attractive sound stimuli showed no or only poor correlation with behavioral responses. Current injections into the lateral protocerebrum, the central complex and the deuto-/tritocerebrum (close to the cerebro-cervical fascicles), but not into the superior medial protocerebrum, elicited species-typical stridulation with high success rate. Latencies and numbers of phrases produced by electrical stimulation were different between these brain regions. Our results indicate three brain regions (likely neuropils) where auditory activity can be detected with two of these regions being potentially involved in song initiation.
Neural networks : the official journal of the International Neural Network Society, Jan 23, 2016
Recent studies have demonstrated that Drosophila melanogaster (briefly Drosophila) can successful... more Recent studies have demonstrated that Drosophila melanogaster (briefly Drosophila) can successfully perform higher cognitive processes including second order olfactory conditioning. Understanding the neural mechanism of this behavior can help neuroscientists to unravel the principles of information processing in complex neural systems (e.g. the human brain) and to create efficient and robust robotic systems. In this work, we have developed a biologically-inspired spiking neural network which is able to execute both first and second order conditioning. Experimental studies demonstrated that volume signaling (e.g. by the gaseous transmitter nitric oxide) contributes to memory formation in vertebrates and invertebrates including insects. Based on the existing knowledge of odor encoding in Drosophila, the role of retrograde signaling in memory function, and the integration of synaptic and non-synaptic neural signaling, a neural system is implemented as Simulated fly. Simulated fly navig...
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Papers by Ralf Heinrich