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Biology subjects

Mayer, G.

Publications and source records attributed to Mayer, G..

At least 19 recordsLinked to original sources

Daily locomotor rhythms and ecdysial stage-dependent behaviors in the tardigrade Hypsibius exemplaris

Tardigrades, key ecdysozoan organisms, have poorly characterized daily behavioral rhythms linked to their molting (ecdysial) cycle. We continuously tracked the locomotor activity of the model tardigrade Hypsibius exemplaris using infrared videography and deep learning-based automated tracking under three photic regimes: a light/dark cycle, constant darkness following entrainment, and constant darkness without prior entrainment. We identified a robust endogenous circadian-like rhythm in locomotor activity that persisted in constant darkness, independent of photic input. Although the light/dark cycle enhanced the rhythm amplitude and the overall animal activity, it was not required for rhythmicity. Individual phases varied widely, indicating a lack of population-level synchronization. Furthermore, we developed a behavioral classification system based on activity level, which enables categorizing distinct behaviors. Behavioral patterns were modulated by distinct ecdysial stages, with quiescence gating premolt and time-of-day dependent patterns in feeding and wandering. These findings provide evidence consistent with an endogenous, circadian-like timing system in tardigrades that integrates daily activity with molting cycles and establish H. exemplaris as a promising model for studying ecdysozoan chronobiology.

animal behavior and cognition↗

Extensive opsin gene expansion and non-cerebral origin of the minimalist eye in a model tardigrade

Panarthropod vision exhibits extraordinary morphological and functional diversity, yet the sensory biology of tardigrades--microscopic extremophiles renowned for their resilience--remains poorly understood. In the model tardigrade Hypsibius exemplaris, we uncover an unprecedented expansion of opsin genes, with over 100 paralogs constituting the largest known opsin repertoire in any animal. Paradoxically, the visual system is structurally minimalist: a paired, inverse pigment-cup ocellus embedded within the brain lobes, forming a single-pixel, dual-receptor organ. Integrating genomic, phylogenetic, molecular expression, and ultrastructural analyses, we show that directional vision relies on a single rhabdomeric opsin (He-R-Opsin-V), localized to microvilli of the rhabdomeric cell. A ciliary photoreceptor with a lamellated cilium co-expresses two ciliary opsins (He-C-Opsin-1 and -2), suggesting non-visual light detection. These and other non-visual opsins are differentially expressed in the brain, gut, storage cells, and peripheral tissues, implicating them in circadian regulation, neuromodulation, ecdysis, digestion, and environmental sensing. Crucially, the eye is an internalized epidermal vesicle, not a cerebral derivative, challenging long-standing assumptions about its evolutionary origin. These findings reveal how extreme miniaturization drives sensory system simplification in visual organs while enabling parallel evolutionary innovation in non-visual photoreception. This study establishes a new paradigm for sensory evolution in microscale animals.

zoology↗

The ancient metazoan cytoplasmic intermediate filament protein, Cilin, shapes cilia arrangement and tissue architecture

The emergence of animal multicellularity demanded novel cytoskeletal systems to support cellular architecture and tissue integrity. Cytoplasmic intermediate filaments (cIFs) are essential components of this scaffold, yet their evolutionary origins remain obscure. Here, we identify and characterize a lamin-derived, bona fide cIF protein in a ctenophore--a sister lineage to all other extant animals. We name this protein Cilin. Unlike nuclear lamins, Cilin lacks a nuclear localization signal and instead localizes predominantly to motile ciliary structures, including comb plates, the aboral organ, and sperm flagella, indicating a central role in ciliary architecture and function. Remarkably, Cilin is also present in non-ciliated cells, suggesting early functional diversification of cIFs in animal evolution. Phylogenetic and structural analyses position Cilin within an ancestral class of intermediate filament proteins, homologous to cnidarian and bilaterian nematocilins and lamin-tail-domain-containing (LMNTD) proteins. In humans, LMNTD proteins are enriched in ciliated epithelia and spermatids, pointing to a deeply conserved role in cilia-associated functions. These findings establish cilins as the earliest lamin-derived cytoplasmic intermediate filament proteins in metazoans, likely contributing to both ciliary function and the emergence of multicellular tissue organization.

cell biology↗

Receptor-based protein binding in the supramolecular network of velvet worm slime

The slime of velvet worms (Onychophora) is a protein-based bioadhesive that undergoes rapid, yet reversible transition from a fluid into stiff fibers used for prey capture and defense, but the mechanism by which this phase transition functions is largely unknown. Here, integrating transcriptomic and proteomic approaches with AI-guided structure predictions, we discover a group of evolutionarily conserved leucine-rich repeat (LRR) proteins in velvet worm slime that readily adopt a receptor-like, protein-binding "horseshoe" structure. Our structural predictions suggest dimerization of LRR proteins and support their interactions with conserved {beta}-sheets-rich domains of high-molecular-weight proteins, the primary building blocks of velvet worm slime fibers. This previously unknown functional context of LRR proteins is presumably involved in reversible, receptor-based supramolecular network formation in these adhesive biofibers and provides possible new avenues for fabricating fully recyclable (bio)polymeric materials. Significance StatementAnalyzing structure-function-relationships underlying reversible fiber formation in velvet worm slime may inspire avenues for the sustainable fabrication of protein-based polymeric materials. Here, we present evidence for an evolutionarily conserved mechanism of reversible fiber formation in velvet worm slime based on the receptor-like binding of fiber forming proteins by a leucine-rich repeat (LRR) protein. The structures of both protein components are highly conserved evolutionarily in the two distantly related velvet worm subgroups, indicating pervasive presence of this mechanism across species that has been maintained through the last [~]380 MY. Our results suggest that the ubiquitously occurring LRR motif--better known for its innate immunity and developmental roles--has a novel identified function in processing a biological material, which might contribute to the development of sustainable bio-inspired materials.

biochemistry↗

FibrilPaint targets amyloid fibrils for ubiquitination

Failure of the Protein Quality Control (PQC) System to control the Tau protein leads to amyloid fibrils that are at the basis of various Tauopathies, including Alzheimers Disease (AD). Reinstating the PQC for Tau is desirable. Here we show that the PROTAC peptide FibrilPaint20 (FP20) recruits the ubiquitination system to Tau amyloid fibrils. We reconstituted the ubiquitin-proteasome cascade and monitored the stepwise ubiquitin transfer using the microfluidics technique FIDA. To direct ubiquitination specifically to amyloids, we discovered FP20, a bifunctional peptide that connects amyloid fibrils to the E3 ligase CHIP. FP20 mediated ubiquitination of recombinant and patient derived fibrils from various tauopathies, ultimately enabling the 26S proteasome to target CHIP-ubiquitinated Tau fibrils. This shows that FP20 cooperates with the PQC system and can initiate fibril cleavage. This offers a strategy to target amyloid diseases by cooperation with the PQC system exploiting key cellular systems.

biochemistry↗

Fibril Paint: a class of amyloid-targeting peptides

Amyloid fibrils are a common pathological hallmark in multiple neurodegenerative diseases, yet molecular tools to selectively recognise and manipulate them remain scarce. We report FibrilPaints, a family of modular peptides designed for selective amyloid binding and adaptable chemical functionality. The degenerative amyloid-targeting unit of FibrilPaints, W5P4H3R2, has a high content of {pi}-stacking and aromatic side chains. Systematic sequence variation, altering charge, termini, and residue order, revealed the importance of the composition of the amyloid-targeting unit for high-affinity binding across Tau and Huntingtin fibrils. Importantly, sequence changes outside this unit do not preclude fibril binding, which permits attachment of fluorophores or E3-recruiting motifs for targeted protein degradation. This work establishes FibrilPaint as a modular peptide system for the detection and modulation of amyloids. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/609586v4_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1e9cadborg.highwire.dtl.DTLVardef@50f9eorg.highwire.dtl.DTLVardef@446ee8org.highwire.dtl.DTLVardef@cd47a2_HPS_FORMAT_FIGEXP M_FIG Figure of content The modular design of FibrilPaints enables systematic evaluation of their functionality by testing the binding capacity of each variant (FibrilPaintX) to distinct amyloid fibrils. Successful binding results in visible painting of the fibrils, facilitating their detection and downstream research. C_FIG

biochemistry↗

Pigment-dispersing factor neuropeptides act as multifunctional hormones and modulators in tardigrades

Pigment-dispersing factors (PDFs) are neuropeptides that play key roles in controlling the circadian rhythms in various insects, whereas their function remains elusive in other protostomes including tardigrades (water bears). Here we show that the three PDFs of the tardigrade Hypsibius exemplaris are co-localized in two pairs of inner lobe cells in the brain, whereas only one PDF occurs in four additional cerebral and two extracerebral cells. The axons of the inner lobe cells pass through the contralateral brain hemisphere, descend to the ventral nerve cord and terminate in two pairs of potential release sites in the posteriormost trunk ganglion. Using in vitro assays, we demonstrate that all three PDFs and their deorphanized receptor (PDFR) are functional. Widespread localization of PDFR suggests that tardigrade PDFs may act as multifunctional hormones and neuromodulators that control major functions including light detection, neural processing, locomotion, feeding, digestion, osmoregulation, growth, embryonic development, and oogenesis/reproduction.

zoology↗

Early IKKb-dependent anabolic signature governs vascular smooth muscle cells fate and abdominal aortic aneurysm development

BackgroundAbdominal aortic aneurysm (AAA) is a detrimental disease with no effective pharmacological therapy. While inflammation is recognized as one of the key regulators of AAA, targeting inflammatory pathways once the disease is established does not impact the outcomes. However, understanding the earliest molecular indicators could shed light on the precise biological targets and prognostic markers for AAA. MethodsUsing apolipoprotein E (ApoE)-deficient mice fed with a standard diet and infused with Angiotensin II (Ang II), we conducted bulk RNA-sequencing (RNA-Seq) analysis on suprarenal (SRA) regions obtained from both unchallenged and challenged WT mice, specifically examining responses 24 hours after Ang II infusion to capture the initial phases of aortic stress response. We further created a unique model of hyperlipidemic mice in which the expression of the inhibitor of nuclear factor kappa B kinase subunit beta (IKK{beta}) can be conditionally (via tamoxifen injection) suppressed in vascular smooth muscle cells (VSMC). The development of AAA was evaluated using in situ examination and quantified using RT-qPCR, immunohistochemistry and fluorescence microscopy. Cultured VSMC were exposed to the selective IKK{beta} inhibitor MLN120b and the expression levels of phenotypic markers kruppel like factor 4 (KLF4), {beta}-Catenin and cellular communication network factor 2 (CCN2) were addressed using cellular extracts and immunoblot analysis. ResultsRNA-Seq data support the presence of early anabolic events in SRA regions detailing activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway, which paralleled cellular anabolic processes including mitochondria, ribosome and sterol biosynthesis, the Unfolded Protein Response (UPR) and fibrogenesis. Conditional deletion of the Ikbkb gene in VSMC significantly reduces the incidence of SRA lesions as well as the rate of aneurysm ruptures in mice exposed to Ang II. In situ analysis further demonstrated that the protection conferred by the lack of IKK{beta} expression in VSMC is associated with reduced inflammatory response, the preservation of the contractile over the degradative VSMC phenotypes, and the absence of an anabolic signature. ConclusionOur results not only reinforce the major roles played by VSMC in the rapid adaptation leading to the deleterious remodeling of the vascular wall and aortic lesions but also support a paradigm aiming at repositioning the efforts focusing on anabolic rather than inflammatory events.

molecular biology↗

Binding of SARS-CoV-2 nucleocapsid protein to uninfected epithelial cells induces antibody-mediated complement deposition

SARS-CoV-2 infection triggers strong antibody response toward Nucleocapsid-Protein (NP), suggesting extracellular presence beyond its intra-virion RNA binding. Interestingly, NP was found to decorate infected and proximal uninfected cell-surfaces. Here, we propose a new mechanism through which extracellular NP on uninfected cells contributes to COVID-19 pathogenicity. We show that NP binds to cell-surface sulfated linear-glycosaminoglycans by spatial rearrangement of its RNA-binding sites facilitated by the flexible, positively charged, linker. Coating of uninfected lung-derived cells with purified NP attracted anti-NP-IgG from lung fluids and sera collected from COVID-19 patients. The magnitude of this immune recognition was significantly elevated in moderate compared to mild COVID-19 cases. Importantly, binding of anti-NP-IgG present in sera generated clusters that triggered C3b deposition by the classical complement pathway. Heparin analog enoxaparin outcompeted NP-binding, rescuing cells from anti-NP IgG-mediated complement deposition. Our findings unveil how extracellular NP may exacerbate COVID-19 tissue damage, and suggest leads for preventative therapy. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/585388v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1084e20org.highwire.dtl.DTLVardef@4126caorg.highwire.dtl.DTLVardef@159c610org.highwire.dtl.DTLVardef@da7b7f_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIgG from patients sera target NP-bound cells resulting in complement activation C_LIO_LIThe flexible linker allows NP to both bind linear sulfated GAGs and wrap around RNA C_LIO_LIHeparin analogs prevent NP surface binding and alleviate complement activation C_LIO_LICell-ELISA anti-NP IgG levels differ between mild and moderate COVID-19 C_LI

immunology↗

Fibril Paint to detect Amyloids and determine Fibril Length

Tau aggregation into amyloid fibrils is linked to the development of neurodegenerative diseases, including Alzheimers Disease. The molecular processes underlying aggregation in disease are poorly understood. Here, we introduce FibrilPaint1 as a tool to measure the size of Tau amyloid fibrils in fluids, from early aggregation stages to mature fibrils. FibrilPaint1 is a 22mer peptide with many exciting properties, which makes it a tool for diagnostics and an attractive start point for developing a class of effective fibril targeting degraders: (i) FibrilPaint1 binds fibrils with nanomolar affinity; (ii) it does also bind to oligomeric precursors, down to a size of only 4 layers; (iii) it does not bind to monomers (KD > 100 {micro}M); (iv) it is fluorescently labelled, which allows monitoring and localising interactions. (v) FibrilPaint1 recognises various Tau fibrils, including patient derived fibrils from Alzheimer, Corticobasal degeneration and Frontotemporal dementia; (vi) FibrilPaint1 is selective for the amyloid state and does not have background binding to amorphous aggregates, blood serum or cell lysate. In combination with Flow Induced Dispersion Analysis (FIDA), a microfluidics technology, we determined the molecular size of amyloid fibrils with sub-microliter sample volumes. This set-up acts as a molecular ruler at layer resolution - we determined Tau fibril length from 4 to 1100 layers in solution. This is an interesting parameter that can be used for diagnostic applications and biochemical research in dementia.

biochemistry↗

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↗

A peptide strategy for inhibiting different protein aggregation pathways in disease

Protein aggregation correlates with many human diseases. Protein aggregates differ in shape, ranging from amorphous aggregates to amyloid fibrils. Possibly for such heterogeneity, strategies to develop effective aggregation inhibitors that reach the clinic failed so far. Here, we present a new strategy by which we developed a family of peptides targeting early aggregation stages for both amorphous and fibrillar aggregates of proteins unrelated in sequence and structure. Thus, they act on dynamic precursors before a mechanistic differentiation takes place. Using a peptide array approach, we first identified peptides inhibiting the predominantly amorphous aggregation of a molten globular, aggregation-prone protein, a thermolabile mutant of the Axin tumor suppressor. A series of optimization steps revealed that the peptides activity did not depend on their sequences but rather on their molecular determinants. The key properties that made a peptide active were a composition of 20-30% flexible, 30-40% aliphatic and 20-30% aromatic residues, a hydrophobicity/hydrophilicity ratio close to 1 and an even distribution of residues of different nature throughout the sequence. Remarkably, the optimized peptides also suppressed fibrillation of Tau, a disordered protein that forms amyloids in Alzheimers disease, and entirely unrelated to Axin. Our compounds thus target early aggregation stages, independent of the aggregation mechanism, inhibiting both amorphous and amyloid aggregation. Such cross-mechanistic, multi-targeting aggregation inhibitors may be attractive lead compounds against multiple protein aggregation diseases.

biochemistry↗

Light-dependent Control of Bacterial Expression at the mRNA Level

Sensory photoreceptors mediate numerous light-dependent adaptations across organisms. In optogenetics, photoreceptors achieve the reversible, non-invasive, and spatiotemporally precise control by light of gene expression and other cellular processes. The light-oxygen-voltage receptor PAL binds to small RNA aptamers with sequence specificity upon blue-light illumination. By embedding the responsive aptamer in the ribosome-binding sequence of genes of interest, their expression can be downregulated by light. We developed the pCrepusculo and pAurora optogenetic systems that are based on PAL and allow to down- and upregulate, respectively, bacterial gene expression using blue light. Both systems are realized as compact, single plasmids that exhibit stringent blue-light responses with low basal activity and up to several ten-fold dynamic range. As PAL exerts light-dependent control at the RNA level, it can be combined with other optogenetic circuits that generally control transcription initiation. By integrating regulatory mechanisms operating at the DNA and mRNA levels, optogenetic circuits with emergent properties can thus be devised. As a case in point, the pEnumbra setup permits to upregulate gene expression under moderate blue light whereas strong blue light shuts off expression again. Beyond providing novel signal-responsive expression systems for diverse applications in biotechnology and synthetic biology, our work also illustrates how the light-dependent PAL-aptamer interaction can be harnessed for the control and interrogation of RNA-based processes.

biochemistry↗

A SARS-CoV-2 spike binding DNA aptamer that inhibits pseudovirus infection in vitro by an RBD independent mechanism

The receptor binding domain (RBD) of the spike glycoprotein of the coronavirus SARS-CoV-2 (CoV2-S) binds to the human angiotensin converting enzyme 2 (ACE2) representing the initial contact point for leveraging the infection cascade. We used an automated selection process and identified an aptamer that specifically interacts with CoV2-S. The aptamer does not bind to the RBD of CoV2-S and does not block the interaction of CoV2-S with ACE2. Notwithstanding, infection studies revealed potent and specific inhibition of pseudoviral infection by the aptamer. The present study opens up new vistas in developing SARS-CoV2 infection inhibitors, independent of blocking the ACE2 interaction of the virus and harnesses aptamers as potential drug candidates and tools to disentangle hitherto inaccessible infection modalities, which is of particular interest in light of the increasing number of escape mutants that are currently being reported.

biochemistry↗

A synthetic RNA-based biosensor for fructose-1,6-bisphosphate that reports glycolytic flux

Metabolic heterogeneity, the occurrence of different metabolic phenotypes among cells, represents a key challenge in health and biotechnology. To unravel its molecular basis, tools probing metabolism of single cells are needed. While RNA devices harbor huge potential for the development of such tools, until today, it is challenging to create in vivo-functional sensors for any given metabolite. Here, we developed from scratch an RNA-based sensor for fructose-1,6-bisphosphate (FBP), a doubly phosphorylated intermediate of glycolysis. Starting from in vitro selection of an RNA aptamer and its structural analyses, we developed libraries of RNA-based regulatory devices with this aptamer and the hammerhead ribozyme as an actuator. Through FACS-seq-based high-throughput screening in yeast, we identified in vivo-functional FBP-sensing devices that generate fluorescent readout dependent on intracellular FBP concentration. As FBP reports the flux through glycolysis, the developed RNA device can be used to sense the glycolytic rate in single cells, offering unprecedented possibilities to investigate the causes of metabolic heterogeneity.

synthetic biology↗

Optoribogenetic control of regulatory RNA molecules

Short regulatory RNA molecules underpin gene expression and govern cellular state and physiology. To establish a novel layer of control over these processes, we generated chimeric regulatory RNAs that interact reversibly and light-dependently with the light-oxygen-voltage photoreceptor PAL. By harnessing this interaction, the function of micro RNAs (miRs) and short hairpin (sh) RNAs in mammalian cells can be regulated in spatiotemporally precise manner. The underlying strategy is generic and can be adapted to near-arbitrary target sequences. Owing to full genetic encodability, it establishes unprecedented optoribogenetic control of cell state and physiology. The method stands to facilitate the non-invasive, reversible and spatiotemporally resolved study of regulatory RNAs and protein function in cellular and organismal environments.

molecular biology↗

Proteomics Standards Initiative Extended FASTA Format (PEFF)

Mass spectrometry-based proteomics enables the high-throughput identification and quantification of proteins, including sequence variants and post-translational modifications (PTMs), in biological samples. However, most workflows require that such variations be included in the search space used to analyze the data, and doing so remains challenging with most analysis tools. In order to facilitate the search for known sequence variants and PTMs, the Proteomics Standards Initiative (PSI) has designed and implemented the PSI Extended FASTA Format (PEFF). PEFF is based on the very popular FASTA format but adds a uniform mechanism for encoding substantially more metadata about the sequence collection as well as individual entries, including support for encoding known sequence variants, PTMs, and proteoforms. The format is very nearly backwards compatible, and as such, existing FASTA parsers will require little or no changes to be able to read PEFF files as FASTA files, although without supporting any of the extra capabilities of PEFF. PEFF is defined by a full specification document, controlled vocabulary terms, a set of example files, software libraries, and a file validator. Popular software and resources are starting to support PEFF, including the sequence search engine Comet and the knowledge bases neXtProt and UniProtKB. Widespread implementation of PEFF is expected to further enable proteogenomics and top-down proteomics applications by providing a standardized mechanism for encoding protein sequences and their known variations. All the related documentation, including the detailed file format specification and example files, are available at http://www.psidev.info/peff.

bioinformatics↗

The Genomic Basis of Arthropod Diversity

BackgroundArthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genome evolution to be addressed, even across hyper-diverse taxa within arthropods.\n\nResultsUsing 76 whole genome sequences representing 21 orders spanning more than 500 million years of arthropod evolution, we document changes in gene and protein domain content and provide temporal and phylogenetic context for interpreting these innovations. We identify many novel gene families that arose early in the evolution of arthropods and during the diversification of insects into modern orders. We reveal unexpected variation in patterns of DNA methylation across arthropods and examples of gene family and protein domain evolution coincident with the appearance of notable phenotypic and physiological adaptations such as flight, metamorphosis, sociality and chemoperception.\n\nConclusionsThese analyses demonstrate how large-scale comparative genomics can provide broad new insights into the genotype to phenotype map and generate testable hypotheses about the evolution of animal diversity.

genomics↗