Biology subjects

Segura, J.

Publications and source records attributed to Segura, J..

7 recordsLinked to original sources

bioRxiv2026

EpiFlow: multidimensional single-cell epigenetic profiling by spectral flow cytometry

The epigenetic landscape of individual cells determines their identity and function, yet current methods for profiling chromatin modifications at single-cell resolution remain low-throughput, costly, or limited in parametric depth. Here we present EpiFlow, a spectral flow cytometry-based platform that enables the simultaneous quantification of 16 epigenetic markers, including histone post-translational modifications, DNA methylation, and hydroxymethylation, at the single-cell level. We demonstrate that EpiFlow is robust across species from yeast to mammals and resolves biologically meaningful epigenetic transitions during the cell cycle, stem cell differentiation, germinal centre B cell maturation, diabetic liver remodelling, and seizure-induced chromatin reprogramming. High-dimensional integration of EpiFlow data enables cell-type classification based solely on epigenetic profiles in liver, brain, blood, and cancer. Furthermore, EpiFlow detects on-target and off-target/indirect effects of epigenetic drugs in a high-throughput-compatible format. Collectively, these results establish EpiFlow as a broadly applicable platform for single-cell epigenetic analysis in basic, pharmaceutical, and translational research.

cell biology↗

bioRxiv2025

Slow RNAPII elongation enhances naive-pluripotency rewiring while preserving replication fork speed

DNA replication and transcription must be intricately coordinated, as both machineries navigate the same chromatin landscape to ensure genome stability and proper cell function. Here, we uncover that a global imbalance between their elongation rates-- specifically, slowed transcriptional elongation alongside rapid replication fork progression--does not elicit replicative stress. Instead, this uncoupling accelerates the acquisition of naive pluripotency during in vitro de-differentiation, revealing an unexpected link between transcription kinetics and cell plasticity. Mechanistically, we show that the transition to naive pluripotency is accompanied by a distinctive alternative splicing program indicative of reduced RNAPII elongation, both in vitro and in vivo. These findings redefine the functional relationship between replication and transcription dynamics and uncover transcriptional velocity as a tunable layer of control over cellular identity transitions. HighlightsO_LIReplication and transcription elongation rates can be uncoupled genome-wide. C_LIO_LISlow transcription elongation accelerates the acquisition of naive pluripotency during in vitro de-differentiation. C_LIO_LIHigh replication fork speed is maintained in slow-transcribing cells during cell state transitions. C_LIO_LIAlternative splicing is distinctly regulated at the naive and primed pluripotency states, both in vitro and in vivo. C_LI

molecular biology↗

bioRxiv2025

Multi-scale structural similarity embedding search across entire proteomes

The rapid expansion of three-dimensional (3D) biomolecular structure information, driven by breakthroughs in artificial intelligence/deep learning (AI/DL)-based structure predictions, has created an urgent need for scalable and efficient structure similarity search methods. Traditional alignment-based approaches, such as structural superposition tools, are computationally expensive and challenging to scale with the vast number of available macromolecular structures. Herein, we present a scalable structure similarity search strategy designed to navigate extensive repositories of experimentally determined structures and computed structure models predicted using AI/DL methods. Our approach leverages protein language models and a deep neural network architecture to transform 3D structures into fixed-length vectors, enabling efficient large-scale comparisons. Although trained to predict TM-scores between single-domain structures, our model generalizes beyond the domain level, accurately identifying 3D similarity for full-length polypeptide chains and multimeric assemblies. By integrating vector databases, our method facilitates efficient large-scale structure retrieval, addressing the growing challenges posed by the expanding volume of 3D biostructure information.

bioinformatics↗

bioRxiv2023

Nucleosomal DNA has topological memory

One fundamental yet elusive aspect of the chromosome architecture is the constrained topolome, which refers to how chromatin elements restrain DNA topology. Nucleosomes stabilise negative DNA supercoils, with most nucleosomes typically restraining a DNA linking number difference ({Delta}Lk) of about -1.26. However, whether this capacity is uniform across the genome is unknown. Here, we calculated the {Delta}Lk restrained by over 4000 nucleosomes in yeast cells. To achieve this, we placed each nucleosome in a circular minichromosome and performed Topo-seq, a novel high-throughput procedure to inspect the topology of circular DNA libraries in a single gel electrophoresis. We found that nucleosomes inherently restrain distinct {Delta}Lk values depending on their genomic origin. Nucleosome DNA topologies differ significantly at gene bodies ({Delta}Lk=-1.29), intergenic regions ({Delta}Lk=-1.23), rDNA genes ({Delta}Lk=-1.24) and telomeric regions ({Delta}Lk=-1.07). Nucleosomes nearby the transcription start and termination sites also exhibit singular DNA topologies. These findings demonstrate that nucleosome DNA topology is imprinted by its native chromatin context and persists even when the nucleosome is relocated. This imprinting contributes to nucleosome functional roles and chromatin folding architectures.

molecular biology↗

bioRxiv2022

Condensin pinches a short negatively supercoiledDNA loop during each round of ATP usage

Condensin extrudes DNA loops using an ATP-dependent mechanism that remains to be elucidated. Here, we show how condensin activity alters the topology of the interacting DNA. High condensin concentrations restrain DNA positive supercoils. However, in experimental conditions that sustain DNA loop extrusion, condensin restrains negative supercoils. Namely, upon ATP-mediated loading onto DNA, each condensin constrains a DNA linking number difference ({Delta}Lk) of -0.4. This {Delta}Lk increases to -0.8 during ATP binding and resets to -0.4 upon ATP hydrolysis. These {Delta}Lk values reflect the transient formation of a short left-handed loop of DNA, which is not the extruding loop. We conclude that, upon condensin ATPase-head engagement, a segment of DNA is pinched to form a short negatively supercoiled loop, which can be subsequently merged with the extruding loop. Such "pinch and merge" mechanism implies that the DNA is transferred between two dynamic DNA-binding sites while anchored at a third site.

molecular biology↗

bioRxiv2022

Assessment of dynamics of global DNA methylation during the cryopreservation process of Pinus pinaster embryogenic lines

Long-term in vitro maintenance of embryogenic lines of Pinus species has been associated with lower maturation capacity, because of this, cryopreservation protocols for the embryogenic lines are needed to maintain valuable genotypes. Since cryopreservation may induce epigenetic variations, we evaluate changes in DNA methylation levels through the course of the cryopreservation of maritime pine embryogenic lines, as compared to those lines maintained by repeated subcultures. Six maritime pine embryogenic lines were cryopreserved following a protocol that includes pre-treatments inducing osmotic stress in liquid media. The percentage of methylated cytosines (%5-mC) in total DNA was determined by using a colorimetric assay. Reactive oxygen species (ROS) accumulation in cell lines was also determined by quantifying dihydroethidium (DHE) fluorescence under a confocal laser-scanning microscope. In the first experiment, we found that global DNA methylation was significantly reduced during the cryopreservation protocol. Subsequently, we evaluated the methylation status of both cryopreserved and no cryopreserved lines (maintained by subcultures) and found differences among embryogenic lines but overall, cryopreservation did not alter %5-mC of the recovered lines while periodical subcultures increased methylation rates. In addition, maltose pretreatment did not increase significantly ROS production in embryogenic lines. Our results demonstrate that the genetic stability during cryopreservation highly depends on the embryogenic line studied, but the protocol allows maintaining methylation DNA rates in most of the recovered lines.

plant biology↗

bioRxiv2019

MicrographCleaner: a python package for cryo-EM micrograph segmentation using deep learning

Cryo-EM Single Particle Analysis workflows require from tens of thousands of high-quality particle projections to unveil the three-dimensional structure of macromolecules. Conventional methods for automatic particle picking tend to suffer from high false-positive rates, hurdling the reconstruction process. One common cause of this problem is the presence of carbon and different types of high-contrast contaminations. In order to overcome this limitation, we have developed MicrographCleaner, a deep learning package designed to discriminate which regions of micrographs are suitable for particle picking and which are not in an automatic fashion. MicrographCleaner implements a U-net-like deep learning model trained on a manually curated dataset compiled from over five hundred micrographs. The benchmarking, carried out on about one hundred independent micrographs, shows that MicrographCleaner is a very efficient approach for micrograph preprocessing. MicrographCleaner (micrograph_cleaner_em) package is available at PyPI and Anaconda Cloud and also as a Scipion/Xmipp protocol. Source code is available at https://github.com/rsanchezgarc/micrograph_cleaner_em.

bioinformatics↗