Biology subjects

Faber, F.

Publications and source records attributed to Faber, F..

10 recordsLinked to original sources

bioRxiv2026

A primary human muscle cell-based assay for detecting myasthenia gravis autoantibody binding and assessing AChR cluster impairment

Myasthenia gravis (MG) is an autoimmune disease caused by pathogenic autoantibodies against proteins at the neuromuscular junction (NMJ). The diagnosis and clinical management of MG patients largely relies on the detection of antigen-specific autoantibodies targeting acetylcholine receptor (AChR) or muscle-specific kinase (MuSK). Yet a subset of patients remains seronegative for known MG autoantibodies, highlighting a critical need for alternative approaches to identify pathogenic NMJ antibodies. We established a new human in vitro model of the NMJ based on primary human muscle cells that recapitulates key features of the NMJ: differentiation to myotubes, expression of key NMJ proteins and formation of postsynaptic AChR clusters in response to agrin stimulation. The model allows new insights into myogenesis and genetic muscle diseases, and the new muscle cell-based assay (CBA) detected autoantibodies in sera from patients with AChR- and MuSK-positive MG with 96.43% sensitivity and 100% specificity, while healthy control sera showed no reactivity. Incubation with patient sera significantly reduced AChR clustering compared to controls, demonstrating functional pathogenic effects. Thus, we established a physiologically relevant human NMJ model that enables detection and functional characterization of neuromuscular autoantibodies. This novel approach addresses a key limitation of current antigen-specific diagnostics and provides a method for improved detection and characterization of MG antibodies, independent of antigen specificity. One Sentence SummaryWe established a postsynaptic human in vitro neuromuscular junction model to assess binding and pathogenicity of MG autoantibodies. Key messagesO_ST_ABSWhat is already known on this topic?C_ST_ABSCurrent diagnosis of myasthenia gravis (MG) relies largely on the detection of antigen-specific autoantibodies against AChR and MuSK, leaving a clinically relevant subset of patients seronegative. What are the new findings?We established a physiologically relevant human in vitro neuromuscular junction model based on primary human muscle cells and developed a novel muscle cell-based assay (CBA) for the detection of neuromuscular autoantibodies. How might this impact on clinical practice or future developments?The CBA detected autoantibodies in patients with AChR- or MuSK-positive MG with high sensitivity and specificity and demonstrated their functional pathogenic effects on AChR clustering. This antigen-independent approach may improve the detection and functional characterization of MG autoantibodies, particularly in patients who are seronegative in current diagnostic assays. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/743478v1_ufig1.gif" ALT="Figure 1000"> View larger version (38K): org.highwire.dtl.DTLVardef@c2e1fforg.highwire.dtl.DTLVardef@8336fforg.highwire.dtl.DTLVardef@8fa2b0org.highwire.dtl.DTLVardef@1d94e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Epigenetic dysregulation of Th2 cytokine genes in MuSK myasthenia gravis and its modulation by immunosuppressive therapy

Background and objectivesMyasthenia gravis associated with antibodies against muscle-specific kinase (MuSK-MG) is a well-characterized IgG4-autoimmune disease, however, the mechanisms driving IgG4 predominance remain poorly understood. This study investigated whether promoter DNA methylation of cytokine genes involved in IgG4 class switching is associated with this immune response. MethodsPeripheral blood mononuclear cells were isolated from MuSK-MG patients (n=36), acetylcholine receptor myasthenia gravis (AChR-MG) patients as disease controls (n=7), and sex-matched healthy controls (n=12). Promoter DNA methylation of IL4, IL10, and IL13 was assessed by methylation-sensitive high-resolution melting and relative cytokine mRNA expression by qPCR. Associations with clinical variables, and antibody levels were subsequently evaluated. ResultsMuSK-MG patients showed lower median IL13 promoter methylation compared with healthy controls (p = 0.004). Median IL4 promoter methylation was also reduced in MuSK-MG compared with healthy controls (p < 0.001) and AChR-MG disease controls (p < 0.001), whereas no differences were observed for IL10 promoter methylation. Relative mRNA expression of IL4 (p = 0.0005), IL10 (p = 0.0462), and IL13 (p = 0.0002) was increased in MuSK-MG compared with AChR-MG. Compared with healthy controls, only IL4 expression remained significantly increased (p < 0.0001). Promoter methylation was inversely correlated with relative mRNA expression for IL4 (p < 0.0001), while IL13 showed a similar but non-significant trend (p = 0.054), no association was observed for IL10. Multivariable analysis demonstrated that treatment at sampling was independently associated with lower IL10 and IL13 promoter methylation, whereas no associations were observed with age, sex, disease phase, or disease duration. Promoter methylation did not correlate with total serum IgG4 or anti-MuSK IgG4 levels. DiscussionMuSK-MG is associated with selective hypomethylation of IL4 and IL13 promoters accompanied by increased cytokine gene expression, while IL10 promoter methylation remains unchanged. The association between treatment and IL10 and IL13 promoter methylation suggests that immunosuppressive therapy may influence epigenetic regulation in MuSK-MG. Together, these findings support a role for epigenetic dysregulation of Th2-associated cytokines in the immunological environment associated with IgG4 subclass switch. To our knowledge, this is the first study investigating IL4, IL10, and IL13 promoter DNA methylation in MuSK-MG.

immunology↗

bioRxiv2026

ASO-mediated mRNA silencing enables functional analysis and selective depletion of the human microbiota Prevotellaceae

The Prevotellaceae family comprises abundant, taxonomically diverse bacteria of the human microbiota that exhibit remarkable intraspecies variability and distinct phenotypes during host-microbe interactions. Yet functional investigations are hampered by the limited genetic tractability of this medically important bacterial family, rendering it understudied. Here, we apply antisense oligomer (ASO) technology to selectively inhibit translation of single or multiple mRNAs across nine Prevotellaceae species. Using ftsZ- and mreB-related phenotypes as morphogenic readouts, we demonstrate that ASOs can function as a tunable system to study essential gene function. Further, we show that ASOs can selectively deplete target species from a synthetic Bacteroidales community. These results establish ASOs as practical tools for functional genomics and community modulation in otherwise genetically intractable anaerobic microbiota members.

microbiology↗

bioRxiv2025

A novel two-component system controls vancomycin resistance in epidemic Clostridioides difficile

The glycopeptide antibiotic vancomycin is the frontline treatment for C. difficile infection in the UK. There have been only sporadic reports of resistance in the clinic but testing is rare so the true resistance landscape is unclear. We have previously shown that resistance can emerge rapidly in vitro via distinct but complementary pathways. Strain Bc2, characterised here, is an experimentally evolved derivative of C. difficile strain R20291 that displays a 16-fold increase in vancomycin MIC over its parent. Bc2 has point mutations in dacS, bclA3, CDR20291_0794, CDR20291_1871 and CDR20291_3124 (vnrS). By genetically engineering a wild-type vancomycin susceptible strain, we demonstrated that a combination of just two mutations, dacSc.798A>T and vnrSc.692G>T, both of which encode two-component system histidine kinases, was sufficient to recapitulate Bc2 resistance. We have previously shown that mutations in dacS can confer low level resistance via increases in the expression of a D,D-carboxypeptidase DacJ. dacSc.798A>T also led to increased transcription of dacJ and led to a modest increase in vancomycin MIC. Surprisingly vnrSc.692G>T led to overexpression of the vanG cluster, which encodes all of the enzymes needed for resistance via substitution of the terminal D-Ala on peptidoglycan lipid II precursors with D-Ser. Genomic analysis of a large collection of European C. difficile strains showed that a three gene cluster, which includes vnrS, vnrR (encoding the cognate response regulator) and an adjacent gene CDR20291_3123, is unique to the phylogenetic branch that contains strains belonging to epidemic ribotypes 027 and 176. Transcriptomic analysis of the wider VnrS regulon also revealed an additional previously unknown role in regulating the expression of the flagellum, an important virulence factor in C. difficile. Analysis of the response to vancomycin exposure also revealed that dacJ is one of a small set of genes that are upregulated shortly after antibiotic stress, even in the absence of mutations that typically lead to its overexpression. Together these data reveal a new synergistic route, needing only two point mutations, by which epidemic lineages of C. difficile can attain vancomycin resistance. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=147 HEIGHT=200 SRC="FIGDIR/small/671617v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@bba369org.highwire.dtl.DTLVardef@e562acorg.highwire.dtl.DTLVardef@1b112deorg.highwire.dtl.DTLVardef@4dcf8a_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

Proton-pump inhibitors increase C. difficile infection risk by altering pH rather than by affecting the gut microbiome based on a bioreactor model

Clostridioides difficile infections often occur after antibiotic use, but they have also been linked to proton-pump inhibitor (PPI) therapy. The underlying mechanism--whether infection risk is due to a direct effect of PPIs on the gut microbiome or changes in gastrointestinal pH--has remained unclear. To disentangle both possibilities, we studied the impact of the proton-pump inhibitor omeprazole and pH changes on key members of the human gut microbiome and stool-derived microbial communities from different donors in vitro. We then developed a custom multiple-bioreactor system to grow a model human microbiome community in chemostat mode and tested the effects of omeprazole exposure, pH changes, and their combination on C. difficile growth within this community. Our findings show that changes in pH significantly affect the gut microbial communitys biomass and the abundances of different strains, leading to increased C. difficile growth within the community. However, omeprazole treatment alone did not result in such effects. These findings imply that the higher risk of C. difficile infection following proton-pump inhibitor therapy is probably because of alterations in gastrointestinal pH rather than a direct interaction between the drug and the microbiome. This understanding paves the way for reducing infection risks in proton-pump inhibitor therapy.

microbiology↗

bioRxiv2023

The RNA-binding protein RbpB is a central regulator of polysaccharide utilization in gut Bacteroides

Paramount to human health, symbiotic bacteria in the gastrointestinal tract rely on the breakdown of complex polysaccharides to thrive in this sugar-deprived environment. Gut Bacteroides are metabolic generalists and deploy dozens of polysaccharide utilization loci (PULs) to forage diverse dietary and host-derived glycans. The expression of the multi-protein PUL complexes is tightly regulated at the transcriptional level. However, how PULs are orchestrated at translational level in response to the fluctuating levels of their cognate substrates is unknown. Here, we identify the RNA-binding protein RbpB and a family of noncoding RNAs as key players in post-transcriptional PUL regulation. Ablation of RbpB in Bacteroides thetaiotaomicron displays compromised colonization in the mouse gut in a host diet-dependent manner. Current dogma holds that individual PULs are regulated by dedicated transcriptional regulators. We demonstrate that RbpB acts as a global RNA binder that directly interacts with several hundred cellular transcripts. This includes a paralogous noncoding RNA family comprised of 14 members, the FopS (family of paralogous sRNAs) cluster. Through a series of in-vitro and in-vivo assays, we reveal that FopS sRNAs repress the translation of a SusC-like glycan transporter when substrates are limited--an effect antagonized by RbpB. Together, this study implicates RNA-coordinated metabolic control as an important, yet previously overlooked, factor contributing to the in-vivo fitness of predominant microbiota species in dynamic nutrient landscapes.

microbiology↗

bioRxiv2023

Formation of the pyruvoyl-dependent proline reductase Prd from Clostridioides difficile requires the maturation enzyme PrdH

Stickland fermentation, the coupled oxidation and reduction of amino acid pairs, is a major pathway for obtaining energy in the nosocomial bacterium Clostridioides difficile. D-proline is the preferred substrate for the reductive path, making it not only a key component of the general metabolism but also impacting on the expression of the clostridial toxins TcdA and TcdB. D-proline reduction is catalyzed by the proline reductase Prd, which belongs to the pyruvoyl-dependent enzymes. These enzymes are translated as inactive proenzymes and require subsequent processing to install the covalently bound pyruvate. Whereas pyruvoyl formation by intramolecular serinolysis has been studied in unrelated enzymes, details about pyruvoyl generation by cysteinolysis such as in Prd are lacking. Here we show that Prd maturation requires a small dimeric protein that we have named PrdH. PrdH is co-encoded with the PrdA and PrdB subunits of Prd and also found in species producing similar reductases. By producing stable variants of PrdA and PrdB, we demonstrate that PrdH-mediated cleavage and pyruvoyl formation in the PrdA subunit require PrdB, which can be harnessed to produce active recombinant Prd for subsequent analyses. We further created PrdA- and PrdH-mutants to get insight into the interaction of the components and into the processing reaction itself. Finally, we show that deletion of prdH in C. difficile renders the corresponding mutant blind to proline, suggesting that this processing factor is essential for proline utilization. Due to the link between Stickland fermentation and pathogenesis, we suggest PrdH may be an attractive target for drug development. Significance StatementEnergy conservation via Stickland fermentation was first described in the 1930s, yet information about the key enzyme of this process, Prd, is scarce, despite the fact that its central role in both metabolism and toxin production make it a promising potential drug target. Here we show how a small, previously overlooked protein that we named PrdH mediates the formation of the catalytically essential pyruvoyl-group in the active center of Prd. In vivo studies in C. difficile emphasize its critical importance in the utilization of proline. The known interplay between proline reduction and toxin production leads us to suggest PrdH as a potential drug target. Moreover, our findings open the door for further structural and functional studies with recombinantly produced active Prd.

biochemistry↗

bioRxiv2023

Byproducts of inflammatory radical metabolism provide transient nutrient niches for microbes in the inflamed gut

Louis Pasteurs experiments on tartaric acid laid the foundation for our understanding of molecular chirality, but major questions remain. By comparing the optical activity of naturally-occurring tartaric acid with chemically-synthesized paratartaric acid, Pasteur realized that naturally-occurring tartaric acid contained only L-tartaric acid while paratartaric acid consisted of a racemic mixture of D- and L-tartaric acid. Curiously, D-tartaric acid has no known natural source, yet several gut bacteria specifically degrade D-tartaric acid. Here, we investigated the oxidation of monosaccharides by inflammatory reactive oxygen and nitrogen species. We found that this reaction yields an array of alpha hydroxy carboxylic acids, including tartaric acid isomers. Utilization of inflammation- derived D- and L-tartaric acid enhanced colonization by Salmonella Typhimurium and E. coli in murine models of gut inflammation. Our findings suggest that byproducts of inflammatory radical metabolism, such as tartrate and other alpha hydroxy carboxylic acids, create transient nutrient niches for enteric pathogens and other potentially harmful bacteria. Furthermore, this work illustrates that inflammatory radicals generate a zoo of molecules, some of which may erroneously presumed to be xenobiotics.

microbiology↗

bioRxiv2022

A network of small RNAs regulates sporulation initiation in C. difficile

The obligate anaerobic, enteric pathogen Clostridioides difficile persists in the intestinal tract by forming antibiotic resistant endospores that contribute to relapsing and recurrent infections. Despite the importance of sporulation for C. difficile pathogenesis, environmental cues, and molecular mechanisms regulating sporulation initiation remain ill defined. Here, using RIL-seq to capture the Hfq-dependent RNA-RNA interactome, we discovered a network of small RNAs that bind to mRNAs encoding sporulation-related genes. We show that two of these small RNAs, SpoX and SpoY, regulate translation of the master regulator of sporulation, Spo0A, in an opposing manner, which ultimately leads to altered sporulation rates. Infection of antibiotic-treated mice with SpoX and SpoY deletion mutants revealed a global effect on gut colonization and intestinal sporulation. Our work uncovers an elaborate RNA-RNA interactome controlling the physiology and virulence of C. difficile and identifies a complex post-transcriptional layer in the regulation of spore formation in this important human pathogen.

molecular biology↗

bioRxiv2020

An RNA-centric global view of Clostridioides difficile reveals broad activity of Hfq in a clinically important Gram-positive bacterium

The Gram-positive human pathogen Clostridioides difficile has emerged as the leading cause of antibiotic-associated diarrhea. Despite growing evidence for a role of Hfq in RNA-based gene regulation in C. difficile, little is known about the bacteriums transcriptome architecture and mechanisms of post-transcriptional control. Here, we have applied a suite of RNA-centric techniques, including transcription start site mapping, transcription termination mapping and Hfq RIP-seq, to generate a single-nucleotide resolution RNA map of C. difficile 630. Our transcriptome annotation provides information about 5 and 3 untranslated regions, operon structures and non-coding regulators, including 42 sRNAs. These transcriptome data are accessible via an open-access browser called Clost-Base. Our results indicate functionality of many conserved riboswitches and predict novel cis-regulatory elements upstream of MDR-type ABC transporters and transcriptional regulators. Recent studies have revealed a role of sRNA-based regulation in several Gram-positive bacteria but their involvement with the RNA-binding protein Hfq remains controversial. Here, sequencing the RNA ligands of Hfq reveals in vivo association of many sRNAs along with hundreds of potential target mRNAs in C. difficile providing evidence for a global role of Hfq in post-transcriptional regulation in a Gram-positive bacterium. Through integration of Hfq-bound transcripts and computational approaches we predict regulated target mRNAs for the novel sRNA AtcS encoding several adhesins and the conserved oligopeptide transporter oppB that influences sporulation initiation in C. difficile. Overall, these findings provide a potential mechanistic explanation for increased biofilm formation and sporulation in an hfq deletion strain and lay the foundation for understanding clostridial ribo regulation with implications for the infection process.

microbiology↗