Biology subjects

Beaumont, M.

Publications and source records attributed to Beaumont, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Engineering Outstanding Water Retention and Toughness through Gradient Cellular Architecture and Delignification: A Case Study of Palm Fronds

Delignification can engineer wood into high-performance multi-scaled materials, building up from its elementary fibrils of nanocellulose across its micro-scaled cellular architecture. However, the potential to engineer other, structurally diverse, non-woody biomass remains largely unexplored. Non-wood plants can add additional hierarchical structures at the mm- and cm-scale. Here, we explore such unique hierarchical architecture as found in date palm fronds, where the vasculature promotes the formation of near-mm scaled vasculature bundles. We also show that along the growth direction, the multi-scale structure varies substantially, i.e. considering the frond base, petiole, and rachis. These tissues are systematically investigated to establish correlations between cellular structure, delignification pathways, and the combination of water dynamics to mechanical performance. A range of property spaces are showcased, highlighting excellent water-storage capacity (~1212%) in the never-dried porous state and high toughness after air-dry densification. Alkaline, acidic-bleaching, and combined bleach-cold alkali treatments are employed to tailor chemical composition and microstructure selectively. The combined route facilitates nanocellulose liberation and redistribution, generating a hierarchical network that improves moisture retention. These findings establish a structure-processing-property relationship for unconventional plant ultra-structure biomass towards multi-scaled materials with unique features from the nano- to the cm-scales.

plant biology↗

bioRxiv2025

The ongoing invasion of the endogenous retrovirus Kuruka in natural Drosophila melanogaster populations

Transposable elements are mobile DNA sequences capable of proliferating within host genomes, occasionally capable of crossing species boundaries via horizontal transfer (HT). Here, we report the discovery and characterization of Kuruka, a newly invading endogenous retrovirus in natural D. melanogaster populations. Kuruka encodes an envelope protein and belongs to the gypsy /gypsy superfamily. Analysis of over 1000 D. melanogaster genomes revealed that Kuruka first appeared in sub-Saharan Africa in 2010. By 2017-2019 Kuruka had spread to Asia, Europe and America in 2017-2019, and is still actively invading Europe and Oceania as of 2021. Phylogenomic analyses suggest that Kuruka entered in D. melanogaster via a recent HT from an Afrotropical Drosophila species, most likely D. erecta. This is the first case of a recent HT from an Afrotropical donor species to D. melanogaster. In D. erecta, Kuruka has a single genomic insertion, which is located within flamenco, a master regulator of TE activity. The presence of an active host defense (piRNAs) suggests that Kuruka is silenced in D. erecta. Our findings establish Kuruka as a valuable model for studying the early stages of TE invasions and the dynamics of genome defense in real time.

genomics↗

bioRxiv2025

Disruption of IgA-mediated aggregation at weaning favors mucus encroachment by commensal bacteria

Disruption of the gut mucus barrier is a critical step in the development of infec-tious or chronic inflammatory diseases. However, there are no clear links between developmental stages, diet, and the mechanical and biochemical properties of mucus. The transition from suckling to weaning is a pivotal stage in the devel-opment of the mucus barrier in mammals, with significant implications for the health and morbidity of mammalian infants. Here, using a novel microfluidic device, we investigate the penetration and organizational properties of motile Escherichia coli bacteria at the mucus interface using purified intestinal mucus collected from cohorts of piglets before and after weaning. In weaned piglets, E. coli penetrate more than 100 {micro}m into the mucus, a distance greater than the physiological thickness of the mucus layer in vivo. In contrast, for suckling piglets significant bacterial aggregation is observed at the interface, hindering the pene-tration process. Using the supernatant obtained from purified mucus of suckling piglets, we were able to restore bacterial aggregation in weaned piglet mucus and limit penetration. Interestingly, we also achieved the same result using purified human breast milk immunoglobulin A (IgA), which is known to promote bacterial aggregation. Our results emphasize the importance of mucosal immunoglobulin A (IgA) specificity in relation to the mothers immunological history, which is primarily transmitted through breast milk and lost during weaning. This also might explain why the suckling/weaning transition is, among other issues, a crit-ical window associated with a high incidence of gastrointestinal infections, before autologous IgA-mediated definite protection is acquired. Studying bacterial pen-etration in complex fluids using this new in vitro microfluidic device will pave the way for future research and the development of predictive tools for use in medical research trials.

microbiology↗

bioRxiv2025

Single cell transcriptomics reveals that air-liquid interface culture promotes goblet cell differentiation and inhibits glycolysis in cell monolayers derived from rabbit caecum organoids

Faithfully recapitulating the cellular heterogeneity of the intestinal epithelium is essential when using organoid models. Air-liquid interface (ALI) culture has been shown to promote secretory cell differentiation but its impact on gene expression in each epithelial cell type remains unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to characterize the cellular heterogeneity of rabbit caecum-derived organoid monolayers grown under immerged or ALI conditions. We then compared these organoid cell type-specific gene expression profiles to a scRNA-seq atlas of the rabbit caecal epithelium in vivo. We selected the rabbit model notably because, unlike mice, it possesses BEST4+ epithelial cells, a newly discovered subset of mature absorptive cells. Our analysis revealed a high degree of transcriptomic similarity between in vivo and organoid-derived stem and transit-amplifying cells. ALI culture markedly enhanced the differentiation of the secretory lineage, especially goblet cells, which transcriptome closely resembled that of in vivo goblet cells. Furthermore, ALI was the only condition allowing the detection of enteroendocrine cells. BEST4+ cells, however, were absent from organoids in immerged or ALI conditions despite their presence in vivo. In addition, ALI culture led to a consistent downregulation of hypoxia and glycolysis-associated genes across all cell types, which suggests a metabolic shift likely driven by increased oxygen availability in ALI conditions. Cell-cell communication analyses further indicated that bone morphogenic protein (BMP) and fibroblast growth factor (FGF) signaling under ALI more closely mirrored in vivo patterns than under immerged condition. Altogether, these results demonstrate that ALI culture allows to better recapitulate the in vivo cellular heterogeneity and molecular signatures of the rabbit intestinal epithelium. Future optimization of culture conditions could enhance the physiological relevance of this organoid model, for instance by delivering oxygen exclusively to the basal side, as occurs in vivo.

cell biology↗

bioRxiv2025

The gut microbiota metabolite isovalerate enhances the epithelial barrier function in cell monolayers derived from porcine ileum organoids

The gut microbiota produces numerous metabolites that influence the epithelial barrier function. Bacterial catabolism of amino acids produces a wide variety of metabolites whose effects on the intestinal epithelium remain to be fully identified. In this study, we investigated the effects of amino acid derived metabolites (isovalerate, isobutyrate, 2-methylbutyrate, 5-aminovalerate, cadaverine, putrescine, and tryptamine) in cell monolayers derived from porcine ileum organoids. Our results show that the leucine-derived branched-chain fatty acid (BCFA) isovalerate improved the epithelial barrier function, as assessed by transepithelial electrical resistance measurement and permeability assay. Isovalerate upregulated the expression of genes involved in innate immunity, markers of absorptive cells and enteroendocrine cells while reducing the expression of the stem cells and mucus related genes. Most of the effects of isovalerate on epithelial cells were also observed with the bacterial metabolite butyrate, an inhibitor of the epigenetic enzymes histone deacetylases (HDAC). Furthermore, the structurally unrelated HDAC inhibitor trichostatin A improved epithelial barrier function and upregulated SLPI gene expression, as observed with isovalerate and butyrate. Isovalerate also upregulated the gene expression of antioxidant enzymes and this effect was not observed with butyrate. Interestingly, the other two BCFAs isobutyrate and 2-methylbutyrate did not replicate the effects of isovalerate, suggesting that the carbon chain structure of isovalerate mediates its effect. In contrast, we found that all three BCFAs were able to cross the epithelial cell monolayer derived from porcine ileum organoids from the apical to the basal side. Overall, our in vitro results suggest that targeting the bacterial production of isovalerate may be useful to promote gut health. In this perspective, we performed an in silico analysis that identified species belonging to dominant gut microbiota genera such as Prevotella, Blautia, Christensenella, Clostridium, and Ruminococcus, as potential producers of BCFAs through the PorA enzymatic pathway.

cell biology↗

bioRxiv2025

Rapid emergence of hyperparasitic elements may stop P-element invasions in the absence of a piRNA-based host defence

Transposable element (TE) invasions pose risks to both the TE and the host. All copies of a TE may be lost via genetic drift, or host populations may suffer fitness declines, potentially leading to extinction. By monitoring invasions of the P-element in experimental D. melanogaster populations for over 100 generations, we uncovered a novel risk for invading TEs. In two replicate populations, the P-element rapidly multiplied until a piRNA-based host defence emerged, leading to the plateauing of TE copy numbers. However, in one population (R2), P-element copy numbers stabilised at a significantly lower level, despite the absence of a piRNA-based host defence. We find that this stabilisation was likely driven by the propagation of non-autonomous insertions, characterised by internal-deletions, which out-competed the autonomous full-length insertions. Such a rapid proliferation of non-autonomous insertions could account for the high prevalence of P-element insertions with internal-deletions observed in natural D. melanogaster populations. Our work reveals that TEs may stochastically sabotage their own spread in populations due to the emergence of hyperparasites, rendering the establishment of a host defence unnecessary. The proliferation of hyperparasitic elements may also lead into an evolutionary dead end, where affected populations are resistant to re-invasion (e.g. following recurrent horizontal transfer), yet are unable to infect other species due to a lack of autonomous insertions.

genetics↗

bioRxiv2024

A single-cell atlas of transcriptome changes in the intestinal epithelium at the suckling-to-weaning transition

The suckling-to-weaning dietary transition is a key step in mammalian intestinal development. However, the relative contributions of genetically wired and nutritional factors in this maturation process remain to be elucidated. Moreover, the cellular diversity of the intestinal epithelium has been overlooked in this context. The aim of our study was to identify the transcriptome changes induced in each cell type of the intestinal epithelium at the onset of solid food ingestion. We compared the single-cell transcriptome of epithelial cells isolated from the caecum of age-matched littermate suckling rabbits ingesting or not solid food. Our dataset provides the first single-cell atlas of the rabbit intestinal epithelium and highlights the interest of the rabbit as a model for studying BEST4+ epithelial cells, which are absent in mice. Solid food ingestion induced extensive transcriptome changes in each epithelial cell type, with the most pronounced changes noted in absorptive and BEST4+ cells. Some of the effects of solid food introduction were common to most epithelial cell types, such as the upregulation of ALDH1A1, which encodes for a vitamin A processing enzyme. Solid food ingestion remodeled epithelial defenses systems, as observed by the increased expression of interferon-stimulated genes in mature absorptive and BEST4+ cells. Solid food also upregulated the gene expression of the immunoglobulin transporter PIGR, specifically in cells located at the base of epithelial crypts and in goblet cells. In addition, solid food triggered epithelial differentiation, which was associated with modification of the expression of genes involved in handling of amino acids, lipids and bile acids, as well as changes in hormone expression by enteroendocrine cells. These cell type-specific transcriptome modifications induced by solid food ingestion coincided with changes in microbiota composition and metabolic activity, which may contribute to epithelial maturation. Overall, our work provides a single-cell atlas of the transcriptome changes induced in the intestinal epithelium at the suckling-to-weaning transition.

physiology↗

bioRxiv2024

Seabird and sea duck mortalities were lower during the second breeding season in eastern Canada following the introduction of Highly Pathogenic Avian Influenza A H5Nx viruses

H5N1 clade 2.3.4.4b viruses have caused significant mortality events in various wild bird species across Europe, North America, South America, and Africa. In North America, the largest impacts on wild birds have been in eastern Canada, where over 40,391 wild birds were reported to have died from highly pathogenic avian influenza (HPAI) between April and September 2022. In the year following, we applied previously established methods to quantify total reported mortality in eastern Canada for a full year October 2022, to September 2023. In this study, we (i) document the spatial, temporal and taxonomic patterns of wild bird mortality in the 12 months that followed the mass mortality event in the summer of 2022 and (ii) quantify the observed differences in mortality across the breeding season (April to September) of 2022 and 2023. In eastern Canada, there was high uncertainty about whether 2023 would bring another year of devastating HPAI-linked mortalities. Mortalities in the breeding season were 93% lower in 2023 compared to 2022 but encompassed a more taxonomically diverse array of species. We found that mortalities in the fall and winter (non-breeding season) were dominated by waterfowl, while mortalities during the spring and summer (breeding season) were dominated by seabirds. Due to a low prevalence of HPAI among the subset of tested birds, we refrained from broadly attributing reported mortalities in 2023 to HPAI. However, our analysis did identify three notable mortality events linked to HPAI, involving at least 1,646 Greater Snow Geese, 232 Canada Geese, and 212 Northern Gannets. This study emphasizes the ongoing need for H5NX surveillance and mortality assessments as the patterns of mortality in wild populations continue to change.

ecology↗

bioRxiv2024

Wild bird mass mortalities in eastern Canada associated with the Highly Pathogenic Avian Influenza A(H5N1) virus, 2022

In 2022, a severe outbreak of clade 2.3.4.4b Highly Pathogenic Avian Influenza (HPAI) H5N1 virus resulted in unprecedented mortality among wild birds in eastern Canada. Tens of thousands of birds were reported sick or dead, prompting a comprehensive assessment of mortality spanning the breeding season between April 1 and September 30, 2022. Mortality reports were collated from federal, Indigenous, provincial, and municipal agencies, the Canadian Wildlife Health Cooperative, non-governmental organizations, universities, and citizen science platforms. A scenario analysis was conducted to refine mortality estimates, accounting for potential double counts from multiple sources under a range of spatial and temporal overlap. Correcting for double counting, an estimated 40,966 wild birds were reported sick or dead in eastern Canada during the spring and summer of 2022. Seabirds and sea ducks, long-lived species that are slow to recover from perturbations, accounted for 98.7% of reported mortalities. Mortalities were greatest among Northern Gannets (Morus bassanus; 26,193), Common Murres (Uria aalge; 8,133), and American Common Eiders (Somateria mollissima dresseri; 1,945), however, these figures underestimate total mortality as they exclude unreported deaths on land and at sea. In addition to presenting mortality estimates, we compare mortalities with known population sizes and trends and make an initial assessment of whether population-level impacts are possible for the Northern Gannet, a species that has suffered significant global mortality, and two harvested species, Common Murre and American Common Eider, to support management decisions. We hypothesize that population-level impacts in eastern Canada are possible for Northern Gannets and American Common Eiders but are unlikely for Common Murres. This study underscores the urgent need for further research to understand the broader ecological ramifications of the HPAI outbreak on wild bird populations.

zoology↗

bioRxiv2023

Estimating temporally variable selection intensity from ancient DNA data II

Recent technological innovations, such as next generation sequencing and DNA hybridisation enrichment, have made it possible to recover DNA information from historical and archaeological biological materials, which has motivated the development of various statistical approaches for inferring selection from allele frequency time series data. Recently, He et al. (2023a,b) introduced methods that can utilise ancient DNA (aDNA) data in the form of genotype likelihoods, therefore enabling the modelling of sample uncertainty arising from DNA molecule damage and fragmentation. However, their performance suffers from the underlying dependency on the allele age. Here we introduce a novel particle marginal Metropolis-Hastings within Gibbs framework for Bayesian inference of time-varying selection from aDNA data in the form of genotype like-lihoods. To circumvent the performance issue encountered in He et al. (2023a,b), we devise a novel numerical scheme for backward-in-time simulation of the Wright-Fisher diffusion and mix forward- and backward-in-time simulations in the particle filter for likelihood computation. Our framework also enables us to reconstruct the underlying population allele frequency trajectories, integrate temporal information in genotype likelihood calculations and test hypotheses on the drivers of past selection events. We conduct extensive evaluations through simulations and show its utility with an application to aDNA data from pigmentation loci in ancient horses.

genetics↗

bioRxiv2022

Stronger transcriptomic response to feed intake in the duodenum of pig with high feed efficiency from a divergent selection experiment

Feed efficiency is a trait of interest in pigs as it contributes to lowering the ecological and economical costs of pig production. A divergent genetic selection experiment from a Large White pig population was performed for 10 generations, leading to pig lines with relative low-(LRFI, more efficient) and high-(HRFI, less efficient) residual feed intake (RFI). Feeding behaviour and metabolic differences have been previously reported between the two lines. We hypothesised that part of these differences could be related to differential sensing and absorption of nutrients in the proximal intestine. Here we investigated the duodenum transcriptome and DNA methylation profiles comparing overnight fasting with ad libitum feeding in LRFI and HRFI pigs (n=24). We identified 1,106 differentially expressed genes between the two lines, notably affecting pathways of the transmembrane transport activity and related to mitosis or chromosome separation. The LRFI line showed a greater transcriptomic response to feed intake, with 2,222 differentially expressed genes before and after a meal, as compared to 61 differentially expressed genes in the HRFI line. Feed intake affected genes from both anabolic and catabolic pathways in the pig duodenum, such as rRNA production and autophagy. We noted that several nutrient transporter and tight junction genes were differentially expressed between lines and/or by short term feed intake. We also identified 409 differentially methylated regions in the duodenum mucosa between the two lines, while this epigenetic mark was less affected by feeding. However most of the differentially expressed genes were not associated with proximal changes in DNA methylation profiles. Altogether, our findings highlighted that the genetic selection for feed efficiency in pigs changed the transcriptome profiles of the duodenum, and notably its response to feed intake, suggesting key roles for this proximal gut segment in mechanisms underlying feed efficiency.

genomics↗

bioRxiv2022

Estimating temporally variable selection intensity from ancient DNA data with the flexibility of modelling linkage and epistasis

Innovations in ancient DNA (aDNA) preparation and sequencing technologies have exponentially increased the quality and quantity of aDNA data extracted from ancient biological materials. The additional temporal component from the incoming aDNA data can provide improved power to address fundamental evolutionary questions like characterising selection processes that shape the phenotypes and genotypes of contemporary populations or species. However, utilising aDNA to study past selection processes still involves considerable hurdles like how to eliminate the confounding factor of genetic interactions in the inference of selection. To address this issue, we extend the approach of He et al. (2022) to infer temporally variable selection from the aDNA data in the form of genotype likelihoods with the flexibility of modelling linkage and epistasis in this work. Our posterior computation is carried out by a robust adaptive version of the particle marginal Metropolis-Hastings algorithm with a coerced acceptance rate. Our extension inherits the desirable features of He et al. (2022) such as modelling sample uncertainty resulting from the damage and fragmentation of aDNA molecules and reconstructing underlying gamete frequency trajectories of the population. We evaluate its performance through extensive simulations and show its utility with an application to the aDNA data from pigmentation loci in horses.

genetics↗

bioRxiv2022

Estimating temporally variable selection intensity from ancient DNA data

Novel technologies for recovering DNA information from archaeological and historical specimens have made available an ever-increasing amount of temporally spaced genetic samples from natural populations. These genetic time series permit the direct assessment of patterns of temporal changes in allele frequencies, and hold the promise of improving power for the inference of selection. Increased time resolution can further facilitate testing hypotheses regarding the drivers of past selection events such as the incidence of plant and animal domestication. However, studying past selection processes through ancient DNA (aDNA) still involves considerable obstacles such as postmortem damage, high fragmentation, low coverage and small samples. To circumvent these challenges, we introduce a novel Bayesian framework for the inference of temporally variable selection based on genotype likelihoods instead of allele frequencies, thereby enabling us to model sample uncertainties resulting from the damage and fragmentation of aDNA molecules. Also, our approach permits the reconstruction of the underlying allele frequency trajectories of the population through time, which allows for a better understanding of the drivers of selection. We evaluate its performance through extensive simulations and demonstrate its utility with an application to the ancient horse samples genotyped at the loci for coat colouration. Our results reveal that incorporating sample uncertainties can further improve the inference of selection.

genetics↗

bioRxiv2021

Statistical inference in population genomics

The field of population genomics has grown rapidly in response to the recent advent of affordable, large-scale sequencing technologies. As opposed to the situation during the majority of the 20th century, in which the development of theoretical and statistical population-genetic insights out-paced the generation of data to which they could be applied, genomic data are now being produced at a far greater rate than they can be meaningfully analyzed and interpreted. With this wealth of data has come a tendency to focus on fitting specific (and often rather idiosyncratic) models to data, at the expense of a careful exploration of the range of possible underlying evolutionary processes. For example, the approach of directly investigating models of adaptive evolution in each newly sequenced population or species often neglects the fact that a thorough characterization of ubiquitous non-adaptive processes is a prerequisite for accurate inference. We here describe the perils of these tendencies, present our consensus views on current best practices in population genomic data analysis, and highlight areas of statistical inference and theory that are in need of further attention. Thereby, we argue for the importance of defining a biologically relevant baseline model tuned to the details of each new analysis, of skepticism and scrutiny in interpreting model-fitting results, and of carefully defining addressable hypotheses and underlying uncertainties.

evolutionary biology↗

bioRxiv2021

Inferring the timing and strength of natural selection and gene migration in the evolution of chicken from ancient DNA data

With the rapid growth of the number of sequenced ancient genomes, there has been increasing interest in using this new information to study past and present adaptation. Such an additional temporal component has the promise of providing improved power for the estimation of natural selection. Over the last decade, statistical approaches for detection and quantification of natural selection from ancient DNA (aDNA) data have been developed. However, most of the existing methods do not allow us to estimate the timing of natural selection along with its strength, which is key to understanding the evolution and persistence of organismal diversity. Additionally, most methods ignore the fact that natural populations are almost always structured, which can result in overestimation of the effect of natural selection. To address these issues, we introduce a novel Bayesian framework for the inference of natural selection and gene migration from aDNA data with Markov chain Monte Carlo techniques, co-estimating both timing and strength of natural selection and gene migration. Such an advance enables us to infer drivers of natural selection and gene migration by correlating genetic evolution with potential causes such as the changes in the ecological context in which an organism has evolved. The performance of our procedure is evaluated through extensive simulations, with its utility shown with an application to ancient chicken samples.

genetics↗

bioRxiv2020

Functional maturation of the gut microbiota at weaning is influenced by maternal environment in piglets

The objective of this study was to analyze in piglets the impact of weaning on the production of metabolites by gut bacteria and to determine whether early life environment influences the functional maturation of the gut microbiota. Fecal metabolome and microbiome were analyzed in piglets raised in two separate maternity farms and mixed at weaning. In piglets from both maternity farms, the relative abundance of Lactobacillus and of the predicted function "Fucose degradation" decreased after weaning while the relative abundance of Ruminococcus 2 and of the predicted function "Starch degradation" increased. In piglets from the first maternity farm, the relative concentration of biogenic amines and the relative abundance of Escherichi-Shigella decreased after weaning while the relative concentration of short chain fatty acids and the relative abundance of Christensenellaceae R-7 group and Ruminococcaceae UCG-002 increased. These changes were not observed at weaning in piglets from the second maternity farm probably because they already had high relative concentration of short chain fatty acids and higher relative abundance of Christensenellaceae R-7 group and Ruminococcaceae UCG-002 during the suckling period. In conclusion, the functional maturation of the microbiota at weaning is highly dependent on the maternal environment in piglets. ORIGINALITY - SIGNIFICANCE STATEMENTBacterial metabolites are key molecular intermediates between the gut microbiota and host cells. Our study in piglets reveals that the metabolic activity of the gut microbiota shifts at weaning, a key developmental period for intestinal and immune health. We also show that this functional maturation of the gut microbiota is strongly influenced by maternal environment. Thus, targeting early life environmental factors is a promising strategy to program health trough the production of beneficial bacterial metabolites at the suckling-to-weaning transition.

microbiology↗

bioRxiv2020

Reconstitution of intestinal stem cell niche in vitro with pharmacological inhibitors or L-WRN conditioned medium differentially regulates epithelial proliferation, differentiation and barrier function in rabbit caecum organoids

Intestinal organoids are self-organized 3-dimensional (3D) structures formed by a single layer of polarized epithelial cells. This innovative in vitro model is highly relevant to study physiology of the intestinal epithelium and its role in nutrition and barrier function. However, this model has never been developed in rabbits, while it would have potential applications for biomedical and veterinary research. Here, we cultured rabbit caecum organoids with either pharmacological inhibitors (2Ki medium) or L-WRN cells conditioned medium (L-WRN CM) to reconstitute the intestinal stem cell niche in vitro. Large spherical organoids were obtained with the 2Ki medium and this morphology was associated with a high level of proliferation and stem cells markers gene expression. In contrast, organoids cultured with L-WRN CM had a smaller diameter; a greater cell height and part of them were not spherical. When the L-WRN CM was used at low concentration (5%) for two days, the gene expression of stem cells and proliferation markers were very low, while absorptive and secretory cells markers and antimicrobial peptides were elevated. Epithelial cells within organoids were polarized in 3D cultures with 2Ki medium or L-WRN CM (apical side towards the lumen). We cultured dissociated organoid cells in 2D monolayers, which allowed accessibility to the apical compartment. Under these conditions, actin stress fibers were observed with the 2Ki medium, while perijonctionnal localization of actin was observed with the L-WRN CM suggesting, in 2D cultures as well, a higher differentiation level in the presence of L-WRN CM. In conclusion, rabbit caecum organoids cultured with the 2Ki medium were more proliferative and less differentiated than organoids cultured with L-WRN CM. We propose that organoids cultured with the 2Ki medium could be used to rapidly generate in vitro a large number of rabbit intestinal epithelial stem cells while organoids cultured with the L-WRN CM represent a suitable model to study differentiated rabbit epithelium.

cell biology↗

bioRxiv2020

The paradoxical effects of K+ channel gain-of-function are mediated by GABAergic neuron hypoexcitability and hyperconnectivity.

Gain-of-function (GOF) variants in K+ channels cause severe childhood epilepsies, but there are no mechanisms to explain how increased K+ currents lead to network hyperexcitability. Here, we introduced a human Na+-activated K+ (KNa) channel variant (KCNT1-Y796H) into mice and, using a multiplatform approach, found motor cortex hyperexcitability and early-onset seizures, phenotypes strikingly similar to those of human patients. Although the variant increased KNa currents in cortical excitatory and inhibitory neurons, there was a selective increase in the KNa current across subthreshold voltages in inhibitory neurons, particularly in those with non-fast spiking properties, resulting in impaired excitability and AP generation. We further observed evidence of synaptic rewiring associated with hyperexcitable networks, including increases in homotypic synaptic connectivity and the ratio of excitatory-to-inhibitory synaptic input. These findings support inhibitory neuron-specific mechanisms in mediating the epileptogenic effects of K+ channel GOF, offering cell-type-specific currents and effects as promising targets for therapeutic intervention. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/978841v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@110d6e1org.highwire.dtl.DTLVardef@8b63ddorg.highwire.dtl.DTLVardef@14972a9org.highwire.dtl.DTLVardef@106be1c_HPS_FORMAT_FIGEXP M_FIG GRAPHICAL ABSTRACT C_FIG

neuroscience↗