Biology subjects

Herlitze, S.

Publications and source records attributed to Herlitze, S..

13 recordsLinked to original sources

bioRxiv2026

Functional relevance of mobile and clustered CaV2.1 channels in central synapses

Reliable neurotransmitter release critically depends on the spatial relationship between voltage- gated calcium channels (VGCCs) and presynaptic release sites. Single particle tracking of endogenous CaV2.1 channels at glutamatergic synapses of hippocampal neurons revealed that apart from CaV2.1 channels aggregated in stable nanodomain clusters, a substantial fraction of Cav2.1 channels remained mobile, raising the question of whether these dispersed channels contribute to synaptic function. Mathematical modelling predicted that dispersed Cav2.1 channels cooperatively enhance release reliability. Upon repetitive stimulation, mobile CaV2.1 channels enable alternative use of release sites and thereby reduce the probability of failed presynaptic release. Both optogenetic immobilisation of CaV2.1 channels per se or activation of GABAB receptors (GABABRs) alone increase the failure rate and can lead to synaptic silencing. However, optogenetic clustering CaV2.1 channels prior to GABABR activation increases the fraction of synapses that remain active even in presence of GABABR agonist. The contribution of mobile channels to reliable neurotransmitter release is frequency-dependent and is minor at stimulation frequencies 1 Hz but becomes strong at frequencies over 10 Hz. These results demonstrate that mobile presynaptic CaV2.1 channels increase the frequency range of synaptic transmission but are particularly sensitive to metabotropic GABABR-mediated inhibition in glutamatergic hippocampal synapses.

neuroscience↗

bioRxiv2025

Ectopic expression of two cone opsins in mouse RGCs results in opposite responses to light stimulation, likely due to differential G protein activation

Retinitis pigmentosa, a leading cause of inherited blindness, results in photoreceptor degeneration that current optogenetic approaches aim to address through microbial opsin expression in retinal ganglion cells (RGCs). While these microbial proteins restore light sensitivity, their clinical potential remains limited by low light sensitivity and immunogenicity risks. Recent efforts have focused on vertebrate opsins as safer alternatives, with mid-wavelength cone opsin (MW-opsin) demonstrating RGC depolarization via endogenous G-protein signaling. In this study, we reveal a surprising divergence in signaling outcomes of expressing short-wavelength mouse cone opsin (Opn1sw) in RGCs of blind mice. Using multielectrode array recordings and whole-cell patch clamping, we demonstrate that Opn1sw induces membrane hyperpolarization in RGCs - a stark contrast to MW-opsins depolarizing effects. This unexpected inversion suggests differential engagement of intracellular signaling pathways, potentially stemming from distinct G-protein coupling preferences. Comparative analysis of native G-protein expression profiles in RGCs versus cone photoreceptors supports this hypothesis, revealing mismatches that may explain ectopic opsin behavior. Our findings challenge the assumption of conserved opsin signaling across spectral subtypes and cell types, highlighting critical gaps in understanding vertebrate opsin-G protein interactions in non-native cellular environments. This discovery points to the necessity of systematic characterization of opsin signaling networks in target retinal cells, a prerequisite for engineering optimized optogenetic tools that reliably produce desired electrophysiological outcomes. By establishing spectral subtype-dependent signaling divergence, our work redefines parameters for developing next-generation vision restoration therapies.

neuroscience↗

bioRxiv2025

Feeling the noise: Ascidians detect substrate-borne vibrations, not pressure waves

Marine anthropogenic noise pollution has risen in recent decades, driving interest in its ecological effects. While research has focused on mammals and fish, marine invertebrates remain largely understudied despite their ecological importance. This study explored sound perception in the benthic ascidian Halocynthia papillosa, assessing whether it detects acoustic signals via waterborne pressure waves or substrate vibrations. Field and laboratory experiments exposed H. papillosa to frequencies from 50-1500 Hz. Contraction responses occurred at 100 Hz, 200 Hz, and 600 Hz when played through a waterproof speaker that produced both, sound pressure and substrate vibration. In a controlled laboratory setup, only substrate vibrations triggered contractions, while pure sound pressure up to 130 dB re 1 {micro}Pa elicited no response. Repeated exposure led to habituation, reducing contraction amplitude and relaxation time. These findings indicate that ascidians rely on mechanoreception, underscoring the overlooked impact of substrate vibrations from marine noise and the necessity to reconsider study design when investigating effects of marine noise on benthic organisms.

zoology↗

bioRxiv2025

Constitutive activity of the inhibitory G protein pathway mediated by non-visual opsin Opn7b reduces cFos activity in stress and fear circuits and modulates avoidance behavior

Constitutive activity of G protein-coupled receptors (GPCRs) plays an important role in brain function and disease including neurodegenerative and psychiatric disorders. The non-visual opsin Opn7b is a constitutively active Gi/o coupled GPCR which has been used to synchronize neuronal networks. Here we show that expression of Opn7b in the bed nucleus of the stria terminalis and the ventral tegmental area, two interconnected brain areas involved in modulating fear and stress responses, reduces the number of cFos positive neurons and modulates avoidance behavior in mice. Thus, by constitutively activating the Gi/o pathway Opn7b can be used as a tool to reduce cFos expression and to link cFos-expressing neurons to network- and pathway-specific behavior.

neuroscience↗

bioRxiv2025

Achieving cell-type specific transduction with adeno-associated viral vectors in pigeons

Birds are valuable models for studying learning, cognition, song, and vision, yet tools for controlling and recording brain activity with millisecond precision remain underutilized in avian research. Advances in methods such as chemogenetics, optogenetics, and in vivo imaging have transformed rodent studies but require gene delivery techniques, like adeno-associated viruses (AAVs), in non-transgenic species. This study validates AAV tools for precise gene expression in pigeons. We identified AAV8 as a highly effective vector, demonstrating strong neuronal tropism and anterograde/retrograde transgene expression, while AAVretro was ineffective. The CaMKII promoter and mDLX enhancer enabled cell-type-specific expression, targeting predominantly excitatory and inhibitory neurons, respectively. Additionally, we established proof of concept for the expression of NpHR (a chloride pump) and demonstrated the functionality of conditional gene expression systems, including Cre/loxP and Tet-On/Tet-Off. These advancements expand the genetic toolkit for pigeons, facilitating precise manipulation of neural circuits and enabling future studies on complex avian behaviors and brain functions. By bridging molecular tools and avian neuroscience, this work paves the way for comparative and translational research, offering insights into the neural basis of cognition and sensory processing in birds.

neuroscience↗

bioRxiv2025

Multimodal characterization and optogenetic potential of the bistable Gi/o-coupled vertebrate ancient opsin from the flashlight fish Anomalops katoptron

Vertebrate ancient long opsin, or VAL opsin, is a light-sensitive protein that is found within and outside the visual system in vertebrates. In accordance with its wide distribution in the retina, brain, testis and skin, VAL is suggested to play a role in light-dependent physiological processes that are beyond vision. However, many aspects of the physiological properties and specific functions of VAL remain unclear. Here we identified and characterized the VAL opsin from the flashlight fish Anomalops katoptron (AkVAL) and show that this opsin is bistable and reversibly converts between active and inactive states by responding to cycles of green and blue/UV lights. We further show that AkVAL couples to the Gi/o pathway and controls the activity of GIRK channels in a bistable manner. In line with this, we demonstrated that AkVAL modulates neuronal activity in cerebellar Purkinje cells, where neuronal activity is reduced by UV/blue light and increased by green/red light illumination. In addition, upon the in vivo expression of AkVAL in neurons innervating body muscles of Caenorhabditis elegans the worms body movement can be bidirectionally controlled altering blue/UV and green illuminations. These data highlight the potential of AkVAL as an optogenetic tool to control cells in vitro and in vivo, in a bistable manner.

neuroscience↗

bioRxiv2025

Guiding G protein signaling by target enhancement of GPCRs

Activation of G protein coupled receptors coupling to the Gi/o pathway leads to the activation of G protein-activated inward rectifier potassium channels (GIRK) in a fast membrane-delimited manner in excitable cells. Activation of GIRK causes the hyperpolarization of the cell membrane, where hyperpolarization is dependent on te availability of Gi/o coupled GPCRs and GIRK. In particular, in optogenetic and chemogenetic experiments neuronal silencing depends on downstream targets of Gi/o-coupled GPCRs. To selectively enhance Gi/o mediated GIRK currents, we created expression cassettes consisting of a homomer forming GIRK subunit and various light-activated Gi/o-coupled GPCRs (Melanopsin, Long-wave-sensitive opsin 1, Parapinopsin or Opsin 7b). We demonstrate that light-activation of the GIRK/GPCR constructs induces robust GIRK currents in human embryonic kidney 293 cells, cardiomyocytes and cerebellar Purkinje cells and changes the net effect of G protein signaling of the promiscuous Opn4L from a Gq/11 mediated excitation towards an Gi/o mediated inhibition. Thus, our tools enhance target selectivity and improve optogenetic control of the Gi/o pathway by light in excitable cells.

neuroscience↗

bioRxiv2024

Correlation between bioluminescent blinks and swimming behavior in the splitfin flashlight fish Anomalops katoptron

The light organs of the splitfin flashlight fish Anomalops katoptron are necessary for schooling behavior, to determine nearest neighbor distance, and to feed on zooplankton under dim light conditions. Each behavior is coupled to context-dependent blink frequencies and can be regulated via mechanical occlusion of light organs. During shoaling in the laboratory individuals show moderate blink frequencies around 100 blinks per minute. In this study, we correlated bioluminescent blinks with the spatio-temporal dynamics of swimming profiles in three dimensions, using a stereoscopic, infrared camera system. Groups of flashlight fish showed intermediate levels of polarization and distances to the group centroid. Individuals showed higher swimming speeds and curved swimming profiles during light organ occlusion. The largest changes in swimming direction occurred when darkening the light organs. Before A. katoptron exposed light organs again, they adapted a nearly straight movement direction. Light organs create a strong contrast against the background. Therefore, a close combination of light signals and movement is crucial to the behavior of A. katoptron.

animal behavior and cognition↗

bioRxiv2023

Synaptic plasticity in the medial preoptic area of male mice encodes social experiences with female and regulates behavior toward young

A dramatic shift from aggressive infanticidal to paternal behaviors is an essential event for male mice after mating. While the central part of the medial preoptic area (cMPOA) has been shown to critically mediate the paternal behaviors in mice, how this brain region becomes activated by mating and subsequent interaction with pups has not been investigated. Here, we demonstrate that the reduction in inhibitory synaptic strength towards the cMPOA provided by posterior-dorsal medial amygdala (MePD) neurons is a key event for the post-mating behavioral shift in males. Consistent with this, we found optogenetic disinhibition of MeCartpt to the cMPOA synapses reduces male aggression towards pups. The cMPOA of paternal mice mediated pup-induced neural plastic changes in the bed nucleus of the stria terminalis. These findings provide possible functions of cMPOA neural circuits required for the reception to young in male mice.

zoology↗

bioRxiv2023

New observations of fluorescent organisms in the Banda Sea and in the Red Sea

Fluorescence is a widespread phenomenon found in animals, bacteria, fungi, and plants. In marine environments fluorescence has been proposed to play a role in physiological and behavioral responses. Many fluorescent proteins and other molecules have been described in jellyfish, corals, and fish. Here we describe fluorescence in marine species, which we observed and photographed during night dives in the Banda Sea, Indonesia, and in the Red Sea, Egypt. Among various phyla we found fluorescence in sponges, molluscs, tunicates, and fish. Our study extends the knowledge on how many different organisms fluoresce in marine environments. We describe the occurrence of fluorescence in 27 species, in which fluorescence has not been described yet in peer-reviewed literature. It especially extends the knowledge beyond Scleractinia, the so far best described taxon regarding diversity in fluorescent proteins.

zoology↗

bioRxiv2022

Constitutive 5-HT2C receptor knock-out facilitates fear extinction through altered activity of a dorsal raphe-bed nucleus of the stria terminalis pathway

Serotonin 2C receptors (5-HT2CRs) are widely distributed throughout the brain and are strongly implicated in the pathophysiology of anxiety disorders such as post-traumatic stress disorder (PTSD). Although in recent years, a considerable amount of evidence supports 5-HT2CRs facilitating effect on anxiety behavior, the involvement in learned fear responses and fear extinction is rather unexplored. Here we used a 5-HT2CR knock-out mouse line (2CKO) to gain new insights into the involvement of 5-HT2CRs in the neuronal fear circuitry. Using a cued fear conditioning paradigm, our results revealed that global loss of 5-HT2CRs exclusively accelerates fear extinction, without affecting fear acquisition and fear expression. To investigate the neuronal substrates underlying the extinction enhancing effect, we mapped the immediate-early gene product cFos, a marker for neuronal activity, in the dorsal raphe nucleus (DRN), amygdala and bed nucleus of the stria terminalis (BNST). Surprisingly, besides extinction-associated changes, our results revealed alterations in neuronal activity even under basal home cage conditions in specific subregions of the DRN and the BNST in 2CKO mice. Neuronal activity in the dorsal BNST was shifted in an extinction-supporting direction due to 5-HT2CR knock-out. Finally, the assessment of DRN-BNST connectivity using antero- and retrograde tracing techniques uncovered a discrete serotonergic DRC-BNSTad pathway showing increased activity in 2CKO mice. Thus, our results provide new insights for the fear extinction network by revealing a specific serotonergic DRC-BNSTad pathway underlying a 5-HT2CR-sensitive mechanism with high significance in the treatment of PTSD.

neuroscience↗

bioRxiv2020

Social signaling via bioluminescent blinks drives schooling behavior in the flashlight fish Anomalops katoptron

The bioluminescent flashlight fish Anomalops katoptron live in schools of several hundred specimens. To understand how flashlight fish, integrate bioluminescent signaling into their schooling behavior, we analyzed movement profiles and blink frequencies. Isolated specimen of A. katoptron show a high motivation to align with fixed or moving artificial light organs. Depending on presented frequencies A. katoptron responds with a reduction in swimming speed and its own blink frequency. Higher presented blink frequencies reduce the nearest neighbor distance. In the natural environment A. katoptron is changing its blink frequencies and nearest neighbor distance in a context specific manner. Blink frequencies are increased from day to night and during avoidance behavior, while nearest neighbor distance is decreased with increasing blink frequencies. A. katoptron changes its blink frequencies by modifying light organ occlusion. Our results suggest that visually transmitted information via specific blink patterns determine intraspecific communication and group cohesion in schooling A. katoptron.Competing Interest StatementThe authors have declared no competing interest.View Full Text

animal behavior and cognition↗

bioRxiv2018

Subtraction and division of visual cortical population responses by the serotonergic system

Normalization is a fundamental operation throughout neuronal systems to adjust dynamic range. In the visual cortex various cell circuits have been identified that provide the substrate for such a canonical function, but how these circuits are orchestrated remains unclear. Here we suggest the serotonergic (5-HT) system as another player involved in normalization. 5-HT receptors of different classes are co-distributed across different cortical cell types, but their individual contribution to cortical population responses is unknown. We combined wide-field calcium imaging of primary visual cortex (V1) with optogenetic stimulation of 5-HT neurons in mice dorsal raphe nucleus (DRN) -- the major hub for widespread release of serotonin across cortex -- in combination with selective 5-HT receptor blockers. While inhibitory (5-HT1A) receptors accounted for subtractive suppression of spontaneous activity, depolarizing (5-HT2A) receptors promoted divisive suppression of response gain. Added linearly, these components led to normalization of population responses over a range of visual contrasts.

neuroscience↗