Biology subjects

Ramirez, F.

Publications and source records attributed to Ramirez, F..

12 recordsLinked to original sources

bioRxiv2025

CRISPR screen identifies BAP1 as a deubiquitinase regulating SPIN4 stability

Protein homeostasis is tightly controlled by the coordinated actions of E3 ubiquitin ligases and deubiquitinases (DUBs). We identify Spindlin-4 (SPIN4), a histone H3K4me3 reader, as a substrate regulated by opposing pathways: degradation mediated by the Cullin-RING E3 ligase DCAF16 and stabilization by the DUB BAP1. Through CRISPR-Cas9 knockout screens and biochemical analyses, we demonstrate that DCAF16 promotes SPIN4 degradation, while BAP1 interacts with and stabilizes SPIN4 through its catalytic activity. Inhibition or loss of BAP1 reduces SPIN4 levels, highlighting its critical role in maintaining SPIN4 homeostasis. Proteomics and interactome analyses further support this regulatory axis. These findings reveal a dynamic balance controlling SPIN4 stability, with potential implications for epigenetic regulation and disease processes.

biochemistry↗

bioRxiv2025

AXL-GAS6/PROS1 Interaction: A Critical Switch Between Aberrant- and Healthy Repair Following Alveolar Lung Injury

RationaleIdiopathic pulmonary fibrosis (IPF) is a progressive lung disease characterized by aberrant alveolar repair and excessive fibrosis. The TAM-family receptor tyrosine kinase AXL, activated by GAS6 and PROS1, is implicated in tissue remodeling, but ligand-specific AXL signaling during alveolar repair remains poorly defined. ObjectivesTo investigate ligand specific AXL signaling in IPF and how it impacts epithelial proliferation and repair after alveolar injury in-vivo and in-vitro. MethodsSingle cell RNA sequencing was utilized to understand cell specific expression patterns in IPF patients, followed by functional studies in primary human cell culture and functional spatial digital profiling (FuncOmap) analysis in patient tissue. Longitudinal assessment of repair process after alveolar-specific injury in-vivo was used to complement the in-vitro approach. ResultsAXL expression showed enrichment in basal and aberrant basaloid cells of IPF patients. In-vitro GAS6 increased proliferation of basal cells, while PROS1 counteracted this effect. FuncOmap analysis demonstrates direct in-situ interactions between AXL and both ligands, providing evidence for biological relevance. Investigating longitudinal repair processes in-vivo revealed dynamic regulation of AXL ligands as well as AXL. ConclusionsThese findings highlight the importance of ligand-specific AXL signaling in lung repair and suggest that it dysregulation may contribute to IPF pathogenesis, offering potential therapeutic targets for restoring normal repair processes.

molecular biology↗

bioRxiv2024

Mutualisms within light microhabitats drive sensory convergence in a mimetic butterfly community

Niche partitioning within variable habitats can expose species to distinct sensory information. Vision is the primary sensory modality used by many animals to interact with their habitat. However, within diurnal terrestrial ecosystems, little is known if, and how, variation in light environments impact species assemblages and visual system evolution. By studying a diverse, sympatric community of mimetic butterflies, we demonstrate that forest architecture creates a mosaic of light microhabitats that drive adaptive sensory convergence and divergence in both peripheral and central sensory systems. Our study provides insights into the dynamic response of visual systems when confronted with similar ecological challenges, and illustrates the wide-reaching consequences of interspecific mutualisms, such as mimicry, on organismal evolution.

evolutionary biology↗

bioRxiv2024

JUNB O-GlcNAcylation-mediated promoter accessibility of metabolic genes modulates distinct epithelial lineage in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with substantial unmet medical needs. While aberrant epithelial remodelling is a key factor in IPF progression, the molecular mechanisms behind this process remain elusive. Using a patient-derived 3D distal airway epithelial organoid model, we successfully recapitulate important IPF features, including the emergence of aberrant KRT5+/COL1A1+ basal cells and a metabolic shift towards increased O-linked {beta}-N-acetylglucosamine (O-GlcNAc) levels. Consistent with this, single-cell analysis of accessible chromatin reveals an increased chromatin accessibility in these aberrant basal cells, particularly at JUNB motif-enriched promoter regions of metabolic genes. O-GlcNAcylation shapes JUNB function and promotes a pro-fibrotic response to chronic injury, leading to aberrant epithelial remodelling. Site-specific deletion of O-GlcNAcylation on JUNB attenuates the metaplastic differentiation of basal cells, thereby aiding in the restoration of the alveolar lineage. Together, these data establish a novel link between metabolic dysregulation, mediated by the O-GlcNAc-JUNB axis, and bronchiolization in IPF, offering new therapeutic strategies to treat this fatal disease.

cell biology↗

bioRxiv2023

Spatial Transcriptomic Characterization of Novel Pathologic Niches in IPF

An unmet medical need persists in Idiopathic Pulmonary fibrosis (IPF), for which treatments additional to anti-fibrotic therapy are needed. Single cell RNA sequencing (scRNA-seq) has advanced our understanding of IPF with cell type-specific insights but lacks cellular tissue context. Spatial transcriptomics addresses this by providing spatially resolved gene expression, enabling gene and cell type localization within the tissue environment. We profiled IPF and control patient lung tissue sections using spatial transcriptomics and combined the data with an atlas of integrated IPF scRNA-seq datasets. Through computational analysis, we identified three disease-associated pathologic niches with unique cellular composition / localization and analyzed their cell-cell communication. We identified the Fibrotic niche, comprising Myofibroblasts and Aberrant Basaloid cells, preferentially located around airways and close to the Airway Macrophage niche in the lumen, containing SPP1+ Macrophages. We also identified the Immune niche, distinct foci of lymphoid cells in fibrotic tissue, surrounded by remodeled endothelial vessels. TEASERSpatial transcriptomics localizes genes and cell types in the tissue and identifies pathological cellular niches in IPF and control lungs.

systems biology↗

bioRxiv2022

Mapping mitonuclear epistasis using a novel recombinant yeast population

Natural genetic variation in mitochondrial and nuclear genomes can influence phenotypes by perturbing coadapted mitonuclear interactions. Mitonuclear epistasis, i.e. non-additive phenotype effects of interacting mitochondrial and nuclear alleles, is emerging as a general feature in eukaryotes, yet very few mitonuclear loci have been identified. Here, we present a novel advanced intercrossed population of S. cerevisiae yeasts, called the Mitonuclear Recombinant Collection (MNRC), designed explicitly for detecting mitonuclear loci contributing to complex traits, and use this population to map the genetic basis to mtDNA loss. In yeast, spontaneous deletions within mtDNAs lead to the petite phenotype that heralded mitochondrial research. We show that in natural populations, rates of petite formation are variable and influenced by genetic variation in nuclear, mtDNAs and mitonuclear interactions. We then mapped nuclear and mitonuclear alleles contributing mtDNA stability using the MNRC by integrating mitonuclear epistasis into a genome-wide association model. We found that associated mitonuclear loci play roles in mitotic growth most likely responding to retrograde signals from mitochondria, while associated nuclear loci with main effects are involved in genome replication. We observed a positive correlation between growth rates and petite frequencies, suggesting a fitness tradeoff between mitotic growth and mtDNA stability. We also found that mtDNA stability was influenced by a mobile mitochondrial GC-cluster that is expanding in certain populations of yeast and that selection for nuclear alleles that stabilize mtDNA may be rapidly occurring. The MNRC provides a powerful tool for identifying mitonuclear interacting loci that will help us to better understand genotype-phenotype relationships and coevolutionary trajectories. Author SummaryGenetic variation in mitochondrial and nuclear genomes can perturb mitonuclear interactions and lead to phenotypic differences between individuals and populations. Despite their importance to most complex traits, it has been difficult to identify the interacting loci. Here, we created a novel population of yeast designed explicitly for mapping mitonuclear loci contributing to complex traits and used this population to map genes influencing the stability of mitochondrial DNA (mtDNA). We found that mitonuclear interacting loci were involved in mitotic growth while non-interacting loci were involved in genome replication. We also found evidence that selection for mitonuclear loci that stabilize mtDNAs occurs rapidly. This work provides insight into mechanisms underlying maintenance of mtDNAs. The mapping population presented here is an important new resource that will help to understand genotype/phenotype relationships and coevolutionary trajectories.

evolutionary biology↗

bioRxiv2020

A single-cell RNA-seq Training and Analysis Suite using the Galaxy Framework

BackgroundThe vast ecosystem of single-cell RNA-seq tools has until recently been plagued by an excess of diverging analysis strategies, inconsistent file formats, and compatibility issues between different software suites. The uptake of 10x Genomics datasets has begun to calm this diversity, and the bioinformatics community leans once more towards the large computing requirements and the statistically-driven methods needed to process and understand these ever-growing datasets. ResultsHere we outline several Galaxy workflows and learning resources for scRNA-seq, with the aim of providing a comprehensive analysis environment paired with a thorough user learning experience that bridges the knowledge gap between the computational methods and the underlying cell biology. The Galaxy reproducible bioinformatics framework provides tools, workflows and trainings that not only enable users to perform one-click 10x preprocessing, but also empowers them to demultiplex raw sequencing from custom tagged and full-length sequencing protocols. The downstream analysis supports a wide range of high-quality interoperable suites separated into common stages of analysis: inspection, filtering, normalization, confounder removal and clustering. The teaching resources cover an assortment of different concepts from computer science to cell biology. Access to all resources is provided at the singlecell.usegalaxy.eu portal. ConclusionsThe reproducible and training-oriented Galaxy framework provides a sustainable HPC environment for users to run flexible analyses on both 10x and alternative platforms. The tutorials from the Galaxy Training Network along with the frequent training workshops hosted by the Galaxy Community provide a means for users to learn, publish and teach scRNA-seq analysis. Key PointsO_LISingle-cell RNA-seq has stabilised towards 10x Genomics datasets. C_LIO_LIGalaxy provides rich and reproducible scRNA-seq workflows with a wide range of robust tools. C_LIO_LIThe Galaxy Training Network provides tutorials for the processing of both 10x and non-10x datasets. C_LI

bioinformatics↗

bioRxiv2019

Hi-C guided assemblies reveal conserved regulatory topologies on X and autosomes despite extensive genome shuffling

Genome rearrangements that occur during evolution impose major challenges on regulatory mechanisms that rely on three-dimensional genome architecture. Here, we developed a scaffolding algorithm and generated chromosome-length assemblies from Hi-C data for studying genome topology in three distantly related Drosophila species. We observe extensive genome shuffling between these species with one synteny breakpoint after approximately every six genes. A/B compartments, a set of large gene-dense topologically associating domains (TADs) and spatial contacts between high-affinity sites (HAS) located on the X chromosome are maintained over 40 million years, indicating architectural conservation at various hierarchies. Evolutionary conserved genes cluster in the vicinity of HAS, while HAS locations appear evolutionarily flexible, thus uncoupling functional requirement of dosage compensation from individual positions on the linear X chromosome. Therefore, 3D architecture is preserved even in scenarios of thousands of rearrangements highlighting its relevance for essential processes such as dosage compensation of the X chromosome.

genomics↗

bioRxiv2018

Ultra-parallel ChIP-seq by barcoding of intact nuclei

Chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) is an invaluable tool for mapping chromatin-associated proteins. However, sample preparation is still a largely individual and labor-intensive process that hinders assay throughput and comparability. Here, we present a novel method for ultra-parallelized high-throughput ChIP-seq that addresses the aforementioned problems. The method, called RELACS (Restriction Enzyme-based Labeling of Chromatin in Situ), employs barcoding of chromatin within intact nuclei extracted from different sources (e.g. tissues, treatments, time points). Barcoded nuclei are pooled and processed within the same ChIP, for maximal comparability and significant workload reduction. The choice of user-friendly, straightforward, enzymatic steps for chromatin fragmentation and barcoding makes RELACS particularly suitable for implementation large-scale clinical studies and scarce samples. RELACS can generate ChIP-seq libraries from hundreds of samples within three days and with less than 1000 cells per sample.

genomics↗

bioRxiv2018

Partially methylated domains are hallmarks of a cell specific epigenome topology

BackgroundPartially methylated domains, PMDs, are extended regions in the genome exhibiting a reduced average DNA-methylation level. PMDs cover gene-poor and transcriptionally inactive regions and tend to be heterochromatic. Here, we present a first comprehensive comparative analysis of PMDs across more than 190 WGBS methylomes of human and mouse cells providing a deep insight into structural and functional features associated with PMDs.\n\nResultsPMDs are ubiquitous signatures covering up to 75% of the genome in human and mouse cells irrespective of their tissue or cell origin. Additionally, each cell type comes with a distinct set of specific PMDs, and genes expressed in such PMDs show a strong cell type effect. Demethylation strength varies in PMDs with a tendency towards a more pronounced effect in differentiating and replicating cells. The strongest demethylation is observed in highly proliferating and immortal cancer cell lines. A decrease of DNA-methylation within PMDs tends to be linked to an increase in heterochromatic histone marks and a decrease of gene expressions. Characteristic combinations of heterochromatic signatures in PMDs are linked to domains of early, middle and late DNA-replication.\n\nConclusionPMDs are prominent signatures of long-range epigenomic organization. Integrative analysis identifies PMDs as important general, lineage- and cell-type specific topological features. PMD changes are hallmarks of cell differentiation. Demethylation of PMDs combined with increased heterochromatic marks is a feature linked to enhanced cell proliferation. In combination with broad histone marks PMDs demarcate distinct domains of late DNA-replication.

bioinformatics↗

bioRxiv2017

Community-driven data analysis training for biology

The primary problem with the explosion of biomedical datasets is not the data itself, not computational resources, and not the required storage space, but the general lack of trained and skilled researchers to manipulate and analyze these data. Eliminating this problem requires development of comprehensive educational resources. Here we present a community-driven framework that enables modern, interactive teaching of data analytics in life sciences and facilitates the development of training materials. The key feature of our system is that it is not a static but a continuously improved collection of tutorials. By coupling tutorials with a web-based analysis framework, biomedical researchers can learn by performing computation themselves through a web-browser without the need to install software or search for example datasets. Our ultimate goal is to expand the breadth of training materials to include fundamental statistical and data science topics and to precipitate a complete re-engineering of undergraduate and graduate curricula in life sciences.

bioinformatics↗

bioRxiv2017

High-resolution TADs reveal DNA sequences underlying genome organization in flies

Eukaryotic chromatin is partitioned into domains called TADs that are broadly conserved between species and virtually identical among cell types within the same species. Previous studies in mammals have shown that the DNA binding protein CTCF and cohesin contribute to a fraction of TAD boundaries. Apart from this, the molecular mechanisms governing this partitioning remain poorly understood. Using our new software, HiCExplorer, we annotated high-resolution (570 bp) TAD boundaries in flies and identified eight DNA motifs enriched at boundaries. Known insulator proteins bind five of these motifs while the remaining three motifs are novel. We find that boundaries are either at core promoters of active genes or at non-promoter regions of inactive chromatin and that these two groups are characterized by different sets of DNA motifs. Most boundaries are present at divergent promoters of constitutively expressed genes and the gene expression tends to be coordinated within TADs. In contrast to mammals, the CTCF motif is only present on 2% of boundaries in flies. We demonstrate that boundaries can be accurately predicted using only the motif sequences, along with open chromatin, suggesting that DNA sequence encodes the 3D genome architecture in flies. Finally, we present an interactive online database to access and explore the spatial organization of fly, mouse and human genomes, available at http://chorogeome.ie-freiburg.mpg.de.

genomics↗