Biology subjects

Bauer, L.

Publications and source records attributed to Bauer, L..

At least 19 recordsLinked to original sources

bioRxiv2025

Non-polio enteroviruses compromise the electrophysiology of a human iPSC-derived neural network

The non-polio enteroviruses enterovirus-D68 (EV-D68) and enterovirus-A71 (EV-A71) are highly prevalent and considered pathogens of increasing health concern. While most enterovirus infections are mild and self-limiting, severe complications ranging from meningitis, encephalitis, to acute flaccid paralysis can occur, especially in children and immunocompromised patients. Despite the global burden of neurological complications caused by EV-D68 and EV-A71, the underlying neuropathogenesis remains poorly understood. In particular, the impact of the infection on neural function has not been clearly elucidated. Here, we compare the replication kinetics, cellular tropism, and electrophysiological effects of EV-D68 and EV-A71 infection in a physiologically relevant human pluripotent stem cell-derived neural co-culture model, consisting of excitatory neurons and astrocytes. Inoculation with contemporary circulating EV-D68 strains and an EV-A71 strain resulted in decreased neural activity in the co-cultures, with EV-D68 A2/2018 inducing the most rapid and robust negative effect on neural co-cultures, followed by EV-D68 B3/2019. EV-D68 strains preferentially infected neurons, whereas EV-A71 infection was detected in both cell types to the same extent. Despite the lack of viral release of infectious virus particles of EV-D68 B3/2019 in the supernatant, the infection could spread in the cultures and reduce neurotransmission. Higher viral load and broader tropism of EV-A71 did not result in enhanced impairment of neural function. Our results demonstrate that neurotropic non-polio enteroviruses lead to disruption of spontaneous neural activity in a virus-specific manner, which does not correlate with their replication efficiency.

microbiology↗

bioRxiv2025

Influenza A Virus Infection Impairs Neuronal Activity in Human iPSC-Derived NGN2 Neural Co-Cultures

Influenza A virus (IAV) infection is associated with a wide variety of neurological complications, of which mild complications like impaired cognitive functioning are most prominent. Even though several studies have shown that many influenza viruses can enter the CNS, the neuropathogenesis of seasonal (H3N2 and H1N1) and pandemic (pH1N1 2009) IAV infections is poorly understood. Therefore, we aimed to investigate the cellular tropism, replication efficiency and associated functional consequences using a human stem cell-derived neural co-culture model of neurons and astrocytes. All viruses were able to infect neurons in the co-culture model, although this infection did not result in efficient replication and release of progeny virus. In addition, infection did not result in visible cell death or apoptosis. However, functional analyses revealed that IAV inoculation resulted in a reduction of spontaneous neural activity and a partial reduction of neural excitability. This study shows that seasonal and pandemic IAVs can disrupt neural homeostasis, without efficient virus replication or the induction of cell death. However, these functional changes in neural activity can contribute to cognitive problems during IAV infections in the acute and potentially post-acute phase of the infection.

microbiology↗

bioRxiv2025

Establishment of menthol bleaching protocols for six stony coral species

The mutualistic symbiosis between stony corals and unicellular algae of the family Symbiodiniaceae forms the base of coral reef ecosystems. However, anthropogenic stressors, such as rising seawater temperatures, cause a breakdown of the coral-algal symbiosis, so-called coral bleaching, which leads to mass mortalities and a rapid loss of coral reefs. To functionally disassemble the coral-algal symbiosis, corals have been artificially rendered aposymbiotic using temperature stress, DCMU, or menthol. As menthol has proven to be an efficient and gentle bleaching agent, we tested four menthol treatments with six commonly investigated stony coral species. The overarching aim was to establish a broadly efficient bleaching protocol as a guide for future investigations. Menthol-induced bleaching was traced with chlorophyll fluorescence and tissue color analyses over time and confirmed as final symbiont cell density two weeks after the last day of menthol treatment. Here we found that the coral species varied greatly in their menthol bleaching tolerance, underlining the importance of establishing bespoke bleaching approaches. Acropora muricata and Stylophora pistillata were efficiently bleached within two days of menthol exposure with symbiont cell reductions of 94 % to 98 %. For Galaxea fascicularis, Montipora digitata and Porites cylindrica, six days of menthol exposure proved most successful in reducing symbiont density by 92 to 97 %. While these coral species suffered no mortality, fragments of Pocillopora verrucosa died or suffered severe necrosis in most of the protocols, making the tested menthol treatments unsuitable for this species. We demonstrate that repeated menthol treatment at low concentrations renders most coral species aposymbiotic within few days without visual or physiological damage. Our study, therefore, provides a guideline for efficient and customized application of menthol bleaching treatments for future coral symbiosis research.

systems biology↗

bioRxiv2025

Enterovirus D68 infection of human inducible pluripotent stem cell-derived skeletal muscles resulted in structural destruction, loss of muscle function and hampered muscle regeneration

Enterovirus D68 (EV-D68) is an emerging respiratory virus that commonly causes mild to severe respiratory diseases. EV-D68 infection is also associated with extra-respiratory complications, especially acute flaccid myelitis. However, how the virus invades the central nervous system (CNS) and infects motor neurons is not fully understood. One possible neuroinvasive route is through infection of skeletal muscles, which allows the virus to infect motor neurons via the neuromuscular junction. However, we hypothesise that direct EV-D68 infection of human skeletal muscles can impair muscle function and thus contribute to the development of EV-D68-associated muscle weakness. Here, we inoculated human induced pluripotent stem cell-derived skeletal muscle myotubes grown in 2D with different EV-D68 isolates, which resulted in a productive infection and cell death. We showed, through neuraminidase treatment, that sialic acids facilitate infection of these cells. EV-D68 infection of 3D tissue engineered skeletal muscles led to tissue damage, reduction of contractile force and depletion of muscle and satellite cells. Altogether, we showed that human skeletal muscle can act as an extra-respiratory replication site and infection of skeletal muscles may contribute to EV-D68-associated muscle weakness. Author summaryAfter causing a global outbreak in 2014, enterovirus D68 (EV-D68) - a respiratory virus - has been associated with polio-like paralysis. How the virus spreads from the respiratory system to the central nervous system is poorly understood. One of the possible routes for this spread is by infecting skeletal muscles before spreading to motor neurons. However, it is not known whether the virus can infect human skeletal muscles and whether EV-D68 infection of skeletal muscles can also lead to paralysis. Here, we used 2D and 3D human skeletal muscle models to investigate EV-D68 infection of human skeletal muscles. We found that EV-D68 can replicate in these 2D and 3D models and the infection results in destruction of muscle fibres and loss of muscle function. We also found that the infection results in loss of satellite cells, which are important for muscle regeneration, suggesting that EV-D68 infection hampers skeletal muscle regeneration. Our study provides new insights into the potential role of human skeletal muscles in EV-D68-associated paralysis.

microbiology↗

bioRxiv2025

Sialic acid-containing glycolipids extend the receptor repertoire of Enterovirus-D68

Enterovirus D68 (EV-D68) emerged as a pathogen of increasing health concern globally, particularly due to its association with outbreaks of severe respiratory diseases and acute flaccid myelitis (AFM) in children. Knowledge regarding the tissue tropism and pathogenesis of EV-D68 within the respiratory tract and central nervous system remains limited, primarily due to an incomplete understanding of the host factors that facilitate EV-D68 entry into host cells. Several cellular receptors involved in EV-D68 infections have been identified, including ICAM-5, sialylated glycoproteins, and heparan sulfate (HS). Here, we investigate the receptor requirement of a panel of EV-D68 strains covering all clades focusing on HS and sialosides utilizing glycan arrays. We found that all EV-D68 strains binding to HS harbour a cell culture adaptative substitution in the structural protein VP1 at position 271 which changes the amino acid into a positive charged one. Glycan array analyses revealed that EV-D68 strains either prefer 2,6-linked sialic acids presented on N-glycans, 2,8 linked sialic acids on gangliosides, or both. Inhibition of glycolipid biosynthesis or multivalent glycolipid mimics confirmed that ganglioside structures serve as entry receptors for certain EV-D68 strains. Lastly, we examined whether EV-D68 strains that bind to HS or glycolipids require different uncoating mechanisms. Bafilomycin A1 minimally affected cell entry of HS-binding EV-D68 strains B2/039 and B2/947 and the ganglioside preferring B1/2013 other viruses were strongly inhibited. Together, we identified that EV-D68 strains can use disialoglycolipids as novel receptors and that different EV-D68 strains show a promiscuous sialic acid binding repertoire.

microbiology↗

bioRxiv2024

RGB color indices as proxy for symbiont cell density and chlorophyll content during coral bleaching

Coral bleaching, the breakdown of the symbiosis between the coral host and endosymbiotic microalgae, is the main cause of widespread coral reef degradation. Current methods for assessing coral health based on visual appearance, such as the use of color reference cards, are limited by subjective human color perception and low resolution. Digital photography with RGB (Red, Green, Blue) color channel analyses offers a fast, non-invasive, and standardized alternative to estimate physiological parameters. However, the link between coral color and physiological parameters during bleaching may vary depending on the type of stressor. While such approaches are extensively used in plant studies, their application in estimating Symbiodiniaceae cell density and chlorophyll content in corals requires further attention. In this study, we analyzed the correlation between Symbiodiniaceae cell density and chlorophyll content across three coral species (Acropora muricata, Pocillopora verrucosa, and Stylophora pistillata) with 19 color indices derived from the RGB channels currently established as predictors of chlorophyll content in plants. Corals were exposed to three bleaching conditions (acute short-term and chronic long-term heat stress and menthol bleaching) to identify the best color indices for assessing coral health through image analysis. We found that the Red index had the strongest linear correlation with symbiont cell density and chlorophyll content across species (R2 up to 0.97), so that relative changes in this color index can be directly interpreted as corresponding changes in tissue parameters. To train a model that predicts symbiont densities of a distinct sample set using the Red index, we found 10 to 12 samples to be sufficient to achieve an accuracy of > 95 % of the models trained on the full datasets. This research contributes to improved image analysis as a reliable and non-invasive tool for monitoring, by providing guidelines for a systematic use of RGB data to interpret coral health.

ecology↗

bioRxiv2024

A 2022 avian H5N1 influenza A virus from clade 2.3.4.4b attaches to and replicates better in human respiratory epithelium than a 2005 H5N1 virus from clade 2.3.2.1

BackgroundHighly pathogenic avian influenza (HPAI) H5 viruses of the A/Goose/Guangdong/1/1996 (GsGd) lineage pose significant global risks to wildlife, domestic animals, and humans. Recent cross-species transmission events to mammals, including humans, highlight this risk. Critical determinants for cross-species and intra-species transmission include the ability to attach to and replicate in respiratory epithelial cells. Although these factors have been studied for HPAI H5N1 viruses in the past, limited studies are available for currently circulating strains. MethodsWe compared level of adaptation to human respiratory tract of a HPAI H5N1 clade 2.3.4.4b (H5N12022) virus with those of well characterized HPAI H5N1 clade 2.1.3.2 (H5N12005) and seasonal H3N22003 viruses by three methods. First, we compared pattern of virus attachment by virus histochemistry. Second, we compared efficiency of infection and replication, as well as innate immune responses in human respiratory epithelium in vitro. Lastly, we compared polymerase complex activity in a minigenome assay. FindingsThe H5N12022 virus attached more abundantly to and replicated more efficiently in cells of the human respiratory tract compared to H5N12005 and H3N2 viruses. This increased replication was not associated with an increased polymerase activity of H5N12022 virus compared to H3N22003 virus. The efficient replication of H5N12022 virus infection induced a robust innate immune response almost comparable to H3N22003. InterpretationThe pattern of virus attachment and replication efficiency of a HPAI H5N12022 virus resembled that of H3N22003 virus more closely than a HPAI H5N12005. This could contribute to an increased risk for both human infection and virus adaptations to humans. FundingThe Netherlands Organization for Health Research and Development Research in contextO_ST_ABSEvidence before this studyC_ST_ABSHighly pathogenic avian influenza (HPAI) H5 viruses of the A/Goose/Guangdong/1/1996 (GsGd) lineage (clade 2.3.4.4b) have the ability to spread to a wide range of domesticated and wild mammalian species, including humans. Cross species transmission and transmission among humans requires-- among other factors--efficient infection of epithelial cells in the respiratory epithelium of the upper respiratory tract. Added value of this studyIn our study we show that a recent clade 2.3.4.4b HPAI H5N1 virus attached to and replicated more efficiently in respiratory epithelium than a clade 2.1.3.2 H5N1 virus that circulated in 2005. Implications of all the available dataThese data suggest that there might be an increased risk of human infections with the currently circulating 2.3.4.4b HPAI H5N1 viruses, which might facilitate opportunities for human adaptation.

microbiology↗

bioRxiv2024

Neuroinvasive and neurovirulent potential of SARS-CoV-2 in the acute and post-acute phase of intranasally inoculated ferrets

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) can cause systemic disease, including neurological complications, even after mild respiratory disease. Previous studies have shown that SARS-CoV-2 infection can induce neurovirulence through microglial activation in the brains of patients and experimentally inoculated animals, which are models representative for moderate to severe respiratory disease. Here, we aimed to investigate the neuroinvasive and neurovirulent potential of SARS-CoV-2 in intranasally inoculated ferrets, a model for subclinical to mild respiratory disease. The presence of viral RNA, histological lesions, virus-infected cells, and the number and surface area of microglia and astrocytes were investigated. Viral RNA was detected in various respiratory tissue samples by qPCR at 7 days post inoculation (dpi). Virus antigen was detected in the nasal turbinates of ferrets sacrificed at 7 dpi and was associated with inflammation. Viral RNA was detected in the brains of ferrets sacrificed 7 dpi, but in situ hybridization nor immunohistochemistry did not verify evidence of infection. Histopathological analysis of the brains showed no evidence for an influx of inflammatory cells. Despite this, we observed an increased number of Alzheimer type II astrocytes in the hindbrains of SARS-CoV-2 inoculated ferrets. Additionally, we detected an increased microglial activation in the olfactory bulb and hippocampus, and a decrease in the astrocytic activation status in the white matter and hippocampus of SARS-CoV-2 inoculated ferrets. In conclusion, although showed that SARS-CoV-2 has limited neuroinvasive potential in this model for subclinical to mild respiratory disease, there is evidence for neurovirulent potential. This study highlights the value of this ferret model to study the neuropathogenecity of SARS-CoV-2 and reveals that a mild SARS-CoV-2 infection can affect both microglia and astrocytes in different parts of the brain.

microbiology↗

bioRxiv2023

Target-based discovery of a broad spectrum flukicide

Diseases caused by parasitic flatworms impart a considerable healthcare burden worldwide. Many of these diseases - for example, the parasitic blood fluke infection, schistosomiasis - are treated with the drug praziquantel (PZQ). However, PZQ is ineffective against disease caused by liver flukes from the genus Fasciola. This is due to a single amino acid change within the target of PZQ, a transient receptor potential ion channel (TRPMPZQ), in Fasciola species. Here we identify benzamidoquinazolinone analogs that are active against Fasciola TRPMPZQ. Structure-activity studies define an optimized ligand (BZQ) that caused protracted paralysis and damage to the protective tegument of these liver flukes. BZQ also retained activity against Schistosoma mansoni comparable to PZQ and was active against TRPMPZQ orthologs in all profiled species of parasitic fluke. This broad spectrum activity was manifest as BZQ adopts a pose within the binding pocket of TRPMPZQ dependent on a ubiquitously conserved residue. BZQ therefore acts as a universal activator of trematode TRPMPZQ and a first-in-class, broad spectrum flukicide.

microbiology↗

bioRxiv2023

Dissecting the neurotropism and neurovirulence of MPXV using human stem cell-based models

Mpox is a zoonotic illness of international concern that can lead to severe disease including neurological sequelae. However, the neurotropism of monkeypox virus (MPXV) and the mechanisms regulating cell-intrinsic antiviral immunity within the central nervous system (CNS) remain poorly understood. Here, we investigated the neurotropism of MPXV using astrocytes, cortical neurons, and microglia derived from human pluripotent stem cells (hPSCs) and ex vivo human brain tissue to demonstrate that MPXV infects and replicates more efficiently in astrocytes and microglia compared to cortical neurons. Upon MPXV exposure, glial cells, in contrast to cortical neurons, inhibit type I IFN antiviral programs potentially conferring differential susceptibility to MPXV. Furthermore, we demonstrate that treatment using either IFN-beta or tecovirimat inhibits MPXV infection. Together, our results suggest that MPXV has a broad tropism within the CNS and that differential type I IFN signaling underpins cell type-specific susceptibility to MPXV infection.

microbiology↗

bioRxiv2023

Predicting alcohol-related memory problems in older adults: A machine learning study with multi-domain features

Memory problems are common among older adults with a history of alcohol use disorder (AUD). Employing a machine learning framework, the current study investigates the use of multi-domain features to classify individuals with and without alcohol-induced memory problems. A group of 94 individuals (ages 50-81 years) with alcohol-induced memory problems (Memory group) were compared with a matched Control group who did not have memory problems. The Random Forests model identified specific features from each domain that contributed to the classification of Memory vs. Control group (AUC=88.29%). Specifically, individuals from the Memory group manifested a predominant pattern of hyperconnectivity across the default mode network regions except some connections involving anterior cingulate cortex which were predominantly hypoconnected. Other significant contributing features were (i) polygenic risk scores for AUD, (ii) alcohol consumption and related health consequences during the past 5 years, such as health problems, past negative experiences, withdrawal symptoms, and the largest number of drinks in a day during the past 12 months, and (iii) elevated neuroticism and increased harm avoidance, and fewer positive "uplift" life events. At the neural systems level, hyperconnectivity across the default mode network regions, including the connections across the hippocampal hub regions, in individuals with memory problems may indicate dysregulation in neural information processing. Overall, the study outlines the importance of utilizing multidomain features, consisting of resting-state brain connectivity collected [~]18 years ago, together with personality, life experiences, polygenic risk, and alcohol consumption and related consequences, to predict alcohol-related memory problems that arise in later life.

neuroscience↗

bioRxiv2022

The pro-inflammatory response to influenza A virus infection is fueled by endothelial cells

Morbidity and mortality from influenza are associated with high levels of systemic inflammation. Endothelial cells have been shown to play a key role in this systemic inflammatory response during severe influenza A virus (IAV) infections, despite the fact that these are rarely infected in humans. However, how endothelial cells contribute to these systemic inflammatory responses is unclear. To investigate this, we developed a transwell-system in which airway organoid-derived differentiated human lung epithelial cells at the apical side were co-cultured with primary human lung microvascular endothelial cells (LMEC) at the basolateral side. We compared the susceptibility of endothelial cells to pandemic H1N1 virus isolated in 2009 and seasonal H1N1 and H3N2 virus isolated in 2019, and assessed the associated immune responses. Despite the detection of IAV nucleoprotein in LMEC monocultures, there was no evidence for productive infection. In epithelial-endothelial co-cultures, abundant IAV infection of epithelial cells resulted in the breakdown of the epithelial barrier, but infection of LMECs was rarely detected. Furthermore, we observed a significantly higher secretion of pro-inflammatory cytokines in LMECs when co-cultured with IAV-infected epithelial cells, compared to LMEC monocultures exposed to IAV. Taken together, our data show that endothelial cells are abortively infected by IAV, but can fuel the inflammatory response. As endothelial cells are a prominent cell type in the lung, it is possible that they play an important role in the systemic inflammatory response during IAV infections.

microbiology↗

bioRxiv2022

Differences in neuroinflammation in the olfactory bulb between D614G, Delta and Omicron BA.1 SARS-CoV-2 variants in the hamster model

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with various neurological complications. SARS-CoV-2 infection induces neuroinflammation in the central nervous system (CNS), whereat the olfactory bulb seems to be involved most frequently. Here we show differences in the neuroinvasiveness and neurovirulence among SARS-CoV-2 variants in the hamster model five days post inoculation. Replication in the olfactory mucosa was observed in all hamsters, but most prominent in D614 inoculated hamsters. We observed neuroinvasion into the CNS via the olfactory nerve in D614G-, but not Delta (B.1.617.2)- or Omicron BA.1 (B.1.1.529) inoculated hamsters. Neuroinvasion was associated with neuroinflammation in the olfactory bulb of hamsters inoculated with D614G but hardly in Delta or Omicron BA.1. Altogether, this indicates that there are differences in the neuroinvasive and neurovirulent potential among SARS-CoV-2 variants in the acute phase of the infection in the hamster model.

microbiology↗

bioRxiv2021

Fluoxetine targets an allosteric site in the enterovirus 2C AAA+ ATPase and stabilizes the hexameric complex

The enterovirus genus encompasses many clinically important human pathogens such as poliovirus, coxsackieviruses, echoviruses, numbered enteroviruses and rhinoviruses. These viruses are the etiological agents of several human diseases, including hand-foot-and-mouth disease, neonatal sepsis, encephalitis, meningitis, paralysis and respiratory infections. There is an unmet need for antivirals to treat these diseases. The non-structural protein 2C is a AAA+ helicase and plays a key role in viral replication. As such, it is an attractive target for antiviral drug development. Several repurposing screens with FDA-approved drugs have identified 2C-targeting compounds such as fluoxetine and dibucaine, but the molecular basis of 2C inhibition has remained enigmatic. Here we present the 1.5 [A] resolution crystal structure of the soluble fragment of coxsackievirus B3 2C protein in complex with (S)-fluoxetine (SFX), which reveals a conserved, hydrophobic drug-binding pocket which is distal to the ATP binding site. To decipher the molecular mechanism of inhibition by fluoxetine and other 2C-targeting compounds, we engineered a soluble, hexameric and ATPase competent 2C protein. Using this system, we show that SFX, dibucaine, HBB and guanidine hydrochloride inhibit 2C ATPase activity in a dose-dependent manner. Moreover, using cryo-EM analysis, we demonstrate that SFX and dibucaine lock 2C in a defined hexameric state, rationalizing their mode of inhibition and allowing us to generate the first reconstruction of the oligomeric complex. Taken together, these results provide important structural and mechanistic insights into 2C inhibition and provide a robust engineering strategy which can be used for structural, functional and drug-screening analysis of 2C proteins from current or future enteroviruses.

microbiology↗

bioRxiv2021

Replication kinetic, cell tropism and associated immune responses in SARS-CoV-2 and H5N1 virus infected human iPSC derived neural models

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is associated with a wide variety of neurological complications. Even though SARS-CoV-2 is rarely detected in the central nervous system (CNS) or cerebrospinal fluid, evidence is accumulating that SARS-CoV-2 might enter the CNS via the olfactory nerve. However, what happens after SARS-CoV-2 enters the CNS is poorly understood. Therefore, we investigated the replication kinetics, cell tropism, and associated immune responses of SARS-CoV-2 infection in different types of neural cultures derived from human induced pluripotent stem cells (hiPSCs). SARS-CoV-2 was compared to the neurotropic and highly pathogenic H5N1 influenza A virus. SARS-CoV-2 infected a minority of individual mature neurons, without subsequent virus replication and spread, despite ACE2, TMPRSS2 and NPR1 expression in all cultures. However, this sparse infection did result in the production of type-III-interferons and IL-8. In contrast, H5N1 virus replicated and spread very efficiently in all cell types in all cultures. Taken together, our findings support the hypothesis that neurological complications might result from local immune responses triggered by virus invasion, rather than abundant SARS-CoV-2 replication in the CNS.

microbiology↗

bioRxiv2020

Deep learning and automated Cell Painting reveal Parkinson's disease-specific signatures in primary patient fibroblasts

Drug discovery for diseases such as Parkinsons disease are impeded by the lack of screenable cellular phenotypes. We present an unbiased phenotypic profiling platform that combines automated cell culture, high-content imaging, Cell Painting, and deep learning. We applied this platform to primary fibroblasts from 91 Parkinsons disease patients and matched healthy controls, creating the largest publicly available Cell Painting image dataset to date at 48 terabytes. We use fixed weights from a convolutional deep neural network trained on ImageNet to generate deep embeddings from each image and train machine learning models to detect morphological disease phenotypes. Our platforms robustness and sensitivity allow the detection of individual-specific variation with high fidelity across batches and plate layouts. Lastly, our models confidently separate LRRK2 and sporadic Parkinsons disease lines from healthy controls (receiver operating characteristic area under curve 0.79 (0.08 standard deviation)), supporting the capacity of this platform for complex disease modeling and drug screening applications.

cell biology↗

bioRxiv2020

An altered cognitive strategy associated with reduction of synaptic inhibition in the prefrontal cortex after social play deprivation in rats

Sensory driven activity during early life is critical for setting up the proper connectivity of the sensory cortices. Here we ask if social play behavior, a particular form of social interaction that is highly abundant during post-weaning development, is equally important for setting up connections in the developing prefrontal cortex (PFC). Young rats were deprived from social play with peers for 3 weeks during the period in life when social play behavior normally peaks (P21-42; SPD rats), followed by resocialization until adulthood. We recorded synaptic currents in L5 cells in slices from medial PFC of adult SPD and control rats and observed that inhibitory synaptic currents were reduced in SPD slices, while excitatory synaptic currents were unaffected. This was associated with a decrease in perisomatic inhibitory synapses from parvalbumin-positive GABAergic cells. In parallel experiments, adult SPD rats achieved more reversals in a probabilistic reversal learning task (PRL), which depends on the integrity of the PFC. They appeared to use a different cognitive strategy than controls. One hour of intense play during SPD did not prevent the decrease in inhibitory synaptic inputs and had only a limited effect on behavioral outcomes in the PRL. Our data demonstrate the importance of unrestricted social play for the development of inhibitory synapses in the PFC and cognitive skills in adulthood.

neuroscience↗

bioRxiv2019

Wnt Regulation: Exploring Axin-Disheveled interactions and defining mechanisms by which the SCF E3 ubiquitin ligase is recruited to the destruction complex

Wnt signaling plays key roles in embryonic development and adult stem cell homeostasis, and is altered in human cancer. Signaling is turned on and off by regulating stability of the effector {beta}-catenin. The multiprotein destruction complex binds and phosphorylates {beta}-catenin, and transfers it to the SCF-TrCP E3-ubiquitin ligase, for ubiquitination and destruction. Wnt signals act though Dishevelled to turn down the destruction complex, stabilizing {beta}-catenin. Recent work clarified underlying mechanisms, but important questions remain. We explore {beta}-catenin transfer from the destruction complex to the E3 ligase, and test models suggesting Dishevelled and APC2 compete for association with Axin. We find that Slimb/TrCP is a dynamic component of the destruction complex biomolecular condensate, while other E3 proteins are not. Recruitment requires Axin and not APC, and Axins RGS domain plays an important role. We find that elevating Dishevelled levels in Drosophila embryos has paradoxical effects, promoting the ability of limiting levels of Axin to turn off Wnt signaling. When we elevate Dishevelled levels, it forms its own cytoplasmic puncta, but these do not recruit Axin. SIM imaging in mammalian cells suggests that this may result by promoting Dishevelled: Dishevelled interactions at the expense of Dishevelled:Axin interactions when Dishevelled levels are high.

cell biology↗