Biology subjects

Mayer, C.

Publications and source records attributed to Mayer, C..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Nfib regulates progenitor competence in maturation of GABAergic neurons

Diverse types of GABAergic projection neurons and interneurons of the telencephalon derive from progenitors in a ventral germinal zone, called the ganglionic eminence. Using single-cell transcriptomics, chromatin accessibility profiling, lineage tracing, birthdating, heterochronic transplantation, and perturbation sequencing in mouse embryos, we investigated how progenitor competence influences the maturation and differentiation of these neurons. We found that the progression of neurogenesis over developmental time shapes maturation competence in ganglionic eminence progenitors, influencing how they progress into mature states. In contrast, differentiation competence, which defines the ability to produce diverse transcriptomic identities, remains largely unaffected by the stages of neurogenesis. Chromatin remodeling alongside a NFIB-driven regulatory gene module influences maturation competence in late-born neurons. These findings provide key insights into how transcriptional programs and chromatin accessibility govern neuronal maturation and the diversification of GABAergic neuron subtypes during neurodevelopment.

neuroscience↗

bioRxiv2024

Direct excitatory synapses between neurons and tumor cells drive brain metastatic seeding of breast cancer and melanoma

Interactions between neurons and cancer cells are found in many malignancies, but their relevance for metastatic organ colonization remain largely unknown. It is also unclear whether any direct synaptic communication between neurons and cancer cells of non-neural tumor types exists, and if so, whether this can support metastasis and thus cancer progression. Here we show that excitatory synapses are formed between neurons and brain-metastatic melanoma and breast cancer cells. This starts at an early microscopic stage after extravasation into the brain parenchyma, during residence of cancer cells in the perivascular niche, a critical step for their survival. These neuron-cancer synapses showed a bona fide synaptic ultrastructure, and generated excitatory postsynaptic currents mediated by glutamate receptors of the AMPA subtype in cancer cells. In accordance, AMPA receptor signatures were consistently detected in preclinical and patient samples of melanoma and breast cancer brain metastases. Genetic perturbation and pharmacological inhibition of AMPA receptors with the approved antiepileptic drug perampanel in models of breast and melanoma cancer reduced the number of brain metastases and overall brain metastatic burden. These findings demonstrate for the first time that neurons can form biologically relevant direct synapses with non-neural cancer cells. In brain metastasis, a particularly challenging complication of many common malignancies, this non-canonical stimulatory synaptic interaction offers novel therapeutic opportunities.

cancer biology↗

bioRxiv2023

Phylogenomics recovers multiple origins of portable case-making in caddisflies (Insecta: Trichoptera), the world's most common underwater architects

Caddisflies (Trichoptera) are among the most diverse groups of freshwater animals with more than 16,000 described species. They play an outsized role in freshwater ecology and environmental engineering in streams, rivers, and lakes. Because of this, they are frequently used as indicator organisms in biomonitoring programs. Despite their importance, key questions concerning the evolutionary history of caddisflies, such as the timing and origin of larval case-making, have been unanswered due to the lack of a well-resolved phylogenetic tree. To shed light on these questions in Trichoptera, we estimated a phylogenetic tree using a combination of transcriptomes and targeted enrichment data for 206 species, representing 48 of 52 extant families and 174 genera. We calibrated and dated the tree with a set of 33 carefully selected fossils. The first caddisflies originated in the Permian and the major suborders began to diversify in the Triassic. Ancestral state reconstruction and diversification analysis revealed that portable case-making evolved in three separate lineages and shifts in diversification occurred in concert with key evolutionary innovations other than case-making.

evolutionary biology↗

bioRxiv2023

A robust life-or-death selection platform for enzyme evolution

Life-or-death selections evaluate the fitness of individual organisms on a population level. In enzyme engineering, such growth selections allow the rapid and straightforward identification of highly efficient biocatalysts from extensive libraries. However, selection-based improvement of (industrially-relevant) biocatalysts is challenging, as they require highly dependable strategies that artificially link their activities to host survival. Here, we showcase a robust and scalable life-or-death selection platform centered around the complementation of non-canonical amino acid-dependent bacteria. Specifically, we demonstrate how serial passaging of populations featuring millions of carbamoylase variants autonomously selects biocatalysts with up to 90,000-fold higher initial rates. Notably, selection of replicate populations enriched diverse biocatalysts, which feature distinct amino-acid motifs that drastically boost carbamoylase activity. As beneficial substitutions also originated from unintended copying errors during library preparation or cell division, we anticipate that our life-or-death selection platform will be applicable to the continuous, autonomous evolution of diverse biocatalysts in the future.

synthetic biology↗

bioRxiv2023

Dual lineage origins of neocortical astrocytes

Astrocytes represent one of the most abundant cell types in the central nervous system, and play an essential role in nearly all aspects of brain functions1. Recent studies have challenged the notion that cortical astrocytes are a uniform population, and have highlighted their diverse characteristics at the morphological, molecular, and functional levels2-5. However, how this diversity originates and establishes during cortical development, remains largely unknown. Using single-cell RNA sequencing, we identified five distinct astrocyte subtypes displaying unique spatial patterns in the mouse neocortex, and discovered essential regulators for their formation. Furthermore, we used TrackerSeq6, a method that integrates heritable DNA barcodes into the genome of electroporated progenitors, to track clonally related astrocytes, and identified two distinct lineages that give rise to the five astrocyte subtypes. The first lineage derives from Emx1+ multipotent progenitors that first generate neurons and then switch to produce cortical astrocytes. The second lineage stems from a fate-restricted progenitor population that exclusively gives rise to a specific subset of cortical astrocytes, marked by Olig2. The knockout of this gene in cortical progenitors is sufficient to promote a fate switch between the two lineages. These findings offer novel insights into the cellular mechanisms underlying astrocyte diversity, highlighting the presence of multiple progenitor subtypes, responsible for generating distinct subtypes of astrocytes.

neuroscience↗

bioRxiv2023

Wall teichoic acid substitution with glucose governs phage susceptibility of Staphylococcus epidermidis

The species- and clone-specific susceptibility of Staphylococcus cells for bacteriophages is governed by the structures and glycosylation patterns of wall teichoic acid (WTA) glycopolymers. The glycocodes of phage-WTA interaction in the opportunistic pathogen Staphylococcus epidermidis and in other coagulase-negative staphylococci (CoNS) have remained unknown. We report a new S. epidermidis WTA glycosyltransferase TagE whose deletion confers resistance to siphoviruses such as {Phi}E72 but enables binding of otherwise unbound podoviruses. S. epidermidis glycerolphosphate WTA was found to be modified with glucose in a tagE-dependent manner. TagE is encoded together with the enzymes PgcA and GtaB providing uridine diphosphate-activated glucose. {Phi}E72 transduced several other CoNS species encoding TagE homologs suggesting that WTA glycosylation via TagE is a frequent trait among CoNS that permits inter-species horizontal gene transfer. Our study unravels a crucial mechanism of phage-Staphylococcus interaction and of horizontal gene transfer and it will help in the design of anti-staphylococcal phage therapies. ImportancePhages are highly specific for certain bacterial hosts, and some can transduce DNA even across species boundaries. How phages recognize cognate host cells remains incompletely understood. Phages infecting members of the genus Staphylococcus bind to wall teichoic acid (WTA) glycopolymers with highly variable structures and glycosylation patterns. How WTA is glycosylated in the opportunistic pathogen Staphylococcus epidermidis and in other coagulase-negative Staphylococcus (CoNS) species has remained unknown. We describe that S. epidermidis glycosylates its WTA backbone with glucose and we identify a cluster of three genes, responsible for glucose activation and transfer to WTA. Their inactivation strongly alters phage susceptibility patterns, yielding resistance to siphoviruses but susceptibility to podoviruses. Many different CoNS species with related glycosylation genes can exchange DNA via siphovirus {Phi}E72 suggesting that glucose-modified WTA is crucial for interspecies horizontal gene transfer. Our finding will help to develop antibacterial phage therapies and unravel routes of genetic exchange.

microbiology↗

bioRxiv2023

Machine learning can be as good as maximum likelihood when reconstructing phylogenetic trees and determining the best evolutionary model on four taxon alignments

Phylogenetic tree reconstruction with molecular data is important in many fields of life science research. The gold standard in this discipline is the phylogenetic tree reconstruction based on the Maximum Likelihood method. In this study, we explored the utility of neural networks to predict the correct model of sequence evolution and the correct topology for four sequence alignments. We trained neural networks with different architectures using simulated nucleotide and amino acid sequence alignments for a wide range of evolutionary models, model parameters and branch lengths. By comparing the accuracy of model and topology prediction of the trained neural networks with Maximum Likelihood and Neighbour Joining methods, we show that for quartet trees, the neural network classifier outperforms the Neighbour Joining method and is in most cases as good as the Maximum Likelihood method to infer the best model of sequence evolution and the best tree topology. These results are consistent for nucleotide and amino acid sequence data. Furthermore, we found that neural network classifiers are much faster than the IQ-Tree implementation of the Maximum Likelihood method. Our results show that neural networks could become a true competitor for the Maximum Likelihood method in phylogenetic reconstructions.

evolutionary biology↗

bioRxiv2023

A transcriptome-based phylogeny of Scarabaeoidea confirms the sister group relationship of dung beetles and phytophagous pleurostict scarabs (Coleoptera)

Scarab beetles (Scarabaeidae) are a diverse and ecologically important group of angiosperm-associated insects. As conventionally understood, scarab beetles comprise two major lineages: dung beetles and the phytophagous Pleurosticti. However, previous phylogenetic analyses have not been able to convincingly answer the question whether or not the two lineages form a monophyletic group. Here we report our results from phylogenetic analyses of more than 4,000 genes mined from transcriptomes of more than 50 species of Scarabaeidae and other Scarabaeoidea. Our results provide convincing support for the monophyly of Scarabaeidae, confirming the debated sister group relationship of dung beetles and phytophagous pleurostict scarabs. Supermatrix-based maximum likelihood and multispecies coalescent phylogenetic analyses strongly imply the subfamily Melolonthinae as currently understood being paraphyletic. We consequently suggest various changes in the systematics of Melolonthinae: Sericinae Kirby, 1837 stat. rest. and sensu n. to include the tribes Sericini, Ablaberini and Diphucephalini, and Sericoidinae Erichson, 1847 stat. rest. and sensu n. to include the tribes Automoliini, Heteronychini, Liparetrini, Maechidiini, Scitalini, Sericoidini, and Phyllotocini. Both subfamilies appear to consistently form a monophyletic sister group to all remaining subfamilies so far included within pleurostict scarabs except Orphninae. Our results represent a major step towards understanding the diversification history of one of the largest angiosperm-associated radiations of beetles.

zoology↗

bioRxiv2023

A Latent Clinical-anatomical Dimension Relating Metabolic Syndrome to Brain Morphology - Evidence from a Multivariate Imaging Analysis of 40,087 Individuals

The link between metabolic syndrome (MetS) and neurodegenerative as well cerebrovascular conditions holds substantial implications for brain health in at-risk populations. This study elucidates the complex relationship between MetS and brain health by conducting a comprehensive examination of cardiometabolic risk factors, cortical morphology, and cognitive function in 40,087 individuals. Multivariate, data-driven statistics identified a latent dimension linking more severe MetS to widespread brain morphological abnormalities, accounting for up to 71% of shared variance in the data. This dimension was replicable across sub-samples. In a mediation analysis we could demonstrate that MetS-related brain morphological abnormalities mediated the link between MetS severity and cognitive performance in multiple domains. Employing imaging transcriptomics and connectomics, our results also suggest that MetS-related morphological abnormalities are linked to the regional cellular composition and macroscopic brain network organization. By leveraging extensive, multi-domain data combined with a dimensional stratification approach, our analysis provides profound insights into the association of MetS and brain health. These findings can inform effective therapeutic and risk mitigation strategies aimed at maintaining brain integrity.

neuroscience↗

bioRxiv2023

Metabolization of alpha-D-carba-glucosamine in vivo generates antimetabolites of cell wall precursors

-D-Carba-glucosamine (CGlcN) is a carbocyclic analog of -D-glucosamine that inhibits growth of Bacillus subtilis and Staphylococcus aureus. CGlcN is internalized and concomitantly phosphorylated via the phosphotransferase system yielding -D-carba-glucosamine-6-phosphate (CGlcN6P), which interferes with expression of the glutamine-fructose-6-phosphate amidotransferase (GlmS; glucosamine synthase) by activating the glmS riboswitch. Herein, we report that CGlcN6P is efficiently metabolized to carbasugar nucleotides along the peptidoglycan biosynthetic route. Mass spectrometric analysis confirmed the occurrence of carbocyclic peptidoglycan nucleotides UDP-carba-D-N-acetyl-glucosamine (UDP-CGlcNAc) and UDP-carba-D-N-acetylmuramic acid-pentapeptide (UDP-CMurNAc-5P) in the presence of CGlcN and revealed accumulation of these carba-metabolites upon antibiotic treatment interfering with biosynthetic enzyme functions. Thus, carbocyclic carbohydrates and nucleotide analogs are generated by the promiscuous bacterial cell wall biosynthetic enzymes and act as antimetabolites, causing bacterial growth inhibition by interference with cell wall synthesis. Our findings reveal CGlcN not only as putative antibiotic molecule with previously unknown antimetabolite mode of action, but also as tool to study the bacterial cell wall metabolism, e.g., in synergy with other antibiotics.

microbiology↗

bioRxiv2023

Spatial enhancer activation determines inhibitory neuron identity

The mammalian telencephalon contains a tremendous diversity of GABAergic projection neuron and interneuron types, that originate in a germinal zone of the embryonic basal ganglia. How genetic information in this transient structure is transformed into different cell types is not yet fully understood. Using a combination of in vivo CRISPR perturbation, lineage tracing, and ChIP-seq in mice, we found that the transcription factor MEIS2 favors the development of projection neurons through genomic binding sites in regulatory enhancers of projection neuron specific genes. MEIS2 requires the presence of the homeodomain transcription factor DLX5 to direct its functional activity towards these sites. In interneuron precursors, the activation of projection neuron specific enhancers by MEIS2 and DLX5 is repressed by the transcription factor LHX6. When MEIS2 carries a mutation associated with intellectual disability in humans, it is less effective at activating enhancers involved in projection neuron development. This suggests that GABAergic differentiation may be impaired in patients carrying this mutation. Our research supports a model ("Differential Binding ) where the spatial specific composition of transcription factors at cis-regulatory elements determines differential gene expression and cell fate decisions in the ganglionic eminence.

developmental biology↗

bioRxiv2022

Transcriptomics reveals amygdala neuron regulation by fasting and ghrelin thereby promoting feeding

The central amygdala (CeA) consists of numerous genetically-defined inhibitory neurons that control defensive and appetitive behaviors including feeding. Transcriptomic signatures of cell types and their links to function remain poorly understood. Using single-nucleus RNA-sequencing, we describe nine CeA cell clusters, of which four are mostly associated with appetitive and two with aversive behaviors. To analyze the activation mechanism of appetitive CeA neurons, we characterized Serotonin receptor 2a (Htr2a)-expressing neurons (CeAHtr2a) that comprise three appetitive clusters and were previously shown to promote feeding. In vivo calcium imaging revealed that CeAHtr2a neurons are activated by fasting, the hormone ghrelin, and the presence of food. Moreover, these neurons are required for the orexigenic effects of ghrelin. Appetitive CeA neurons responsive to fasting and ghrelin project to the parabrachial nucleus (PBN) causing inhibition of target PBN neurons. These results illustrate how the transcriptomic diversification of CeA neurons relates to fasting and hormone-regulated feeding behavior. HighlightsTranscriptomics reveals four appetitive, two aversive and three unknown CeA clusters Ghrelin and fasting activate CeAHtr2a neurons comprising three appetitive clusters Ghrelins orexigenic effects require the activity of appetitive CeA neurons CeA[->]PBN inhibition is necessary for ghrelin/fasting induced feeding

neuroscience↗

bioRxiv2022

Selecting better biocatalysts by complementing recoded bacteria

In vivo selections are powerful tools for the directed evolution of enzymes. However, the need to link enzymatic activity to cellular survival makes selections for enzymes that do not fulfill a metabolic function challenging. Here, we present an in vivo selection strategy that leverages recoded organisms addicted to non-canonical amino acids (ncAAs) to evolve biocatalysts that can provide these building blocks from synthetic precursors. We exemplify our platform by engineering carbamoylases that display catalytic efficiencies more than five orders of magnitude higher than those observed for the wild-type enzyme for ncAA-precursors. As growth rates of bacteria under selective conditions correlate with enzymatic activity, we were able to elicit improved variants from populations by performing serial passaging. By requiring minimal human intervention and no specialized equipment, we surmise that our strategy will become a versatile tool for the in vivo directed evolution of diverse biocatalysts.

synthetic biology↗

bioRxiv2022

Brain Network Architecture Constrains Age-related Cortical Thinning

Age-related cortical atrophy, approximated by cortical thickness measurements from magnetic resonance imaging, follows a characteristic pattern over the lifespan. Although its determinants remain unknown, mounting evidence demonstrates correspondence between the connectivity profiles of structural and functional brain networks and cortical atrophy in health and neurological disease. Here, we performed a cross-sectional multimodal neuroimaging analysis of 2633 individuals from a large population-based cohort to characterize the association between age-related differences in cortical thickness and functional as well as structural brain network topology. We identified a widespread pattern of age-related cortical thickness differences including "hotspots" of strong age effects located in brain areas with high centrality (structural network hubs). Regional age-related differences were furthermore strongly correlated within the structurally defined node neighborhood. The overall pattern of thickness differences as well as its change throughout the later lifespan was found to be anchored in the functional network hierarchy as encoded by macroscale functional connectivity gradients. Lastly, the identified difference pattern covaried significantly with cognitive and motor performance. Our findings indicate that connectivity profiles of functional and structural brain networks might act as organizing principles behind age-related cortical thinning as an imaging surrogate of cortical atrophy.

neuroscience↗

bioRxiv2022

The uncharacterized protein YgfB contributes to β-lactam resistance in Pseudomonas aeruginosa by inhibiting the expression of the amidase AmpDh3

YgfB-mediated {beta}-lactam resistance was recently identified in multi drug resistant Pseudomonas aeruginosa. We show that YgfB upregulates expression of the {beta}-lactamase AmpC by repressing the function of the regulator of the programmed cell death pathway AlpA. In response to DNA damage, the antiterminator AlpA induces expression of the alpBCDE autolysis genes and of the peptidoglycan amidase AmpDh3. YgfB interacts with AlpA and represses the ampDh3 expression. Thus, YgfB indirectly prevents AmpDh3 from reducing the levels of cell wall-derived 1,6-anhydro-N-acetylmuramyl-peptides, required to induce the transcriptional activator AmpR in promoting the ampC expression and {beta}-lactam resistance. Ciprofloxacin-mediated DNA damage induces AlpA-dependent production of AmpDh3 as previously shown, which should reduce {beta}-lactam resistance. YgfB, however, counteracts the {beta}-lactam enhancing activity of ciprofloxacin by repressing ampDh3 expression and lowering the benefits of this drug combination. Altogether, YgfB represents a new player in the complex regulatory network of AmpC regulation.

microbiology↗

bioRxiv2022

CeGAL: revisiting a widespread fungal-specific TF family using an in silico error-aware approach to identify missing zinc cluster domains

Transcription factors (TF) regulate gene activity in eukaryotic cells by binding specific regions of genomic DNA. In fungi, the most abundant TF class contains a fungal-specific GAL4-like Zn2C6 DNA binding domain (DBD), while the second class contains another fungal-specific domain, known as fungal_trans or Middle Homology Domain (MHD), whose function remains largely uncharacterized. Remarkably, almost a third of MHD-containing TF in public sequence databases apparently lack DNA binding activity, since they are not predicted to contain a DBD. Here, we reassess the domain organization of these MHD-only proteins using an in silico error-aware approach. Our large-scale analysis of ~17000 MHD-only TF sequences showed that the vast majority (>90%) result from gene annotation errors, thus contradicting previous findings that the MHD-only TF are widespread in fungi. We show that they are in fact exceptional cases, and that the Zn2C6-MHD domain pair represents the canonical domain signature defining a new TF family composed of two fungal-specific domains. We call this family CeGAL, after the most characterized members: Cep3, whose 3D structure has been determined and GAL4, an archetypal eukaryotic TF. This definition should improve the classification of the Zn2C6 TF and provide critical insights into fungal gene regulatory networks. IMPORTANCEIn fungi, extensive efforts focus on genome-wide characterization of potential Transcription Factors (TFs) and their targets genes to provide a better understanding of fungal processes and a rational for transcriptional manipulation. The second most abundant families of fungal-specific TFs, characterized by a Middle Homology Domain, are major regulators of primary and secondary metabolisms, multidrug resistance and virulence. Remarkably, one third of these TFs do not have a DNA Binding Domain (DBD-orphan) and thus are excluded from genome-wide studies. This particularity has been the subject of debate for many years. By computationally inspecting the close genomic environment of about 20,000 DBD-orphan TFs from a wide range of fungal species, we reveal that more than 90% contained sequences encoding a zinc-finger DBD. This analysis implies that the arrays of DBD containing TFs and their control DNA-sequences in target genes need to be reconsidered and expands the combinatorial regulation degree of the crucial fungal processes controlled by this TF family.

bioinformatics↗

bioRxiv2022

Control of NK cell tolerance in MHC class I-deficiency by regulated SHP-1 localization to the activating immune synapse

Signaling via inhibitory KIR/Ly49 receptors preserves natural killer (NK) cell self-tolerance but also conveys NK cell reactivity towards MHC class-I low target cells in an education process. Here, we demonstrate that mouse NK cell education by H-2Dd regulates transcription of several genes in Ly49A+ NK cells including Ptpn6, encoding the phosphatase SHP-1. SHP-1 was highly expressed in uneducated NK cells, in which knock-out of Ptpn6 increased responsiveness. Following NKp46 triggering of uneducated NK cells, a higher synaptic abundance of phosphorylated SHP-1 was found relative to educated NK cells, concomitant with reduced phosphorylation of several signaling molecules, including PLC-g2, SLP-76, ZAP70/Syk and ERK1/2. SHP-1 overlapped extensively with F-actin and SLP-76 in the uneducated activating synapse of Ly49A+ NK cells, whereas a greater association between Ly49A and SHP-1 was observed in educated NK cells. Thus, our results indicate that in addition to transcriptional regulation, a distinct SHP-1 patterning in NK cell activating synapses can determine their tolerance.

immunology↗

bioRxiv2022

Delimiting Continuity: Comparison of Target Enrichment and ddRAD for Delineating Admixing Parapatric Melitaea Butterflies

Parapatrically distributed taxa pose a challenge for species delimitation due to the presence of gene flow and inherent arbitrariness of exactly defining the species boundaries in such systems. We tackled the problem of species delimitation in a parapatric species pair of Melitaea butterflies using two popular genomic methods - double digest restriction-site associated DNA sequencing (ddRAD) and target enrichment. The former is mainly applied at shallow phylogenetic scales and the latter at both deep and shallow scales. Although both of these methods have been adequately utilised for species delimitation purposes, there are only a handful of studies that have compared these two genomic approaches in the same study system. We applied phylogenetic, population genetic and species delimitation methods and compared the results obtained from the two approaches. Using a recently developed target enrichment probe kit, we were able to capture 1,743 loci with a low amount of missing data and compared these with already available ddRAD data from a previous study on the same set of specimens. We recovered consistent phylogenetic relationships across the datasets, both demonstrating the presence of a genetically distinct Balkan lineage and paraphyly of Melitaea athalia with respect to Melitaea celadussa. The same relationships were also found in a species tree analysis of the target enrichment dataset using ASTRAL. Population genetic STRUCTURE analyses supported the presence of two species when using ddRAD data, but three species when using target enrichment, while the Bayes factor delimitation analysis found both two and three species scenarios equally decisive in both datasets. From the geographic distribution of genomic admixture, we confirm the patterns observed by a previous study that used ddRAD data. As the results obtained from both methods were largely congruent, we discuss some practical considerations and benefits of target enrichment over RAD sequencing. We conclude that the choice of method of genomic data collection does not influence the results of phylogenetic analyses at alpha taxonomic level, given a sufficient number of loci. Finally, we recommend a solution for delineating species in parapatric scenarios by proposing that parapatric taxa be consistently classified as subspecies or complete species, but not both, to promote taxonomic stability.

evolutionary biology↗