Biology subjects

van Dijk, E.

Publications and source records attributed to van Dijk, E..

9 recordsLinked to original sources

bioRxiv2026

The BEAC, an epigenetic clock for birds

Epigenetic clocks are powerful tools for estimating both chronological and biological age, enabling the integration of age information into population monitoring, demographic modelling, and research on the ecophysiology and evolution of ageing. Most epigenetic clocks so far have been developed for mammals: here, we present the Bird Epigenetic Ageing Clock (BEAC) for estimating chronological age in avian species. BEAC was established based on genome-wide enzymatic methylation sequencing data of known-age king penguins (Aptenodytes patagonicus), and validated in nine other bird species. The BEAC collects age-informative signals into a bisulfite amplicon sequencing panel of 24 primer pairs, providing a highly accurate and cost-effective alternative to sequencing-intensive approaches. It achieved strong predictive performance in independent king penguin training (R{superscript 2}=0.88; MAE=1.7 years, n=78) and testing data (R{superscript 2}=0.79; MAE=2.3 years, n=41), with negligible batch effects, high longitudinal consistency, and resilience to reduced sample size or missing loci. Importantly, cross-species validation across 180 samples showed that BEAC reliably captures age-associated methylation signals in nine additional bird species across seven clades, demonstrating that a single set of loci can be predictive of ageing across multiple different bird species. BEAC offers a flexible, empirically validated tool and a transferable framework for developing epigenetic clocks in avian species, providing a highly valuable resource for eco-evolutionary studies of ageing in wild species.

molecular biology↗

bioRxiv2025

Sex-specific relationship between melanopsin-dependent light sensitivity and chronotype across the lifespan

Study objectives: Light, acting primarily via melanopsin-mediated signaling, plays a central role in synchronising circadian rhythms. Individuals vary markedly in the sensitivity of their circadian system to light. Whether these differences contribute to the interindividual variability in chronotype, a behavioural manifestation of internal circadian timing, is unclear. The aim of this study was to determine the relationship between melanopsin-dependent light sensitivity and chronotype across the general population. Methods: Participants (adults and children aged [≥] 8 years) were recruited in a science museum. Chronotype was determined using the {micro}MCTQ and the post-illumination pupillary response (PIPR) to short and long-wavelength light stimuli was used as a measure of melanopsin-dependent light sensitivity. The relationship between PIPR and chronotype and their interaction with age and sex were assessed using multiple linear regression. Results: Pupil recordings and questionnaires were available from 457 participants, including 284 adults and 173 children. In adults, the relationship between melanopsin-dependent light sensitivity and chronotype depends on sex and age: in young adult men, greater light sensitivity is linked to a significantly later chronotype, whereas it is significantly associated with an earlier chronotype in older adult women. In children, no evidence was found for a relationship between light sensitivity and chronotype. Conclusions: These findings suggest that individual variation in light sensitivity interacts with sex and age-specific differences in the circadian system and light exposure behaviour to influence circadian timing. Light exposure recommendations should be personalised to take into account these sex and age-specific effects. Statement of significanceWhile individuals differ widely in how their circadian system responds to light, to what extent these individual responses influence internal circadian timing remains unclear. By studying a large and diverse sample of children and adults, our findings reveal that the relationship between light sensitivity and chronotype, a behavioural manifestation of circadian timing, is shaped by both age and sex, offering a more comprehensive understanding of this relationship than previously recognised. Specifically, greater light sensitivity is linked to later chronotype in young men but to earlier chronotype in older women. These results reveal that the impact of light on circadian timing changes across the lifespan and will contribute to the development of personalised light exposure guidelines to promote health and well-being.

neuroscience↗

bioRxiv2025

High-resolution HIV-1 m6A epitranscriptome reveals splicing-dependent methylation clusters and unique 2-LTR transcript modifications

The N6-methyladenosine (m6A) modification of HIV-1 has been widely studied but the number and precise positions of the m6A sites remain unclear due to the lack of precision of detection methods. Using the latest Nanopore chemistry and direct m6A base-calling, we identified 18 m6A: 14 at the 3 end and 4 in central regions of the genome. Our data reveal differential methylation of these positions between splicing isoforms. Eleven of these sites are clustered in two short segments with peak-shaped methylation profiles. Single-molecule analysis revealed that a very small number of transcripts were unmethylated in both clusters. We also identified a [~]732 nt RNA species resulting from the transcription of non-integrated viral DNA circles closed by two long terminal repeats. These transcripts started in the first LTR, terminated at the polyA site of the second LTR and harbored six m6A sites. Five of these sites were present in other transcripts and, remarkably, had the highest methylation rates. The sixth site was methylated only in this transcript, suggesting a role for this RNA in HIV-1 infection. These findings reveal a new landscape of HIV m6A transcriptome modifications and pave the way for studies deciphering their role in the viral life cycle.

bioinformatics↗

bioRxiv2025

Bacterial chromatin remodeling associated with transcription-induced domains at pathogenicity islands

The nucleoid-associated protein H-NS is a bacterial xenogeneic silencer responsible for preventing costly expression of genes acquired through horizontal gene transfer. H-NS silences several Salmonella Pathogenicity Islands (SPIs) essential for host infection. The stochastic expression of SPI-1 is required for invasion of host epithelial cells but complicates investigation of factors involved in SPI-1 chromatin structure and regulation. We performed functional genomics on sorted Salmonella populations expressing SPI-1 or not, to characterize how SPI-1 activation affects chromatin composition, DNA conformation, gene expression and SPI-1 subcellular localization. High H-NS occupancy co-exists with low spurious transcriptional activity and low RNA polymerase occupancy at silent SPIs. Upon SPI-1 activation, remodeling of H-NS occupancy defines a new chromatin landscape, which together with the master SPI-1 regulator HilD, facilitates transcription of SPI-1 genes. SPI-1 activation promotes formation of Transcription Induced Domains accompanied by repositioning SPI-1 close to the nucleoid periphery. We present a model for tightly regulated chromatin remodeling that minimizes the cost of pathogenicity island activation

microbiology↗

bioRxiv2024

A bifunctional snoRNA with separable activities in guiding rRNA 2'-O-methylation and scaffolding gametogenesis effectors

Small nucleolar RNAs are non-coding transcripts that guide chemical modifications of RNA substrates and modulate gene expression at the epigenetic and post-transcriptional levels. However, the extent of their regulatory potential and the underlying molecular mechanisms remain poorly understood. Here, we identify a conserved, previously unannotated intronic C/D-box snoRNA, termed snR107, hosted in the fission yeast long non-coding RNA mamRNA and carrying two independent cellular functions. On the one hand, snR107 guides site-specific 25S rRNA 2-O-methylation and promotes pre-rRNA processing and 60S subunit biogenesis. On the other hand, snR107 associates with the gametogenic RNA-binding proteins Mmi1 and Mei2, mediating their reciprocal inhibition and restricting meiotic gene expression during sexual differentiation. Both functions require distinct cis-motifs within snR107, including a conserved 2-O-methylation guiding sequence. Together, our results position snR107 as a dual regulator of rRNA modification and gametogenesis effectors, expanding our vision on the non-canonical functions exerted by snoRNAs in cell fate decisions.

molecular biology↗

bioRxiv2024

Dual RNA-seq study of the dynamics of coding and non-coding RNAs expression during Clostridioides difficile infection in a mouse model

Clostridioides difficile is the leading cause of healthcare associated diarrhoea in industrialized countries. Many questions remain to be answered about the mechanisms governing its interaction with the host during infection. Non-coding RNAs (ncRNAs) contribute to shaping virulence in many pathogens and modulate host responses, however, their role in C. difficile infection (CDI) has not been explored. To better understand the dynamics of ncRNAs expression contributing to C. difficile infectious cycle and host response, we used a dual RNA- seq approach in a conventional murine model. From the pathogen side, this transcriptomic analysis revealed the upregulation of virulence factors, metabolism and sporulation genes, as well as the identification of 61 ncRNAs differentially expressed during infection that correlated with the analysis of available raw RNA-seq datasets from two independent studies. From these data we identified 118 potential new transcripts in C. difficile including 106 new ncRNA genes. From the host side, we observed the induction of several pro-inflammatory pathways and, among the 185 differentially expressed ncRNAs, the overexpression of microRNAs (miRNAs) previously associated to inflammatory responses or unknown long ncRNAs and miRNAs. A particular host gene expression profile could be associated to the symptomatic infection. In accordance, the metatranscriptomic analysis revealed specific microbiota changes accompanying CDI and specific species associated with symptomatic infection in mice. This first adaptation of in vivo dual RNA-seq to C. difficile contributes to unravelling the regulatory networks involved in C. difficile infectious cycle and host response and provides valuable resources for further studies of RNA-based mechanisms during CDI. ImportanceClostridioides difficile is a major cause of nosocomial infections associated with antibiotic therapy classified as an urgent antibiotic resistance threat. This pathogen interacts with host and gut microbial communities during infection, but the mechanisms of these interactions remain largely to be uncovered. Noncoding RNAs contribute to bacterial virulence and host responses, but their expression has not been explored during C. difficile infection. We took advantage of the conventional mouse model of C. difficile infection to look simultaneously to the dynamics of gene expression in pathogen, its host and gut microbiota composition providing valuable resources for future studies. We identified a number of ncRNAs that could mediate the adaptation of C. difficile inside the host and the crosstalk with the host immune response. Promising inflammation markers and potential therapeutic targets emerged from this work open new directions for RNA-based and microbiota-modulatory strategies to improve the efficiency of C. difficile infection treatments.

microbiology↗

bioRxiv2024

Evolutionary trajectories of IDH-mutant astrocytoma identify molecular grading markers related to cell cycling

1To study the evolutionary processes that drive malignant progression of IDH-mutant astrocytomas, we performed multi-omics on a large cohort of matched initial and recurrent tumor samples. The overlay of genetic, epigenetic, transcriptomic and proteomic data, combined with single-cell analysis, have identified overlapping features associated with malignant progression. These features are derived from three molecular mechanisms and provide a rationale of the underlying biology of tumor malignancy: cell-cycling, tumor cell (de-)differentiation and remodeling of the extracellular matrix. Specifically, DNA-methylation levels decreased over time, predominantly in tumors with malignant transformation and co-occurred with poor prognostic genetic events. DNA-methylation was lifted from specific loci associated with DNA replication and was associated with an increased RNA and protein expression of cell cycling associated genes. All results were validated on samples of newly diagnosed IDH-mutant astrocytoma patients included the CATNON randomized phase 3 clinical trial. Importantly, malignant progression was hardly affected by radio- or chemotherapy, indicating that treatment does not affect the course of disease. Our results culminate in a DNA-methylation based signature for objective tumor grading.

cancer biology↗

bioRxiv2024

Karyotype Evolution in Response to Chemoradiotherapy and Upon Recurrence of Esophageal Adenocarcinomas.

The genome of esophageal adenocarcinoma (EAC) is highly unstable and might evolve over time. Here, we track karyotype evolution in EACs in response to treatment and upon recurrence through multi-region and longitudinal analysis. To this end, we introduce L-PAC, a bio-informatics technique that allows inference of absolute copy number aberrations (CNA) of low-purity samples by leveraging information of high-purity samples from the same cancer. Quantitative analysis of matched absolute CNAs reveals that the amount of karyotype evolution induced by chemoradiotherapy (CRT) is predictive for early recurrence and depends on the initial level of karyotype intra-tumor heterogeneity. We observe that CNAs acquired in response to CRT are partially reversed back to the initial state upon recurrence. CRT hence alters the fitness landscape to which tumors can adjust by adapting their karyotype. Together, our results indicate that karyotype plasticity contributes to therapy resistance of EACs.

bioinformatics↗

bioRxiv2017

The evolution of the temporal program of genome replication

Comparative analyses of temporal programs of genome replication revealed either a nearly complete conservation between closely related species or a comprehensive reprogramming between distantly related species. Therefore, many important questions on the evolutionary remodeling of replication timing programs remain unanswered. To address this issue, we generated genome-wide replication timing profiles for ten yeast species from the genus Lachancea, covering a continuous evolutionary range from closely related to more divergent species. The comparative analysis of these profiles revealed that the replication program linearly evolves with increasing evolutionary divergence between these species. We found that the evolution of the timing program mainly results from a high evolutionary turnover rate of the cohort of active replication origins. We detected about one thousand evolutionary events of losses of active replication origins and gains of newborn origins since the species diverged from their last common ancestor about 80 million years ago. We show that the relocation of active replication origins is independent from synteny breakpoints, suggesting that chromosome rearrangements did not drive the evolution of the replication programs. Rather, origin gains and losses are linked both in space, along chromosomes, and in time, along the same branches of the phylogenetic tree. New origins continuously arise with on average low to medium firing efficiencies and increase in efficiency and earliness as they evolutionarily age. Yet, a subset of newborn origins emerges with high firing efficiency and origin losses occur concomitantly to their emergence and preferentially in their direct chromosomal vicinity. These key findings on the evolutionary birth, death and conservation of active replication origins provide the first description of how the temporal program of genome replication has evolved in eukaryotes.

evolutionary biology↗