Biology subjects

Kovacs, P.

Publications and source records attributed to Kovacs, P..

13 recordsLinked to original sources

bioRxiv2026

Octopamine receptors at a glance: from expression and anatomical maps to their role in development and behavior in the Drosophila melanogaster larva

Octopamine is involved in a variety of different physiological and behavioral mecha-nisms in Drosophila melanogaster. Throughout the life cycle of the fruit fly, from the larva to the adult, octopaminergic neurons in both the central and the peripheral nerv-ous system target a multitude of neurons and even non-neuronal tissues, making it challenging to analyze individual mechanisms of octopamine function. One approach to deconstructing this complex system is to examine the postsynaptic components of signal transmission. In Drosophila, octopamine interacts with six distinct G-protein-coupled receptors. For some of these receptors, expression maps and functional im-plications have been described. In contrast, other receptors have been neglected, partly due to the lack of suitable genetic tools. Here, for the first time, we compiled a complete set of mutant lines of all known octopamine receptors, all generated using the same genetic tool, the recently established Trojan Exon system. It integrates the Gal4/UAS binary expression strategy while simultaneously impairing receptor func-tion. This enabled us to generate a comprehensive anatomical map of receptor ex-pression in the larva and, at the same time, analyze the function of individual octopa-mine receptors during larval development, chemosensory perception and locomotion. All octopamine receptors (Oamb, Oct2R, Oct{beta}1R, Oct{beta}2R, Oct{beta}3R, and Oct-TyrR) showed extensive signal in the central nervous system. The same was found for the peripheral nervous system, with the exception of Oct{beta}2R, which showed pronounced expression in the somatic muscles. We also observed a previously undescribed role of Oct{beta}1R, Oct{beta}3R, and Oct-TyrR in larval hatching and in the survival of larvae and pupae. Molecular evaluation of the Trojan Exon octopamine lines supports our analy-sis. In addition, we combined the experimental results with gene expression data from the different development stages of Drosophila melanogaster and from different tis-sues and cell populations throughout the body. Overall, we compiled, analyzed and validated a complete set of octopamine lines which, together with gene expression analysis, provides a basis for further functional studies on the larval octopaminergic system.

neuroscience↗

bioRxiv2025

Diet and temperature interactively impact brown adipose tissue gene regulation controlled by DNA methylation

Controlling brown adipose tissue (BAT) plasticity in adulthood holds promising potential for effective new obesity therapies by targeting the mechanisms of adaptive thermogenesis. Recent studies have shown that BAT development and function are under epigenetic control, with DNA methylation linked to the regulation of key thermogenic and metabolic genes. Here we sought to understand how diet and cold exposure interactively shape BAT gene regulation controlled by DNA methylation. Mice (N = 8 per group) were housed under cold exposure (8{degrees}C) or thermoneutrality (30{degrees}C) and fed either chow or high-fat diet (HFD). BAT was isolated for transcriptome (RNAseq) and methylome (RRBS) analyses. We identified differentially methylated and expressed genes (DMEGs) by comparing the effects of cold exposure under chow and high-fat diet, as well as by analyzing the interaction between temperature and diet. Functional pathway enrichment and EpiFactors Database screening were used to assess epigenetic regulators, and candidate gene expression was validated by modulating DNA-methylation in vitro. We identified [~]1,360 differentially expressed genes (DEGs) uniquely affected by the diet-temperature interaction with most downregulated in HFD-fed mice, indicating that obesity limits the transcriptional response of BAT to cold. 65 DMEGs (4% of DEGs) were largely diet-specific in response to cold exposure, suggesting that DNA methylation contributes to a selective layer of gene regulation during BAT adaptation to distinct metabolic states. In HFD-fed mice, DMEGs were enriched in pathways related to mitochondrial dysfunction, altered lipid metabolism, neuroendocrine signaling, and compensatory stress responses, contrasting the adaptive thermogenic profile observed in chow-fed controls. Differentially expressed genes of epigenetic regulators such as Tet2, Dnmt3a and Apobec1 showed diet- and cold-dependent regulation, indicating impaired methylation flexibility under obesogenic conditions. Using cell culture experiments, we confirmed the regulation of gene expression of candidate genes, validating the functional link between DNA methylation and thermogenic gene regulation. This is the first study to demonstrate an epigenetic response to cold exposure that differs by dietary condition, particularly in obesity. Our findings highlight a coordinated transcriptional and epigenetic remodeling of BAT, shaped by both environmental and metabolic signals. These insights may inform targeted epigenetic or nutritional strategies to restore BAT function and would further strengthen our understanding of how these might be used as therapeutic basis to improve metabolic health in obesity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/672110v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1f99b80org.highwire.dtl.DTLVardef@502d02org.highwire.dtl.DTLVardef@1bb0a93org.highwire.dtl.DTLVardef@b34e4c_HPS_FORMAT_FIGEXP M_FIG C_FIG Mice were housed under cold exposure or thermoneutrality and fed either chow or high-fat diet (HFD). RNA sequencing (RNAseq) and reduced representation bisulfite sequencing (RRBS) was performed on brown adipose tissue (BAT) which provide the fundament for the identification of differentially methylated positions (DMP) and regions (DMR) as well as differentially expressed genes (DEG) in three models: COLDchow, comparing 8{degrees} vs 30{degrees}C mice on chow diet; COLDHFD, comparing 8{degrees} vs 30{degrees}C mice on HFD diet and{Delta} COLDdiet, comparing COLDchow vs COLDHFD. Differentially methylated and expressed genes (DMEGs; circos plot shows a representative example) were identified for all comparisons based on those DMPs which correlated significantly with differentially expressed genes (DEGs; the heatmap shows a representative example). DMEGs were taken forward for pathways enrichment analyses and to identify differentially regulated epigenetic regulators using the EpiFactors Database. The figure was created with BioRender.

genomics↗

bioRxiv2025

Podocalyxin and ciliary neurotrophic factor receptor are novel components of the surfaceome of chondrogenic cells

BackgroundOsteoarthritis is a degenerative joint disease characterized by progressive loss of articular cartilage and limited capacity for intrinsic repair. A major barrier to developing effective regenerative strategies is the incomplete understanding of the molecular mechanisms regulating chondrogenesis and cartilage maintenance. Cell surface proteins are key mediators of extracellular communication, adhesion, and signaling, yet the chondrogenic surfaceome remains incompletely mapped, with prior studies focusing primarily on mature or cytokine-activated chondrocytes. The aim of this study was to provide a temporal profile of the surfaceome during in vitro chondrogenic differentiation and to identify novel membrane proteins with potential roles in cartilage biology. MethodsWe applied a sialoglycoprotein-targeted glycocapture strategy to selectively enrich plasma membrane proteins from chick embryonic limb bud-derived micromass cultures undergoing chondrogenesis. Enriched samples underwent high-resolution shotgun proteomic analysis, and differentially expressed candidates were validated by western blotting, immunocytochemistry, and transient gene silencing. Functional effects on extracellular matrix gene regulation were assessed by quantitative RT-PCR and matrix histochemistry. ResultsThis approach generated the first temporal surfaceome map of chondrogenic progenitors. Among identified candidates, two proteins not previously linked to chondrogenesis, podocalyxin (PODXL) and ciliary neurotrophic factor receptor (CNTFR), were detected at the plasma membrane and confirmed at the protein and transcript levels. Both proteins exhibited time-dependent downregulation during differentiation. Targeted knockdown revealed differential regulation of the fibrocartilage marker COL1A1 expression, indicating non-redundant roles in cell-matrix signaling and survival pathways. Single-cell transcriptomic meta-analysis confirmed expression of both proteins in discrete human articular chondrocyte subpopulations. ConclusionsThis study expands the molecular framework of chondrogenesis, identifying PODXL and CNTFR as novel, temporally regulated surfaceome components with distinct roles in extracellular matrix signaling. These findings complement prior proteomic analyses of cytokine-activated mature articular chondrocytes and suggest new candidates for developmental cartilage biomarkers and therapeutic targets for osteoarthritis. Our results provide a resource for future cross-species surfaceome studies and highlight key pathways for further investigation into cartilage lineage specification and matrix adaptation. Plain English SummaryOsteoarthritis is the most common joint disease worldwide, causing pain, stiffness, and reduced mobility as the smooth cartilage that covers the ends of bones gradually breaks down. Cartilage has a very limited ability to heal itself, and there are currently no treatments that can stop or reverse the disease. Scientists are working on new ways to repair or replace damaged cartilage, but to do this effectively, they need to understand the molecular "language" that cartilage-forming cells use to develop and maintain healthy tissue. In this study, we examined the set of proteins that are present on the surface of cartilage-forming cells, known as the "surfaceome." These surface proteins play important roles in how cells connect to their surroundings, receive signals, and work together to build the cartilage matrix. Using a method to selectively capture and analyze these proteins, we discovered two that had never been linked to cartilage development: podocalyxin and ciliary neurotrophic factor receptor. We found that these two proteins may have opposite effects on cartilage quality. Because they can be detected on the outside of cells, they could be developed into markers for early osteoarthritis detection or as targets for new therapies. Our findings open the door to new strategies for diagnosing and treating joint disease by focusing on cell-surface communication.

cell biology↗

bioRxiv2024

Temporal expectations modulate coupling between frontal and sensory brain areas

Temporal prediction enhances perceptual processing by aligning neural excitability with expected sensory events. While local oscillatory mechanisms are known to support timing, less is understood about how large-scale functional brain networks dynamically coordinate predictive processes. In particular, it remains unclear how functional connectivity (FC)--the integration of information into network hubs--differs during expectation formation (post-cue) versus outcome evaluation (post-target), and how this varies across levels of predictability. To investigate this, we recorded electroencephalogram (EEG) while participants performed a cued auditory target-detection task with varying temporal predictability (80% and 50%). Event-related potential (ERP) results revealed that implicit temporal predictability primarily modulated later evaluative processes (P3b, frontal negativity), rather than early sensory components, consistent with context updating under uncertainty. FC was analyzed using a data-driven approach based on Normalized Directed Transfer Entropy (NDTE) applied to EEG difference waveforms between high- and low-predictability conditions. Connectivity was examined separately for the post-cue and post-target periods to distinguish prediction and evaluation phases. Behaviorally, higher temporal predictability facilitated faster reaction times. Connectivity analyses revealed largely overlapping but somewhat distinct network dynamics for prediction and evaluation phases of the signal processing.

neuroscience↗

bioRxiv2024

Sex-specific role of epigenetic modification of a leptin upstream enhancer in the adipose tissue

ObjectiveMaternal hormonal status can have long-term effects on offspring metabolic health, likely regulated via epigenetic mechanisms. We elucidated the effect of maternal thyroid hormones on epigenetic regulation of Leptin (Lep) transcription in adipose tissue (AT) and investigated the role of DNA methylation at a Lep upstream enhancer (UE) in adipocyte biology. MethodsPregnant mice were treated with Triiodothyronine (T3). Offspring body composition and adipose tissue were analysed at 6 months (treatment: N = 8, control: N = 12). DNA methylation at the Lep UE and Lep mRNA levels in gonadal white adipose tissue (gWAT) and leptin serum levels were measured. The Lep UE was hypomethylated in murine preadipocytes using a dCas9-SunTag-TET1 system, followed by differentiation. In human visceral AT samples (N = 52) from the Leipzig Obesity BioBank (LOBB) LEP UE methylation and LEP mRNA levels were assessed alongside leptin serum levels and correlated with body fat percentage. Causal relationships were explored using mediation analysis. ResultsHigh maternal T3 levels reduced offspring body weight, total fat, and gWAT mass. Female offspring of T3-treated mothers showed lower Lep mRNA levels and higher Lep UE methylation compared to controls. CRISPR/dCas9 editing reduced Lep UE methylation by [~]20% in preadipocytes without altering Lep expression or lipid accumulation after differentiation. In humans, a mediation of sex-specific difference in body fat percentage via Lep UE methylation was found. ConclusionMaternal thyroid hormones might affect offspring gWAT Lep expression in a sex-specific manner, potentially driven by DNA methylation at the Lep UE, influencing body fat percentage.

genetics↗

bioRxiv2024

GLP-1 receptor agonist exenatide uncouples food intake from hedonic and anticipatory regulation in non-human primates: Insights from an operant meal schedule paradigm

Glucagon-like peptide 1 (GLP-1), a neuroendocrine signal of energy balance and satiety, has a major role in regulating food intake behaviour. Here we investigated the effects of the GLP-1 agonist exenatide on palatability-driven feeding regulation in adult male rhesus macaques (n=5) using a novel operant food intake paradigm with four meal schedule conditions where two types of pellets with different palatability values were offered as meal in all combinations in two consecutive daily feeding sessions (S1 and S2). In control conditions, a strong, palatability-driven anticipatory effect was found in S1, followed by a complementary positive contrast effect in S2. After acute subcutaneous treatment with 1 {micro}g/kg dose of exenatide 1 h before S1, food intake decreased to the same very low level in all meal schedule conditions in S1, completely erasing the previously observed anticipatory effect. Conversely, exenatide induced hypoglycaemia in an anticipatory meal schedule dependent pattern. Interestingly, the previously observed positive contrast effect was spared in S2, with a weaker residual effect specifically on the consumption of the more palatable pellet type. To conclude, the food intake reducing effects of exenatide may temporally evolve from strong anorectic to weak anhedonic modulations, where hedonic experience and anticipation during the early anorectic phase is conserved but uncoupled from food intake behaviour.

pharmacology and toxicology↗

bioRxiv2023

Impaired updating of working memory representations in individuals with high BMI: evidence for dopaminergic mechanisms

Everyday life requires an adaptive balance between distraction-resistant maintenance of information and the flexibility to update this information when needed. These opposing mechanisms are proposed to be balanced through a working memory gating mechanism. Prior research indicates that obesity may elevate the risk of working memory deficits, yet the underlying mechanisms remain elusive. Dopaminergic alterations have emerged as a potential mediator. However, current models suggest these alterations should only shift the balance in working memory tasks, not produce overall deficits. The empirical support for this notion is currently lacking, however. To address this gap, we pooled data from three studies (N = 320) where participants performed a working memory gating task. Higher BMI was associated with overall poorer working memory, irrespective of whether there was a need to maintain or update information. However, when participants, in addition to BMI level, were categorized based on certain putative dopamine-signaling characteristics (Single Nucleotide Polymorphisms; specifically, Taq1A and DARPP-32), distinct working memory gating effects emerged. These SNPs, primarily associated with striatal dopamine transmission, appear to be linked with differences in updating, specifically, among high-BMI individuals. Moreover, blood amino acid ratio, which indicates central dopamine synthesis capacity, combined with BMI, shifted the balance between distractor-resistant maintenance and updating. These findings suggest that both dopamine-dependent and dopamine-independent cognitive effects exist in obesity. Understanding these effects is crucial if we aim to modify maladaptive cognitive profiles in individuals with obesity.

neuroscience↗

bioRxiv2022

Speech prosody supports speaker selection and auditory stream segregation in a multi-talker situation

To process speech in a multi-talker environment, listeners need to segregate the mixture of incoming speech streams and focus their attention on one of them. Potentially, speech prosody could aid the segregation of different speakers, the selection of the desired speech stream, and detecting targets within the attended stream. For testing these issues, we recorded behavioral responses and extracted event-related potentials and functional brain networks from electroencephalographic signals recorded while participants listened to two concurrent speech streams, performing a lexical detection and a recognition memory task in parallel. Prosody manipulation was applied to the attended speech stream in one group of participants and to the ignored speech stream in another group. Naturally recorded speech stimuli were either intact, synthetically F0-flattened, or suppressed by the speaker. Results show that prosody - especially the parsing cues mediated by speech rate - facilitates stream selection, while playing a smaller role in auditory stream segmentation and target detection.

neuroscience↗

bioRxiv2022

The temporal transcriptomic signature of cartilage formation

Chondrogenesis is a multistep process, in which cartilage progenitor cells generate a tissue with distinct structural and functional properties. Although several approaches to cartilage regeneration rely on the differentiation of implanted progenitor cells, the temporal transcriptomic landscape of in vitro chondrogenesis in different models has not been reported. Using RNA sequencing, we examined differences in gene expression patterns during cartilage formation in micromass cultures of embryonic limb bud-derived progenitors. Principal component and trajectory analyses revealed a progressively different and distinct transcriptome during chondrogenesis. Differentially expressed genes (DEGs), based on pairwise comparisons of samples from consecutive days were classified into clusters and analysed. We confirmed the involvement of the top DEGs in chondrogenic differentiation using pathway analysis and identified several chondrogenesis-associated transcription factors and collagen subtypes that were not previously linked to cartilage formation. Transient gene silencing of ATOH8 or EBF1 on day 0 attenuated chondrogenesis by deregulating the expression of key osteochondrogenic marker genes in micromass cultures. These results provide detailed insight into the molecular mechanism of chondrogenesis in primary micromass cultures and present a comprehensive dataset of the temporal transcriptomic landscape of chondrogenesis, which may serve as a platform for new molecular approaches in cartilage tissue engineering. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/486765v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1b599d5org.highwire.dtl.DTLVardef@18670daorg.highwire.dtl.DTLVardef@15afc12org.highwire.dtl.DTLVardef@5b0791_HPS_FORMAT_FIGEXP M_FIG This study provides insights into the mechanisms of cartilage formation. Gene expression patterns during cartilage formation in micromass cultures were analysed using RNA sequencing. Silencing ATOH8 or EBF1 attenuates chondrogenesis. C_FIG Key points* We examined the global gene expression patterns during in vitro chondrogenesis. * Using WGCNA, we created a module of genes with patterns similar to those of SOX9, ACAN, and COL2A1. * We identified ATOH8 and EBF1 transcription factors with a yet unexplored role in chondrogenesis.

molecular biology↗

bioRxiv2021

PTEN regulates adipocyte progenitor growth, differentiation and cellular aging

The tumor suppressor phosphatase and tensin homolog (PTEN) negatively regulates the insulin signaling pathway. Germline PTEN pathogenic variants cause PTEN Hamartoma Tumor Syndrome (PHTS), associated with lipoma development in children. It remains unclear which mechanisms trigger this aberrant adipose tissue growth. Adipocyte progenitor cells (APCs) lose their capacity to differentiate into adipocytes during continuous culture, while APCs from PHTS patients lipomas retain their adipogenic potential over a prolonged period. To investigate the role of PTEN in adipose tissue development we performed functional assays and RNA sequencing of control and PTEN knockdown APCs. Reduction of PTEN levels using siRNA or CRISPR lead to an enhanced proliferation and differentiation of APCs. FOXO1 was downregulated on the mRNA level while inactivation through phosphorylation increased. FOXO1 phosphorylation initiates the expression of the lipogenesis activating transcription factor SREBP1. SREBP1 levels were higher after PTEN knockdown and may account for the enhanced adipogenesis. To validate this we overexpressed constitutively active FOXO1 in PTEN CRISPR cells and found reduced adipogenesis, accompanied by a SREBP1 downregulation. We observed that PTEN levels were upregulated during long term culture of wild type APCs. PTEN CRISPR cells showed less senescence compared to controls and the senescence marker CDKN1A (p21) was downregulated in PTEN knockdown cells. Cellular senescence was the most significantly enriched pathway found in RNA sequencing of PTEN knockdown vs. control cells. These results provide evidence that PTEN is involved in the regulation of APCs proliferation, differentiation and senescence, thereby contributing to aberrant adipose tissue growth in PHTS patients.

cell biology↗

bioRxiv2020

A Minimally Destructive Protocol for DNA Extraction from Ancient Teeth

Ancient DNA sampling methods--although optimized for efficient DNA extraction--are destructive, relying on drilling or cutting and powdering (parts of) bones and teeth. As the field of ancient DNA has grown, so have concerns about the impact of destructive sampling of the skeletal remains from which ancient DNA is obtained. Due to a particularly high concentration of endogenous DNA, the cementum of tooth roots is often targeted for ancient DNA sampling, but standard destructive sampling methods often result in the loss of at least one entire root. Here, we present a minimally destructive method for extracting ancient DNA from dental cementum present on the surface of tooth roots. This method does not require destructive drilling or grinding, and, following extraction, the tooth remains safe to handle and suitable for most morphological studies, as well as other biochemical studies, such as radiocarbon dating. We extracted and sequenced ancient DNA from 30 teeth (and 9 corresponding petrous bones) using this minimally destructive extraction method in addition to a typical tooth sampling method. We find that the minimally destructive method can provide ancient DNA that is of comparable quality to extracts produced from teeth that have undergone destructive sampling processes. Further, we find that a rigorous cleaning of the tooth surface combining diluted bleach and UV light irradiation seems sufficient to minimize external contaminants usually removed through the physical removal of a superficial layer when sampling through regular powdering methods.

evolutionary biology↗

bioRxiv2017

Widely used commercial ELISA for human Zonulin reacts with Complement C3 rather than pre-Haptoglobin 2

BACKGROUNDThere is increasing evidence for the role of impaired intestinal permeability in obesity and associated metabolic diseases. Zonulin is an established serum marker for intestinal permeability and identical to pre-haptoglobin2. Here, we aimed to investigate the relationship between circulating zonulin and metabolic traits related to obesity.\n\nMETHODSSerum zonulin was measured by using a widely used commercial ELISA kit in 376 subjects from the metabolically well-characterized cohort of Sorbs from Germany. In addition, haptoglobin genotype was determined in DNA samples from all study subjects.\n\nRESULTSAs zonulin concentrations did not correlate to the haptoglobin genotypes, we investigated the specificity of the zonulin ELISA assay using antibody capture experiments, mass spectrometry and Western blot analysis. Using serum samples that gave the highest or lowest ELISA signals, we detected several proteins that are likely to be captured by the antibody in the present kit. However, none of these proteins corresponds to pre-haptoglobin2. We used increasing concentrations of recombinant pre-haptoglobin 2 and complement C3 as one of the representative captured proteins and the ELISA kit did not detect either. Western blot analysis using both the polyclonal antibodies used in this kit and monoclonal antibodies rose against zonulin showed a similar protein recognition pattern but with different intensity of detection. The protein(s) measured using the ELISA kit was (were) significantly increased in patients with diabetes and obesity and correlated strongly with markers of the lipid and glucose metabolism. Combining mass spectrometry and Western blot analysis using the polyclonal antibodies used in the ELISA kit, we identified properdin as another member of the zonulin family.\n\nCONCLUSIONSOur study suggests that the zonulin ELISA does not recognize pre-haptoglobin 2, rather structural (and possibly functional) analogue proteins belonging to the mannose-associated serine protease family, with properdin being the most likely possible candidate.

molecular biology↗

bioRxiv2017

Face inversion reveals holistic processing of peripheral faces

Face perception is accomplished by face-selective neural processes, involving holistic processing that enables highly efficient integration of facial features into a whole face representation. It has been shown that in face-selective regions of the ventral temporal cortex, neural resources involved in holistic processing are primarily dedicated to the central portion of the visual field. These findings raise the intriguing possibility that holistic processing might be the privilege of centrally presented faces and could be strongly diminished in the case of peripheral faces. We addressed this question using the face inversion effect, a well established marker of holistic face processing. The behavioral results revealed impaired identity discrimination performance for inverted peripheral faces scaled according to the V1 magnification factor, compared to upright presented faces. The size of peripheral face inversion effect (FIE) was comparable to that found for centrally displayed faces. Face inversion affected the early ERP responses to faces in two time intervals. The earliest FIE was most pronounced in the time window between 130-140 ms following stimulus presentation, for both centrally and peripherally displayed faces and in the latter case, it was present only over the contralateral hemisphere. The timing of the next component FIE corresponded closely with the temporal interval of the N170 ERP component and showed strong right hemisphere lateralization, both when faces were displayed in the left or right visual field. Furthermore, we also showed that centrally presented face masks impaired peripheral face identity discrimination performance, but did not reduce the magnitude of the FIE. These findings revealed robust behavioral and neural inversion effects for peripheral faces and thus suggest that faces are processed holistically throughout the visual field.\n\nHighlightsRobust behavioral and neural inversion effect was found for peripheral faces.\n\nP1 ERP component is modulated by inverted central and contralateral faces.\n\nN170 ERP component is modulated by centrally and peripherally presented faces.\n\nNeural face inversion effect shows strong right hemisphere lateralization.\n\nFaces are processed holistically throughout the visual field.

neuroscience↗