Biology subjects

Romano, V.

Publications and source records attributed to Romano, V..

10 recordsLinked to original sources

bioRxiv2026

A Dipolar Photoswitch Modulates Bacterial Membrane Potential and Reveals Context-dependent Bioelectrical Circuitry

Dynamic bioelectric signalling in bacteria regulates physiology and collective behaviours, yet tools to perturb microbial membrane voltage with high spatiotemporal control remain limited. Here we introduce MTP2, a non-genetic, membrane-targeting azobenzene photoswitch that enables optical modulation of bacterial membrane potential by tuning interfacial electrostatics in Bacillus subtilis. MTP2 associates strongly with the cell envelope and shifts the resting potential to more negative values in the dark, while 470-nm illumination evokes a robust, reversible depolarization at the single-cell level. Although MTP2 photoisomerization is ultrafast (picoseconds), the voltage waveforms unfold over seconds to minutes, indicating that the response is set by homeostatic ion transport rather than by MTP2 photochemistry. Genetic and pharmacological perturbations show that K+ conductance, Cl--sensitive pathways, and active transport reshape the amplitude, kinetics and even polarity of the optical response, revealing a context-dependent interplay between a passive molecular perturbation and endogenous bioelectric circuitry. As a functional proof of concept, kanamycin efficacy co-varies with the optically tuned voltage state. Together, these results establish MTP2 as a reversible chemical optostimulator for probing and controlling microbial electrophysiology.

microbiology↗

bioRxiv2026

An Agent-Based Model of Protein Polymerization Dynamics: Focus on the Actin System

Actin polymerization is a critical cellular process involved in a wide range of activities, from cell motility to cytokinesis. The complex behavior of this molecular system, resulting in three different phases (i.e., nucleation, elongation, and steady state) is clear by looking at the way these dynamics emerge from a large number of interactions between different proteins, regulatory elements, and signaling pathways. In this article, we present an agent-based model of actin polymerization dynamics implemented with the NetLogo simulation platform and focus on the time evolution of actin filaments length distribution in two dimensions starting from a pool of free G-actin monomers. Stochastic simulations were able to reproduce all main steps of the polymerization process in vitro, as well as two emerging patterns which have been previously discovered using alternative approaches, namely global treadmilling of F-actin filaments and competition between nucleation and elongation. The ability of the model to replicate relevant theoretical and experimental findings makes this new tool suitable for simulating complex molecular mechanisms by manipulating a limited set of parameters.

systems biology↗

bioRxiv2025

Pattern separation in cerebellar-targeted whisking pre-motor nuclei

The cerebellar output can trigger whisker movement through indirect projections that pass via several brainstem pre-motor nuclei before reaching the facial nucleus, which directly controls whisker movements in rodents. Although the central pattern generator function of the intermediate reticular formation has been recently clarified, the roles of the other whisker pre-motor nuclei remain unclear. Here, we set out to compare the whisker movement kinematics of the main pre-motor whisker nuclei connecting the cerebellum and the facial nucleus. We optogenetically stimulated neurons located in the cerebellar cortex Purkinje cells (PCs), the cerebellar nuclei (CN), the red nucleus (RN), the superior colliculus (SC), the spinal trigeminal nucleus (SV), and the reticular formation (RF); in head-fixed awake mice while monitoring the bilateral whisker movement. Here, we find that optogenetic stimulation of the RN, SC, and SV resulted in a predominant midpoint change, whereas optogenetic stimulation of the PCs, CN, and RF resulted in faster whisker movements. In addition, the excitation of PCs, the RN, and SC resulted in symmetric bilateral whisking. In contrast, the excitation of CN, the RF, and SV resulted in initial asymmetric movement, followed by a more dominantly symmetrical bilateral whisking. Our results suggest that several pre-motor nuclei receiving cerebellar output modulate different aspects of whisking, suggesting pattern separation takes place in the brain-wide network downstream of the cerebellum.

neuroscience↗

bioRxiv2025

ATXN2 polyglutamine expansion impairs QKI-dependent alternative splicing and oligodendrocyte maintenance

BackgroundPolyglutamine (polyQ) tract expansion mutations in Ataxin-2 gene (ATXN2) are associated with neurodegenerative diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS), while the therapeutic reduction of ATXN2 confers strong health-/lifespan extension in models of both disorders. Although the involvement of ATXN2 in peripheral lipid metabolism has been elaborated in Atxn2 knock-out mice, its impact on nervous system lipid maintenance and a potential influence on oligodendrocytes remains unexplored. MethodsWe examine the nervous tissue of an authentic ATXN2 polyQ expansion mouse model in terms of (i) gross morphology of the brain and differential glial affection via immunohistochemical analyses, (ii) spinocerebellar proteome profile via label-free mass spectroscopy and (iii) alternative splicing patterns of oligodendroglial transcripts via quantitative RT-PCR. Finally, electrophysiological recording of sensory response in cerebellar Purkinje cells was performed as a phenotypic measure of demyelination. ResultsWe demonstrate a massive impairment in myelin maintenance due to ATXN2 polyQ expansion, affecting key oligodendroglial proteins accompanied by their splicing anomalies much earlier than disease manifestation. Oligodendroglial ATXN2 aggregates were documented for the first time in cerebellum, which sequestrated the RNA splicing factor Quaking (QKI). As an outcome of demyelination, our SCA2 model showed a significant delay in response to sensory stimuli. ConclusionsOverall, we provide pioneer evidence of oligodendroglial proteotoxicity leading to myelin maintenance defects in an authentic mouse model of SCA2. Our findings suggest that not only neuronal metabolism, but also that of oligodendroglia depends on ATXN2 and is affected during the disease course. This novel aspect of ATXN2 pathomechanism sheds light on potential outcomes of its therapeutic manipulation, and makes it relevant also for demyelination syndromes next to SCA2 and other polyQ disorders.

neuroscience↗

bioRxiv2022

Host and pathogen drivers of infection-induced changes in social aggregation behavior

Identifying how infection modifies host behaviours that determine social contact networks is important for understanding heterogeneity in infectious disease dynamics. Here, we investigate whether group social behaviour is modified during bacterial infection in Drosophila melanogaster, an established system for behavioural genetics, according to pathogen species, infectious dose, host genetic background and sex. We find that systemic infection with four different bacterial species results in a reduction in the mean pairwise distance within infected flies, and that the extent of this change depends on the infectious dose in a pathogen-specific way. In the presence of infected conspecifics, susceptible flies also tended to aggregate throughout time, but did not show any evidence of avoiding infected flies. We also observed genetic- and sex-based variation in social aggregation, with infected female flies aggregating more closely than infected males. In general, our results confirm that bacterial infection induces changes in fruit fly behaviour across a range of pathogen species, but also highlight that these effects vary between fly genetic backgrounds and can be sex-specific. We discuss possible explanations for sex differences in social aggregation and their consequences for individual variation in pathogen transmission.

animal behavior and cognition↗

bioRxiv2020

Complex spike firing adapts to saliency of inputsand engages readiness to act

The cerebellum is involved in cognition next to motor coordination. During complex tasks, climbing fiber input to the cerebellum can deliver seemingly opposite signals, covering both motor and non-motor functions. To elucidate this ambiguity, we hypothesized that climbing fiber activity represents the saliency of inputs leading to action-readiness. We addressed this hypothesis by recording Purkinje cell activity in lateral cerebellum of awake mice learning go/no-go decisions based on entrained saliency of different sensory stimuli. As training progressed, the timing of climbing fiber signals switched in a coordinated fashion with that of Purkinje cell simple spikes towards the moment of occurrence of the salient stimulus that required action. Trial-by-trial analysis indicated that emerging climbing fiber activity is not linked to individual motor responses or rewards per se, but rather reflects the saliency of a particular sensory stimulus that engages a general readiness to act, bridging the non-motor with the motor functions. In brief O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/314534v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@c319edorg.highwire.dtl.DTLVardef@db527eorg.highwire.dtl.DTLVardef@104e94eorg.highwire.dtl.DTLVardef@17115f2_HPS_FORMAT_FIGEXP M_FIG C_FIG Mice were trained to identify the saliency of different sensory inputs in that they had to learn to ignore a prominent sound cue and respond to a light tactile cue in a Go/No-Go licking task. As the mice learned to discriminate the two inputs and respond to the proper signal, the Purkinje cells in the lateral cerebellum switched their climbing fiber activity (i.e., complex spike activity) towards the moment of occurrence of the salient stimulus that required a response, while concomitantly shifting the phase of their simple spike modulation. Trial-by-trial analysis indicates that the emerging climbing fiber activity is not linked to the occurrence of the motor response or reward per se, but rather reflects the saliency of a particular sensory stimulus engaging a general readiness to act.

neuroscience↗

bioRxiv2020

Cerebellar Purkinje cells can differentially modulate coherence between sensory and motor cortex depending on region and behavior

Coherence among sensory and motor cortices is indicative of binding of critical functions in perception, motor planning, action and sleep. Evidence is emerging that the cerebellum can impose coherence between cortical areas, but how and when it does so is unclear. Here, we studied coherence between primary somatosensory (S1) and motor (M1) cortices during sensory stimulation of the whiskers in the presence and absence of optogenetic stimulation of cerebellar Purkinje cells in awake mice. Purkinje cell activation enhanced and reduced sensory-induced S1-M1 coherence in the theta and gamma bands, respectively. This impact only occurred when Purkinje cell stimulation was given simultaneously with sensory stimulation; a 20 ms delay was sufficient to alleviate its impact, suggesting the existence of a fast, cerebellar sensory pathway to S1 and M1. The suppression of gamma band coherence upon Purkinje cell stimulation was significantly stronger during trials with relatively large whisker movements, whereas the theta band changes did not show this correlation. In line with the anatomical distribution of the simple spike and complex spike responses to whisker stimulation, this suppression also occurred following focal stimulation of medial crus 2, but not of lateral crus 1. Granger causality analyses and computational modeling of the involved networks suggest that Purkinje cells control S1-M1 coherence most prominently via the ventrolateral thalamus and M1. Our results indicate that coherences between sensory and motor cortices in different frequency ranges can be dynamically modulated by cerebellar input, and that the modulation depends on the behavioral context and is site-specific. Significance StatementCoherent activity between sensory and motor areas is essential in sensorimotor integration. We show here that the cerebellum can differentially affect cortical theta and gamma band coherences evoked by whisker stimulation via a fast ascending and predictive pathway. In line with the functional heterogeneity of its modular organization, the impact of the cerebellum is region-specific and tuned to ongoing motor responses. These data highlight site-specific and context-dependent interactions between the cerebellum and the cerebral cortex that can come into play during a plethora of sensorimotor functions.

neuroscience↗

bioRxiv2019

Functional convergence of autonomic and sensorimotor processing in the lateral cerebellum

The cerebellum is involved in control of voluntary and autonomic rhythmic behaviors, yet it is largely unclear to what extent it coordinates these in a concerted action. Here, we studied Purkinje cell activity during unperturbed and perturbed respiration in cerebellar lobules simplex, crus 1 and 2. During unperturbed (eupneic) respiration complex spike and simple spike activity encoded respiratory activity, the timing of which corresponded with ongoing sensorimotor feedback. Instead, upon whisker stimulation mice concomitantly accelerated their simple spike activity and inspiration in a phase-dependent manner. Moreover, the accelerating impact of whisker stimulation on respiration could be mimicked by optogenetic stimulation of Purkinje cells and prevented by cell-specific genetic modification of their AMPA receptors that hampered increases in simple spike firing. Thus, the impact of Purkinje cell activity on respiratory control is context- and phase-dependent, suggesting a coordinating role for the cerebellar hemispheres in aligning autonomic and sensorimotor behaviors.

neuroscience↗

bioRxiv2018

Aperiodic Rhythms of the Inferior Olive

Inferior olivary activity causes both short-term and long-term changes in cerebellar output underlying motor adaptation and motor learning, respectively. Many of its neurons engage in coherent subthreshold oscillations and are extensively coupled via gap junctions. Studies in reduced preparations suggest that these properties promote rhythmic, synchronized output. However, how these properties interact with synaptic inputs controlling inferior olivary output in intact, awake behaving animals is poorly understood. Here we combine electrophysiological recordings in awake mice with a novel and realistic tissue-scale computational model of the inferior olive to study the relative impact of intrinsic and extrinsic mechanisms governing its activity. Our data and model suggest that oscillations are present in the awake state, but that the period of subthreshold oscillations is variable, resulting in semi-periodic activity, which result in the high unpredictability of sensory-triggered complex spikes occurring in windows of opportunity lasting a few tens of milliseconds. To test the resonant properties of complex spike firing we used different temporal patterns of sensory stimulation in awake mice. Resonance was found to be limited to short intervals no more than a few hundred milliseconds, which could be explained by our network model to be a result of synaptic input to the inferior olive. The model also shows how gap junctional coupling stiffens the olivary network response to sensory modulation of complex spike rhythmicity. Interactions between intrinsic properties and extrinsic inputs can explain short-lasting semi- periodic variations of the spiking rhythms of olivary neurons even though their long-term average firing rate is stable, providing a conceptual framework for the creation of both the short-term and long-term changes in cerebellar output.\n\nAUTHOR SUMMARYActivity of the inferior olive, transmitted via climbing fibers to the cerebellum, regulates initiation and amplitude of movements, signals unexpected sensory feedback, and directs cerebellar learning. It is characterized by widespread subthreshold oscillations and synchronization promoted by strong electrotonic coupling. In brain slices, subthreshold oscillations set a temporal framework determining which inputs can be transmitted by inferior olivary neurons and which will not - dependent on the phase of the oscillation. In our study, we tested whether the subthreshold oscillations had any impact on temporal patterning of climbing fiber activity in intact, awake mice. We did so by recording neural activity of the postsynaptic Purkinje cells, in which complex spike firing faithfully represents climbing fiber activity. For short intervals (<300 ms), we found that many Purkinje cells indeed showed spontaneously rhythmic complex spike activity. However, our experiments designed to evoke resonant responses clearly indicated that complex spikes are not predicated on stimulus history. Our realistic network model of the inferior olive explains the experimental findings via continuous phase modulations of the subthreshold oscillations. We conclude that inferior olivary activity is emerging from an aperiodic rhythm, stabilized by electrotonic coupling, and dependent on the behavioral context transmitted via synaptic input.

neuroscience↗

bioRxiv2018

Adaptation of Whisker Movements Requires Cerebellar Potentiation

Cerebellar plasticity underlies motor learning. However, how the cerebellum operates to enable learned changes in motor output is largely unknown. We developed a sensory-driven adaptation protocol for reflexive whisker protraction and recorded Purkinje cell activity from crus 1 and 2 of awake mice. Before training, simple spikes of individual Purkinje cells correlated during reflexive protraction with the whisker position without lead or lag. After training, simple spikes and whisker protractions were both enhanced with the spiking activity now leading the behavioral response. Neuronal and behavior changes did not occur in two cell-specific mouse models with impaired long-term potentiation at parallel fiber to Purkinje cell synapses. Consistent with cerebellar plasticity rules, increased simple spike activity was prominent in cells with low complex spike response probability. Thus, potentiation at parallel fiber to Purkinje cell synapses may contribute to reflex adaptation and enable expression of cerebellar learning through increases in simple spike activity.\n\nImpact statementRomano et al. show that expression of cerebellar whisker learning can be mediated by increases in simple spike activity, depending on LTP induction at parallel fiber to Purkinje cell synapses.

neuroscience↗