Biology subjects

Muller, L.

Publications and source records attributed to Muller, L..

At least 19 recordsLinked to original sources

bioRxiv2026

Targeting poorly differentiated thyroid cancer with bispecific antibodies and CAR T cells from the human anti-TSHR autoantibody repertoire

Background: Poorly differentiated thyroid carcinoma (PDTC) has no effective systemic treatment option once radioactive iodine and tyrosine kinase inhibitors fail. The thyroid-stimulating hormone receptor (TSHR) is highly tissue-restricted and the anti-TSHR autoantibody repertoire of thyroid autoimmunity offers sequence-defined, fully human binders. We asked whether this repertoire can be converted into an off-the-shelf T cell-redirecting therapy for PDTC. Methods: TSHR expression was profiled on a 151-case thyroid cancer tissue microarray (TMA), 50 healthy controls and on fresh tumor material. Eight anti-TSHR clones, four of human autoimmune origin (M22, K1-18, K1-70, 5C9) and four murine (IRI-SAb2, IRI-SAb3, 9D33, 1H7), were reformatted as CD3-engaging bispecific antibodies (bsAbs; anti-TSHR Fab x anti-CD3 scFv) and, for leading clones, as chimeric antigen receptor (CAR) T cells. Activity was compared in vitro, across graded and mixed antigen densities and in a CAL-62-Luc-TSHR xenograft model, using healthy-donor (HD) or thyroid cancer-patient T cells. Results: TSHR was retained on a substantial fraction of PDTC, including metastatic lesions. Both formats mediated potent, antigen-selective killing and the leading bsAbs suppressed xenograft growth in vivo. For CAR T cells, scFv heavy/light-chain orientation was decisive. Anti-TSHR bsAbs cleared mixed cultures far beyond the antigen-positive fraction matching mosunetuzumab and indicating a modality-intrinsic bystander effect. Patient-derived T cells obtained on or after oncological treatment retained full effector function. Conclusions: The anti-TSHR autoantibody repertoire provides a promising source of binders for off-the-shelf bispecific antibodies targeting TSHR-positive thyroid cancer, while CAR T cells offer an autologous alternative.

cancer biology↗

bioRxiv2026

Novel protein networks in motile cilia from human epithelial cells revealed by cryo-ET and proteomics analysis of cilia from PCD patients

In our past study on human cilia from primary ciliary dyskinesia (PCD) patients using cryo-electron tomography and mass spectrometry, defects in the DNAH5 gene were proven to cause the loss of the entire outer dynein arm along with other proteins. This phenomenon was not observed in the unicellular green alga Chlamydomonas. In this study, we examined the loss of ciliary components caused by defects in various genes, based on proteomic and structural analyses of motile cilia from multiple PCD patients. The absence of single outer arm dynein genes causes a loss or significant decrease in other inner and outer arm dyneins. Interestingly, some patients with outer dynein defects show decreased intraflagellar transport (IFT) proteins, suggesting an influence of cargo components or assembly on transport. These phenomena were not observed in Chlamydomonas, suggesting a more complex mechanism of ciliogenesis in humans despite the high similarity in the final 3D architecture of the 9+2 axoneme. Defects in certain central pair proteins unexpectedly reduced components on the doublets as well. Our results demonstrate protein-protein interactions during stages of human motile ciliogenesis that are more complex than those in unicellular organisms.

cell biology↗

bioRxiv2026

A p32 family RNA editing factor acts in mitochondrial ribosome biogenesis

Biogenesis of mitochondrial ribosomes (mitoribosomes) in the unicellular parasite Trypanosoma brucei requires an exceptionally large toolkit of assembly factors, identified in stable precursors of large and small mitoribosomal subunits (mtLSU and mtSSU) by cryoEM. Here, using genetic modifications and proteomic characterization of the immunoprecipitated assemblosome, the earliest characterized mtSSU precursor, we determined that a cap of its distinctive protrusion of hitherto unknown composition consists of a p22 homotrimer. This protein was previously implicated in the uridine-insertion editing of the cytochrome c oxidase subunit II transcript. Our functional analysis confirmed this role but revealed that its ablation also causes a loss of mtSSU and a systemic reduction in mitochondrial translation, phenocopying the depletion of established mitoribosomal assembly factors. Consequently, the oxidative phosphorylation system and mitochondrial function are compromised. The p22 protein belongs to the p32 family. We showed that five of its six trypanosomal members are involved in mtSSU biogenesis. Notably, p32 proteins are associated with mitoribosomes in two other distant eukaryotic lineages. A eukaryote-wide mapping of p32 proteins documented that their presence correlates with the retention of mitochondrial genomes. Together, our findings redefine trypanosomal p22 as a dual-function coordinator of mitochondrial gene expression and reveal that the ancestral role of the p32 family is associated with mitochondrial translation.

molecular biology↗

bioRxiv2026

dia-PASEF Enables Rapid Profiling of the Human Secretome for Deeper Insights into Cellular Dynamics and Inflammatory Mechanisms

Protein secretion is a fundamental mechanism for cellular coordination and signalling, with its dysregulation leading to widespread physiological dysfunction and disease. Immunoassay formats that utilise secondary antibody readouts are the current gold standard for measuring secreted proteins, offering high specificity and sensitivity, but relying on predefined protein panels that constrain the discovery of novel biology. We present a scalable mass spectrometry-based workflow that combines data-independent acquisition with ion mobility and parallel fragmentation to deliver rapid, global profiling of the secretome. Using a translationally relevant human iPSC-derived macrophage model, our approach identified over 1200 proteins in under 15 minutes of acquisition time, delivering exceptional reproducibility across a large sample set. We applied this approach to profile pro-inflammatory phenotypes, confirming robust identification of key cytokines and chemokines whilst revealing non-canonical immune responses absent from both targeted panels and the intracellular proteome. In particular, we identified a unique cholesterol efflux signature, marked by the secretion of APOA1 and PON1, in response to Mycobacterium Tuberculosis, consistent with the metabolic reprogramming that takes place during infection. Furthermore, temporal profiling of macrophage responses to lipopolysaccharide over 24 hours resolved dynamic secretion trajectories that distinguish between acute and chronic inflammatory states. The extended time period facilitated the observation of distinct cytokine-dependent secretion phenotypes, with early secretion of TNF and IL6 initiating downstream signalling cascades that resulted in the delayed secretion of chemokines such as CXCL10 and CCL8. Collectively, these findings establish a robust, scalable platform for global characterisation of secretory networks. Beyond macrophage biology, this workflow offers broad utility for biomarker discovery, mechanistic studies of disease progression and evaluation of new therapeutic interventions, providing a powerful tool for advancing precision medicine.

immunology↗

bioRxiv2025

Refined cellular activity expression signatures provide a targeted framework to quantify phenotypic intra-tumor heterogeneity in single-cell data

Single cell RNA-seq (scRNA-seq) now allows deeper insight into cellular biology at both the individual and population level. Measuring cell-to-cell variations in the population enables quantification of phenotypic heterogeneity in populations in which cell states and identities deviate from healthy transcriptomic profiles. Cellular activities quantifiable using gene set enrichment analyses can provide useful grounds to quantify phenotypic heterogeneity, but the specificity and adequacy of existing molecular signatures for scRNA-seq data is still insufficient. Here we induced 6 activities in vitro, for which we refined existing expression signatures to enhance specificity and detection in scRNA-seq data: epithelial-mesenchymal transition (EMT), DNA repair, responses to interferons and {gamma} (IFN and IFN{gamma}, respectively), glycolysis, oxidative phosphorylation (OxPhos). We report new signatures, with much lower redundancy between IFN and IFN{gamma}, and glycolysis and OxPhos signatures, achieving average AUCs of 0.85 across bootstrapped datasets for each activity. We could use these signatures to quantify phenotypic intra-tumor heterogeneity (ITH) in 20 patient samples and 14 cell lines, observing high correlation with diversity indices in classified healthy cells (p<0.001). Focusing on cancer cells only, we furthermore report higher phenotypic ITH in patients than in cell lines (p<0.001), and in basal tumors (p=0.028).

cancer biology↗

bioRxiv2025

Hypothalamic recurrent inhibition regulates functional states of stress effector neurons.

Stress triggers rapid and reversible shifts in vital physiological functions from homeostatic operation to emergency response. However, the neural mechanisms regulating such functional stress states remain poorly understood. Here we identify a novel recurrent inhibitory circuit governing functional states of key stress regulatory neurons: corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN). Microendoscopic calcium imaging in freely behaving mice revealed synchronized low-activity state at baselines and a reversible high-activity state during mild stress. Ensemble analysis indicated increased dimensionality of network dynamics during high-activity state. Computational modeling of calcium ensemble data, together with independent modeling of single-unit CRHPVN neurons spiking dynamics, converged to show that recurrent inhibition is a key circuit motif for stress-induced functional state transitions. Guided by model predictions, chemogenetic manipulations of PVN-projecting GABAergic neurons (PVN[->]GABA) revealed their roles in constraining CRHPVN neurons to low-activity state at baselines via a prolonged feedback inhibition. Unexpectedly, slow CRHergic excitation was dispensable for driving this prolonged feedback, whereas glutamatergic transmission predominated at CRH[->]PVN[->]GABA excitatory synapses. Incorporating these findings, we refined our computational model to include fast excitation and slow inhibition, yielding new predictions for circuit operation. Together, our results establish recurrent inhibition as a fundamental circuit motif controlling CRHPVN neurons functional states and highlight the value of iterative experiment-model integration in advancing understanding of neural circuits functions.

neuroscience↗

bioRxiv2025

3D vascularized microtumors unveil aberrant ccRCC vasculature and differential sensitivity to targeted treatments

Clear cell renal cell carcinoma (ccRCC) is largely driven by Von Hippel Lindau (VHL) protein deficiency, promoting epithelial-mesenchymal transition, invasion, and hypervascularization, mediated by vascular endothelial growth factor (VEGF) signaling resulting in a structurally abnormal capillary network, which remains insufficiently defined. Previous studies correlating patient outcome with microvascular density yielded diverse results, underscoring the limitations of conventional parameters to fully capture vascular complexity. While VEGF-targeted anti-angiogenic first-line therapies such as sunitinib prolong progression-free survival in metastatic ccRCC, their efficacy is hampered by resistance mechanisms. This study aims to elucidate the three-dimensional architecture of ccRCC-specific vasculature in the tumor microenvironment, and its response to targeted therapies. Analysis of human ccRCC samples identified two distinct vascular structures, markedly differing from tumor capillaries, termed ponds and sheets, which were further characterized in patient-derived xenografts using advanced 3D microscopy on optically cleared samples. Ponds are large, dilated, irregular structures with wide cavity, whereas sheets are thin, elongated, and collapsed structures. To further dissect endothelial network morphogenesis, we developed an innovative in vitro 3D vascularized microtumor model, faithfully recapitulating the aberrant pond architecture. Dynamic live imaging unraveled the temporal relationship between tumor invasion and pond morphogenesis. Additionally, drug sensitivity assays demonstrated that ponds exhibit lower responsiveness to sunitinib compared to tumor capillaries. Altogether, our 3D model not only captures a specific architecture of ccRCC vascular network but also provides mechanistic insight into its development and therapeutic sensitivity. This model offers a promising avenue for personalized treatment assessment and for identification of novel therapeutic strategies. Statement of significanceA co-culture-engineered model integrating tumor spheroid invasion and capillary morphogenesis recapitulates the ccRCC endothelial structures and their response to treatments.

cancer biology↗

bioRxiv2024

Task-specific topographical maps of neural activity in the primate lateral prefrontal cortex

Neurons in the primate lateral prefrontal cortex (LPFC) flexibly adapt their activity to support a wide range of cognitive tasks. Whether and how the topography of LPFC neural activity changes as a function of task is unclear. In the present study, we address this issue by characterizing the functional topography of LPFC neural activity in awake behaving macaques performing three distinct cognitive tasks. We recorded from chronically implanted multi-electrode arrays and show that the topography of LPFC activity is stable within a task, but adaptive across tasks. The topography of neural activity exhibits a spatial scale compatible with prior anatomical tracing work on a!erent LPFC inputs. Our findings show that LPFC maps of neural population activity are stable for a specific task, providing robust neural codes that support task specialization. Moreover, the variability in functional topographies across tasks indicates activity landscapes can adapt, providing flexibility to LPFC neural codes.

neuroscience↗

bioRxiv2024

A TRANSLAMINAR SPACETIME CODE SUPPORTS TOUCH-EVOKED TRAVELING WAVES

Linking sensory-evoked traveling waves to underlying circuit patterns is critical to understanding the neural basis of sensory perception. To form this link, we performed simultaneous electrophysiology and two-photon calcium imaging through transparent NeuroGrids and mapped touch-evoked cortical traveling waves and their underlying microcircuit dynamics. In awake mice, both passive and active whisker touch elicited traveling waves within and across barrels, with a fast early component followed by a variable late wave that lasted hundreds of milliseconds post-stimulus. Strikingly, late-wave dynamics were modulated by stimulus value and correlated with task performance. Mechanistically, the late wave component was i) modulated by motor feedback, ii) complemented by a sparse ensemble pattern across layer 2/3, which a balanced-state network model reconciled via inhibitory stabilization, and iii) aligned to regenerative Layer-5 apical dendritic Ca2+ events. Our results reveal a translaminar spacetime pattern organized by cortical feedback in the sensory cortex that supports touch-evoked traveling waves. GRAPHICAL ABSTRACT AND HIGHLIGHTS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=66 SRC="FIGDIR/small/593381v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@c98840org.highwire.dtl.DTLVardef@1105364org.highwire.dtl.DTLVardef@d2f2c9org.highwire.dtl.DTLVardef@1418744_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIWhisker touch evokes both early- and late-traveling waves in the barrel cortex over 100s of milliseconds C_LIO_LIReward reinforcement modulates wave dynamics C_LIO_LILate wave emergence coincides with network sparsity in L23 and time-locked L5 dendritic Ca2+ spikes C_LIO_LIExperimental and computational results link motor feedback to distinct translaminar spacetime patterns C_LI

neuroscience↗

bioRxiv2024

Toll-like receptor 3 orchestrates a conserved mechanism of heart regeneration

The humans heart responds to tissue damage with persistent fibrotic scarring. Unlike humans, zebrafish can repair cardiac injury and re-grow heart tissue throughout life. Recently, Toll-like receptor 3 (Tlr3) was identified as an important mediator of cardiac regeneration in neonatal mice. However, no functional analysis of tlr3 knock-out mutant zebrafish in respect to cardiac regeneration has yet been performed. We hypothesize that TLR3 signalling plays a central, conserved role in driving cardiac regeneration upon injury. Therefore, we focused on tlr3 mediated cardiac regeneration in zebrafish, ultimately discovering an evolutionary conserved mechanism of heart repair. Using histological, behavioural, and RNA-Sequencing analysis, we uncovered a conserved mechanism of tlr3 mediated cardiac repair after myocardial injury. Upon myocardial cryoinjury subjection, survival is decreased in tlr3-/- fish as compared to wildtype controls. Tlr3-/- zebrafish fail to recruit immune cells to the injured ventricle, resulting in impaired DNA repair and transcriptional reprogramming of cardiomyocytes. Mechanistically, we uncover an evolutionary conserved mechanism of tlr3 activation in fibroblasts promoting monocyte migration towards an injured ventricular area. Our data reveal tlr3 as a novel therapeutic target to promote cardiac regeneration. Every experiment including human participants has been approved by the ethics committee of the Medical University of Innsbruck (Ref. Nr.: 1262/2023). All experiments including the use of laboratory animals have been approved by the federal ministry of education, science, and research of Austria (Ref. Nr.: 2020-0.345.504).

molecular biology↗

bioRxiv2023

CompHEAR: A Customizable and Scalable Web-Enabled Auditory Performance Evaluation Platform for Cochlear Implant Sound Processing Research

ObjectiveCochlear implants (CIs) are auditory prostheses for individuals with severe to profound hearing loss, offering substantial but incomplete restoration of hearing function by stimulating the auditory nerve using electrodes. However, progress in CI performance and innovation has been constrained by the inability to rapidly test multiple sound processing strategies. Current research interfaces provided by major CI manufacturers have limitations in supporting a wide range of auditory experiments due to portability, programming difficulties, and the lack of direct comparison between sound processing algorithms. To address these limitations, we present the CompHEAR research platform, designed specifically for the Cochlear Implant Hackathon, enabling researchers to conduct diverse auditory experiments on a large scale. Study DesignQuasi-experimental SettingVirtual MethodsCompHEAR is an open-source, user-friendly platform which offers flexibility and ease of customization, allowing researchers to set up a broad set of auditory experiments. CompHEAR employs a vocoder to simulate novel sound coding strategies for CIs. It facilitates even distribution of listening tasks among participants and delivers real-time metrics for evaluation. The software architecture underlies the platforms flexibility in experimental design and its wide range of applications in sound processing research. ResultsPerformance testing of the CompHEAR platform ensured that it could support at least 10,000 concurrent users. The CompHEAR platform was successfully implemented during the COVID-19 pandemic and enabled global collaboration for the CI Hackathon (www.cihackathon.com). ConclusionThe CompHEAR platform is a useful research tool that permits comparing diverse signal processing strategies across a variety of auditory tasks with crowdsourced judging. Its versatility, scalability, and ease of use can enable further research with the goal of promoting advancements in cochlear implant performance and improved patient outcomes.

neuroscience↗

bioRxiv2023

Cortical tracking of postural sways during standing balance.

Maintaining an upright stance requires the integration of sensory inputs from the visual, vestibular and somatosensory-proprioceptive systems by the central nervous system to develop a corrective postural strategy. However, it is unclear whether and how the cerebral cortex monitors and controls postural sways. Here, we asked whether postural sways are encoded in ongoing cortical oscillations, giving rise to a form of corticokinematic coherence (CKC) in the context of standing balance. Center-of-pressure (CoP) fluctuations and electroencephalographic cortical activity were recorded as young healthy participants performed balance tasks during which sensory information was manipulated, by either removal or alteration. We found that postural sways are represented in ongoing cortical activity during challenging balance conditions, in the form of CKC at 1-6 Hz. Time delays between cortical activity and CoP features indicated that both afferent and efferent pathways contribute to CKC, wherein the brain would monitor the CoP velocity and control its position. Importantly, CKC was behaviorally relevant, as it predicted the increase in instability brought by alteration of sensory information. Our results suggest that human sensorimotor cortical areas take part in the closed-loop control of standing balance in challenging conditions. Importantly, CKC could serve as a neurophysiological marker of cortical involvement in maintaining balance.

neuroscience↗

bioRxiv2023

Controlling focality and intensity of non-invasive deep brain stimulation using multipolar temporal interference in non-human primates and rodents

Temporal interference (TI) is a method of non-invasive brain stimulation using transcutaneous electrodes that allows the targeting and modulation of deeper brain structures, not normally associated with non-invasive simulation, while avoiding unwanted stimulation of shallower cortical structures. The properties of TI have been previously demonstrated, however, the problem of decoupling stimulation focality from stimulation intensity has not been addressed. In this paper, we provide a possible novel solution, multipolar TI (mTI), which allows increased independent control over both the size of the stimulated region and the stimulation intensity. The mTI method uses multiple carrier frequencies to create multiple overlapping amplitude-modulated envelopes, rather than using one envelope as in standard TI. The study presents an explanation of the concept of mTI along with experimental data gathered from Rhesus macaques and mice. We improved the focality at depth in anesthetized mice and monkeys, and using the new focality in awake monkeys, evoked targeted activity at depth in the superior colliculus. The mTI method could be an interesting and potentially useful new tool alongside other forms of non-invasive brain stimulation. Teaser: Multipolar Temporal Interference Stimulation can produce a more focal brain stimulation at depth compared to Temporal Interference.

neuroscience↗

bioRxiv2023

The hippocampus of the common marmoset is a GPS, but G is for gaze

The mammalian hippocampus has been compared to a Global Positioning System (GPS) that enables spatial navigation. This notion has been primarily drawn from studies conducted in nocturnal mammals, such as rats; that lack many adaptations to daylight vision compared to diurnal primates. Here we demonstrate that during foraging in a 3D maze, the common marmoset, a new world diurnal primate with foveal, stereo-color vision, predominantly uses rapid head-gaze shifts to visually explore their surroundings while remaining stationary, and then minimizes head movements to navigate towards goals. On the other hand, rats, mainly move their head at low velocities while locomoting to explore the environment using their whiskers. These differences in exploration-navigation strategies reflect the species sensory adaptations to different ecological niches. In the marmoset hippocampus CA3/CA1 regions putative pyramidal neurons show selectivity for 3D view, head direction, and less for place, but mainly mixed selectivity for combinations of these variables. Despite weak place selectivity, the spatial position of the animal in the maze can be decoded from the activity of small ensembles of mixed selective neurons. Inhibitory interneurons are tuned to 3D angular head velocity and translation speed, with most cells showing mixed selectivity for both variables. Finally, marmosets lack the rhythmic theta oscillations of local field potentials seen during locomotion in rats. Instead, they show resetting of theta oscillations triggered by head-gaze shifts that co-occurred with the activation of inhibitory interneurons, followed by various modulations in the activity of pyramidal cells. Our results show that the marmoset visual exploration/navigation strategies and the hippocampal neuronal specializations supporting them diverge from those observed in rats, reflecting the far-sensing capabilities of the marmoset visual system adapted to diurnal lifestyle.

neuroscience↗

bioRxiv2023

Spatial transcriptomics reveal pitfalls and opportunities for the detection of rare high-plasticity breast cancer subtypes

Breast cancer is one of the most prominent types of cancers, in which therapeutic resistance is still a major clinical hurdle. Specific subtypes like Claudin-low (CL) and metaplastic breast cancers (MpBC) have been associated with high non-genetic plasticity, which can facilitate resistance. The overlaps and differences between these orthogonal subtypes, respectively identified by molecular and histopathological analyses, are however still insufficiently characterised. Adequate methods to identify high-plasticity tumours to better anticipate resistance are furthermore still lacking. Here we analysed 11 triple negative breast tumours, including 3 CL and 4 MpBC samples, via high-resolution spatial transcriptomics. We combined pathological annotations and deconvolution approaches to precisely identify tumour spots, on which we performed signature enrichment, differential expression and copy-number analyses. We used the TCGA and CCLE public databases for external validation of expression markers. By levying spatial transcriptomics to focus analyses only to tumour cells in MpBC samples, and therefore bypassing the negative impact of stromal contamination, we could identify specific markers that are not expressed in other subtypes nor stromal cells. Three markers (BMPER, POPDC3 and SH3RF3) could furthermore be validated in external expression databases encompassing bulk tumour material and stroma-free cell lines. We find that existing bulk expression signatures of high-plasticity breast cancers are relevant in mesenchymal transdifferentiated compartments but can be hindered by stromal cell prevalence in tumour samples, negatively impacting their clinical applicability. Spatial transcriptomics analyses can however help identify more specific expression markers, and could thus enhance diagnosis and clinical care of rare high-plasticity breast cancers.

cancer biology↗

bioRxiv2022

Spike-phase coupling patterns reveal laminar identity in primate cortex

The cortical column is one of the fundamental computational circuits in the brain. In order to understand the role neurons in different layers of this circuit play in cortical function it is necessary to identify the boundaries that separate the laminar compartments. While histological approaches can reveal ground truth they are not a practical means of identifying cortical layers in vivo. The gold standard for identifying laminar compartments in electrophysiological recordings is current-source density (CSD) analysis. However, laminar CSD analysis requires averaging across reliably evoked responses that target the input layer in cortex, which may be difficult to generate in less well studied cortical regions. Further the analysis can be susceptible to noise on individual channels resulting in errors in assigning laminar boundaries. Here, we have analyzed linear array recordings in multiple cortical areas in both the common marmoset and the rhesus macaque. We describe a pattern of laminar spike-field phase relationships that reliably identifies the transition between input and deep layers in cortical recordings from multiple cortical areas in two different non-human primate species. This measure corresponds well to estimates of the location of the input layer using CSDs, but does not require averaging or specific evoked activity. Laminar identity can be estimated rapidly with as little as a minute of ongoing data and is invariant to many experimental parameters. This method may serve to validate CSD measurements that might otherwise be unreliable or to estimate laminar boundaries when other methods are not practical.

neuroscience↗

bioRxiv2022

Distinct contact guidance mechanisms in single endothelial cells and in monolayers

In many tissues, cell shape and orientation are controlled by a combination of internal and external biophysical cues. Anisotropic substrate topography is a ubiquitous cue that leads to cellular elongation and alignment, a process termed contact guidance, whose underlying mechanisms remain incompletely understood. Additionally, whether contact guidance responses are similar in single cells and in cellular monolayers is unknown. Here, we address these questions in vascular endothelial cells (ECs) that in vivo form a monolayer that lines blood vessels. Culturing single ECs on microgrooved substrates that constitute an idealized mimic of anisotropic basement membrane topography elicits a strong, groove depth-dependent contact guidance response. Interestingly, this response is greatly attenuated in confluent monolayers. While contact guidance in single cells is principally driven by persistence bias of cell protrusions in the direction of the grooves and is surprisingly insensitive to actin stress fiber disruption, cell shape and alignment in dense EC monolayers are driven by the organization of the basement membrane secreted by the cells, which leads to a loss of interaction with the microgrooves. The findings of distinct contact guidance mechanisms in single ECs and in EC monolayers promise to inform strategies aimed at designing topographically patterned endovascular devices.

cell biology↗

bioRxiv2022

State-dependent activity dynamics of hypothalamic stress effector neurons

The stress response necessitates an immediate boost in vital physiological functions from their homeostatic operation to elevated emergency response. However, neural mechanisms underlying this state-dependent change remain largely unknown. Using a combination of in vivo and ex vivo electrophysiology with computational modeling, we report that corticotropin releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN), the effector neurons of hormonal stress response, rapidly transition between distinct activity states through recurrent inhibition. Specifically, in vivo optrode recording shows that under non-stress conditions, CRHPVN neurons often fire with rhythmic brief bursts (RB), which, somewhat counterintuitively, constrains firing rate due to long ([~]2 s) inter-burst intervals. Stressful stimuli rapidly switch RB to continuous single spiking (SS), permitting a large increase in firing rate. A spiking network model shows that recurrent inhibition can control this activity-state switch, and more broadly the gain of spiking responses to excitatory inputs. In biological CRHPVN neurons ex vivo, the injection of whole-cell currents derived from our computational model recreates the in vivo-like switch between RB and SS, providing a direct evidence that physiologically relevant network inputs enable state-dependent computation in single neurons. Together, we present a novel mechanism for state-dependent activity dynamics in CRHPVN neurons.

neuroscience↗