Biology subjects

Sandelin, A.

Publications and source records attributed to Sandelin, A..

15 recordsLinked to original sources

bioRxiv2026

SurpHer: a genetically encoded ratiometric sensor for dynamic extracellular pH imaging

Extracellular pH is a key microenvironmental factor shaping cell physiology and disease, creating a need for quantitative biosensors that can capture dynamic changes in pHe at the surface of individual living cells. Here, we develop a genetically encoded, ratiometric extracellular pH biosensor through systematic screening of a modular library of membrane-display designs that combine SEpHluorin with a pH-stable reference fluorophore. Screening identified a cell-surface-localised mKate2-SEpHluorin construct, named SurpHer, that exhibits dynamic ratiometric responses across the pHe range of 6 - 7.8. SurpHer shows robust membrane localisation and extracellular pH responsiveness across diverse human cell types including HEK293T, PANC-1 and MDA-MB231 cells. Following stable integration in MDA-MB-231 cells, SurpHer enabled time-course imaging of pHe gradients in a microfluidic platform for modelling tumour microenvironments. SurpHer enables real-time interrogation of the pericellular pH environment of tumor cells and, more broadly, provides a strategy to probe microenvironmental pH dynamics across diverse biological contexts.

cell biology↗

bioRxiv2026

Mapping active cis-regulatory elements from transcription initiation events

Determining the activity of cis-regulatory elements (CREs) is essential for modeling gene regulation and interpreting genetic variation. Yet, current methods often lack the specificity to distinguish active regulation from permissive chromatin, the sensitivity to detect unstable enhancer RNAs, or the scalability required to profile limited input material and primary cells. Here, we introduce nucCAGE, a transcription start site (TSS) assay for profiling nuclear, capped RNAs, and PRIME, a computational framework for identifying active CREs from TSS data. Together, these methods increase sensitivity to low-abundance RNAs and enable robust detection of active regulatory elements across diverse contexts. Across multiple orthogonal functional and genetic benchmarks, including fine-mapped eQTLs, ClinVar variants, GWAS loci, and CRISPRi-tested elements, nucCAGE-derived PRIME predictions achieve superior recall compared to state-of-the-art methods while maintaining strong enrichment for phenotype-associated variation. Applying PRIME to the FANTOM5 dataset yields a comprehensive, cell-type-resolved atlas of active CREs that recapitulates known tissue-trait relationships. We demonstrate how this atlas can be used to nominate causal noncoding variants, linking immune-cell enhancer regulation of SMAD3 to asthma and NCOR2 to premature separation of placenta. Together, nucCAGE and PRIME provide a framework for high-sensitivity genome-wide discovery of active CREs and a resource for variant-to-function studies.

genomics↗

bioRxiv2025

A microfluidic model to recapitulate pH and oxygen gradients in solid tumors

The tumor microenvironment (TME) plays critical roles in cancer development, aggressiveness, and treatment resistance. The TME comprises cellular (stromal) components as well as gradients of physicochemical properties, including hypoxia and acidosis. Understanding of how hypoxia and acidosis gradients impact cancer phenotypes is lacking, in large part due to challenges in precisely mimicking and controlling such gradients in a manner compatible with the growth of cancer- and stromal cells. Here, we design and validate a microfluidic device enabling orthogonal gradients of oxygen and pH. Both gradients are established by diffusion from a nearby source and sink in the observation area in the absence of flow. This produces linear gradients at steady state. Our device enables a wide range of spatiotemporally resolved analyses, from omics to live cell imaging, interrogating the impact of the physicochemical TME on disease development. The design is easily adaptable, making it valuable for a wide range of questions involving physicochemical gradients.

cancer biology↗

bioRxiv2025

Regulatory elements of pancreas development license the initiation of pancreatic ductal adenocarcinoma

Cellular plasticity and transitional cellular states are crucial for tissue regeneration across multiple organs. In the pancreas, oncogenic Kras hijacks this program, acting on tissue-specific enhancers to prevent the resolution of acinar-to-ductal metaplasia (ADM) and lock regeneration into a pro-inflammatory state that progresses to cancer. Enhancer transcription, an early event during cellular state transitions, can generate stable enhancer-associated long noncoding RNAs (lncRNAs) positioned near key transcription factors and chromatin contact boundaries, often enriched for disease-associated variants. While enhancer-associated lncRNAs have been implicated in transcriptional regulation and genome organization, their role in pancreas regeneration and cancer initiation has remained unexplored. In this study, we investigated the expression of epithelial long noncoding RNAs (lncRNAs) and their target genes in PDAC precursor lesion formation. We focus on lncRNAs transcribed from enhancer elements near cell identity transcription factors. We demonstrate that LINC00673, expressed from a Sox9-associated super-enhancer during pancreatic development, is reactivated in PDAC. Conditional deletion of LINC00673 in the murine pancreatic epithelium accelerates resolution of ADM and significantly impairs PDAC initiation. Notably, LINC00673 harbors a variant associated with risk of developing PDAC. Our study identifies a critical function of LINC00673 in regulating both cell-autonomous and non-cell-autonomous processes during pancreas regeneration and Kras-driven cancer initiation. Furthermore, we highlight a previously unrecognized role of transcribed super-enhancers in facilitating long-range gene regulation during pancreatic cancer initiation. These findings reveal a novel regulatory layer linking developmental enhancer activity, cellular plasticity and pancreatic disease progression. TeaserLong noncoding RNAs from developmental enhancers play a role in long-range gene regulation with crucial biological impacts in development and cancer. Grant supportThis project has been supported by the Danish Cancer Society (R302-A17481). LA is supported by core funding of the Biotech Research and Innovation Center, the Danish Cancer Society (R302-A17481, R322-A17.350), The Novo Nordisk Foundation (NNF21OC0070884) and The Innovation Fund (Eurostars 2807). The Novo Nordisk Foundation Center for Stem Cell Biology was supported by Novo Nordisk Foundation grants NNF17CC0027852.

cell biology↗

bioRxiv2024

Tumor microenvironment acidosis favors pancreatic cancer stem cell properties and in vivo metastasis

The acidic tumor microenvironment favors cancer aggressiveness via incompletely understood pathways. Here, we asked whether acidic environments select for cancer stem cell (CSC) properties. Bulk RNA-seq of Panc-1 human pancreatic cancer cells adapted to extracellular pH 6.5 revealed upregulation of CSC markers including CD44, EpCam, Nestin and aldehyde dehydrogenases, and CSC pathway enrichment. We therefore assessed CSC characteristics of acid-adapted (AA) and non-adapted (Ctrl) PaTu8988s and MiaPaca-2 pancreatic cancer cells. Compared to Ctrl, AA cells exhibited increased ALDH- and {beta}-catenin activity and pancreatosphere-forming efficiency, classical CSC characteristics. Panc-1, PaTu8988s and MiaPaCa-2 AA cells differed in CSC marker expression, and AA cells did not exhibit typical flow cytometric CSC populations. However, single-nucleus sequencing identified the acid adaptation-induced emergence of a population with clear CSC characteristics. Finally, in an orthotopic mouse model, AA Panc-1 cells drove strongly increased aggressiveness and liver metastasis compared to Ctrl cells. We conclude that acid-adaptation of pancreatic cancer cells leads to enrichment of a CSC phenotype with unusual traits, providing new insight into how acidic tumor microenvironments favor cancer aggressiveness.

cancer biology↗

bioRxiv2023

Transcriptional and epigenomic profiling identifies YAP signaling as a key regulator of intestinal epithelium maturation

During intestinal organogenesis, equipotent epithelial progenitors mature into phenotypically distinct stem cells that are responsible for life-long maintenance of the tissue. While the morphological changes associated with the transition are well-characterized, the molecular mechanisms underpinning the maturation process are not fully understood. Here, we leverage intestinal organoid cultures to profile transcriptional, chromatin accessibility, DNA methylation and 3D chromatin conformation landscapes defining fetal and adult epithelial cells. We observed prominent differences in gene expression and enhancer activity, accompanied by changes in 3D organization and local changes in DNA accessibility and methylation, between the two cellular states. Using integrative analyses, we identified sustained YAP transcriptional activity as a major gatekeeper of the immature fetal state. We found the YAP-associated transcriptional network to be regulated at various levels of chromatin organization, and likely to be coordinated by changes in extracellular matrix composition. Altogether, our work highlights the value of unbiased profiling of regulatory landscapes for the identification of key mechanisms underlying tissue maturation.

developmental biology↗

bioRxiv2023

Pulmonary maternal immune activation does not extend through the placenta but leads to fetal metabolic adaptation

Maternal immune system activation (MIA) during pregnancy can disrupt the fetal environment, causing postnatal susceptibility to disorders. How the placenta and the fetus respond to acute MIA over time is unknown. Here, we characterized the response to acute maternal pulmonary inflammation across time in maternal and fetal organs using multi-omics. Unlike maternal organs which mounted strong innate immune responses, the placenta upregulated tissue-integrity genes, likely to prevent fetal exposure to infections, and downregulated growth-associated genes. Subsequently, the placenta upregulated biosynthesis and endoplasmic reticulum stress genes in order to return to homeostasis. These responses likely protected the fetus, since we observed no immune response in fetal liver. Instead, likely due to nutrient depletion, the fetal liver displayed metabolic adaptations, including increases in lipids containing docosahexaenoic acid, crucial for fetal brain development. Our study shows, for the first time, the integrated temporal response to pulmonary MIA across maternal and fetal organs.

genomics↗

bioRxiv2023

Adaptation to an acid microenvironment promotes pancreatic cancer organoid growth and drug resistance in a p53-dependent manner

The harsh environments in poorly perfused tumor regions have been proposed to select for traits that may drive cancer aggressiveness. Here, we tested the hypothesis that tumor acidosis interacts with driver mutations to exacerbate cancer hallmarks, including drug resistance, in pancreatic cancer. We gradually adapted mouse organoids from normal pancreatic duct (mN) and early PDAC (mP, with KRAS G12V mutation and +/- p53 knockout), from pH 7.4 (physiological level) to 6.7, representing acidic tumor niches. Acid adaptation rewired organoid transcriptional activity, increased viability and, strikingly, increased Gemcitabine- and Erlotinib resistance. Importantly, this response only occurred in organoids expressing wild-type p53 and was most pronounced when acid-adapted cells were returned to physiological pH (mimicking increased perfusion or invasion). While the acid adaptation transcriptional change was overall not highly similar to that induced by drug adaptation of the organoids, acid adaptation induced expression of cytidine deaminase (Cda) and ribonucleotide reductase regulatory subunit M2 (Rrm2), both associated with Gemcitabine resistance, and inhibition of these proteins partially restored Gemcitabine sensitivity. Thus, adaptation to the acidic tumor microenvironment increases drug resistance even after cells leave this niche, and this is in part dependent on acid-adaptation-induced transcriptional upregulation of Cda and Rrm2.

cancer biology↗

bioRxiv2021

PAMP-triggered Genetic Reprogramming Involves Widespread Alternative Transcription Initiation and an Immediate Transcription Factor Wave

Immune responses triggered by pathogen-associated molecular patterns (PAMPs) are key to pathogen defense, but drivers of the genetic reprogramming required to reach the immune state remain incompletely understood in plants. Here, we report a time-course study of the establishment of PAMP-triggered immunity (PTI) using cap analysis of gene expression (CAGE). Our results show that as much as 15% of all PAMP response genes display alternative transcription initiation. In several cases, use of alternative TSSs may be regulatory as it determines inclusion of target peptides or protein domains, or occurrence of upstream open reading frames (uORFs) in mRNA leader sequences. We also find that 60% of PAMP-response genes respond much earlier than previously thought. In particular, a previously unnoticed cluster of rapidly and transiently PAMP-induced genes is enriched in transcription factors whose functions, previously associated with biological processes as diverse as abiotic stress adaptation and stem cell activity, appear to converge on growth restriction. Furthermore, some examples of known potentiators of PTI, in one case under direct MAP kinase control, support the notion that the rapidly induced transcription factors could constitute direct links to PTI signaling pathways and drive gene expression changes underlying establishment of the immune state.

plant biology↗

bioRxiv2020

TrancriptomeReconstructoR: data-driven annotation of complex transcriptomes

BackgroundThe quality of gene annotation determines the interpretation of results obtained in transcriptomic studies. The growing number of genome sequence information calls for experimental and computational pipelines for de novo transcriptome annotation. Ideally, gene and transcript models should be called from a limited set of key experimental data. ResultsWe developed TranscriptomeReconstructoR, an R package which implements a pipeline for automated transcriptome annotation. It relies on integrating features from independent and complementary datasets: i) full-length RNA-seq for detection of splicing patterns and ii) high-throughput 5 and 3 tag sequencing data for accurate definition of gene borders. The pipeline can also take a nascent RNA-seq dataset to supplement the called gene model with transient transcripts. We reconstructed de novo the transcriptional landscape of wild type Arabidopsis thaliana seedlings as a proof-of-principle. A comparison to the existing transcriptome annotations revealed that our gene model is more accurate and comprehensive than the two most commonly used community gene models, TAIR10 and Araport11. In particular, we identify thousands of transient transcripts missing from the existing annotations. Our new annotation promises to improve the quality of A.thaliana genome research. ConclusionsOur proof-of-concept data suggest a cost-efficient strategy for rapid and accurate annotation of complex eukaryotic transcriptomes. We combine the choice of library preparation methods and sequencing platforms with the dedicated computational pipeline implemented in the TranscriptomeReconstructoR package. The pipeline only requires prior knowledge on the reference genomic DNA sequence, but not the transcriptome. The package seamlessly integrates with Bioconductor packages for downstream analysis.

bioinformatics↗

bioRxiv2019

Characterization of Arabidopsis thaliana promoter bidirectionality and antisense RNAs by depletion of nuclear RNA decay enzymes

In animals, transcription by RNA polymerase II initiates bidirectionally from gene promoters to produce pre-mRNAs on the forward strand and promoter upstream transcripts (PROMPTs) on the reverse strand. PROMPTs are rapidly degraded by the nuclear exosome. Similarly, active enhancer regions in animals initiate transcription of exosome-sensitive enhancer RNAs (eRNAs). Previous studies based on nascent RNA approaches concluded that Arabidopsis thaliana does not produce PROMPTs. Here, we used steady-state RNA sequencing methods in mutants defective in nuclear RNA decay, including by the exosome, to reassess the existence of PROMPTs and eRNAs in A. thaliana. While PROMPTs are overall rare in A. thaliana, about 100 clear cases of exosome-sensitive PROMPTs and 113 loci producing eRNA-like transcripts were identified. In addition, we found [~]200 transcription start sites within 3-UTR-encoding regions that produce unspliced exosome-sensitive antisense RNAs covering much of the cognate pre-mRNA. A typical representative of this class of RNAs is the previously characterized non-coding RNA controlling the expression of the key seed dormancy regulator, DELAY OF GERMINATION1. Exosome-sensitive antisense RNAs are overrepresented in transcription factor genes, suggesting a potential for widespread control of gene expression. Lastly, we assess the use of alternative promoters in A. thaliana and compare the accuracy of existing TSS annotations.

genomics↗

bioRxiv2018

IsoformSwitchAnalyzeR: Analysis of changes in genome-wide patterns of alternative splicing and its functional consequences

Alternative splicing is an important mechanism involved in both health and disease. Recent work highlights the importance of investigating genome-wide changes in patters of splicing and the subsequent functional consequences. Unfortunately current computational methods only support such analysis on a gene-by-gene basis. To fill this gap, we extended IsoformSwitchAnalyzeR thereby enabling analysis of genome-wide changes in both specific types of alternative splicing as well as the predicted functional consequences of the resulting isoform switches. As a case study, we analyzed RNA-seq data from The Cancer Genome Atlas and found systematic changes in both alternative splicing and the consequences of the associated isoform switches.\n\nAvailabilityWindows, Linux and Mac OS: http://bioconductor.org/packages/IsoformSwitchAnalyzeR.\n\nContactKVS: k.vitting.seerup@gmail.com, AS: albin@binf.ku.dk

bioinformatics↗

bioRxiv2018

CAGEfightR: Cap Analysis of Gene Expression (CAGE) in R/Bioconductor

We developed the CAGEfightR R/Biconductor-package for analyzing CAGE data. CAGEfightR allows for fast and memory efficient identification of transcription start sites (TSSs) and predicted enhancers. Downstream analysis, including annotation, quantification, visualization and TSS shape statistics are implemented in easy-to-use functions. The package is freely available at https://bioconductor.org/packages/CAGEfightR

bioinformatics↗

bioRxiv2018

Comprehensive profiling of the fission yeast transcription start site activity during stress and media response

Fission yeast, Schizosaccharomyces pombe, is an attractive model organism for transcriptional and chromatin biology research. Such research is contingent on accurate annotation of transcription start sites (TSSs). However, comprehensive genome-wide maps of TSSs and their usage across commonly applied laboratory conditions and treatments for S. pombe are lacking. To this end, we profiled TSS activity genome-wide in S. pombe cultures exposed to heat shock, nitrogen starvation, hydrogen peroxide and two commonly applied media, YES and EMM2, using Cap Analysis of Gene Expression (CAGE). CAGE-based annotation of TSSs is substantially more accurate than existing PomBase annotation; on average, CAGE TSSs fall 50-75 bp downstream of PomBase TSSs and co-localize with nucleosome boundaries. In contrast to higher eukaryotes, S. pombe does not show sharp and dispersed TSS distributions. Our data recapitulate known S. pombe stress expression response patterns and identify stress- and mediaresponsive alternative TSSs. Notably, alteration of growth medium induces changes of similar magnitude as some stressors. We show a link between nucleosome occupancy and genetic variation, and that the proximal promoter region is genetically diverse between S. pombe strains. Our detailed TSS map constitute a central resource for S. pombe gene regulation research.

genomics↗

bioRxiv2016

Shared activity patterns arising at genetic susceptibility loci reveal underlying genomic and cellular architecture of human disease.

Genetic variants underlying complex traits, including disease susceptibility, are enriched within the transcriptional regulatory elements, promoters and enhancers. There is emerging evidence that regulatory elements associated with particular traits or diseases share patterns of transcriptional regulation. Accordingly, shared transcriptional regulation (coexpression) may help prioritise loci associated with a given trait, and help to identify the biological processes underlying it. Using cap analysis of gene expression (CAGE) profiles of promoter and enhancer-derived RNAs across 1824 human samples, we have quantified coexpression of RNAs originating from trait-associated regulatory regions using a novel analytical method (network density analysis; NDA). For most traits studied, sequence variants in regulatory regions were linked to tightly coexpressed networks that are likely to share important functional characteristics. These networks implicate particular cell types and tissues in disease pathogenesis; for example, variants associated with ulcerative colitis are linked to expression in gut tissue, whereas Crohns disease variants are restricted to immune cells. We show that this coexpression signal provides additional independent information for fine mapping likely causative variants. This approach identifies additional genetic variants associated with specific traits, including an association between the regulation of the OCT1 cation transporter and genetic variants underlying circulating cholesterol levels. This approach enables a deeper biological understanding of the causal basis of complex traits.\n\nONE SENTENCE SUMMARYWe discover that variants associated with a specific disease share expression profiles across tissues and cell types, enabling fine mapping and identification of new disease-associated variants, illuminating key cell types involved in disease pathogenesis.

genomics↗