Biology subjects

Phanstiel, D. H.

Publications and source records attributed to Phanstiel, D. H..

At least 19 recordsLinked to original sources

bioRxiv2026

Mapping the response of primary human chondrocytes to an osteoarthritis-relevant stimulus by single-cell RNA sequencing

Objective: To determine how fibronectin fragment (Fn-f), a matrikine that induces an osteoarthritis (OA)-like phenotype, reshapes chondrocyte states and transcriptional programs at single-cell resolution. Design: Primary human ankle chondrocytes from two cadaveric donors without OA were treated with PBS or purified recombinant Fn-f for 18 hours and profiled by single-cell RNA sequencing. Transcriptional states were characterized by marker genes and functional enrichment, compared with classifications used for OA chondrocytes, and evaluated for Fn-f-dependent changes in abundance and transcriptional programs. Results: Five transcriptionally distinct populations were identified with features that matched previous classifications of effector, inflammatory, pre-hypertrophic/fibrochondrocyte, reparative, and homeostatic chondrocytes. Fn-f markedly redistributed cells among these states, enriching inflammatory chondrocytes while reducing effector and reparative populations. Within transcriptional states, Fn-f differentially altered matrix/cartilage, inflammatory, and stress/immediate-early programs. These responses did not uniformly correspond to assigned subtype identities, demonstrating that transcriptional programs can be dynamically deployed across chondrocyte states. Conclusions: Controlled perturbations of healthy chondrocytes complement observational OA atlases by resolving stimulus-dependent changes in chondrocyte state abundance and transcriptional programs. Discordance between subtype annotations and dynamic functional programs further highlights the need for harmonized definitions of chondrocytes across phenotypic states.

genetics↗

bioRxiv2026

CRISPR-mediated engineering of bovine satellite cells for Alpha-Gal Syndrome-compatible cultivated meat

Alpha-gal Syndrome (AGS) is a potentially life-threatening allergy caused by an IgE-mediated immune response to galactose--1,3-galactose (alpha-gal), a carbohydrate epitope present in most mammalian meats. Currently, strict avoidance of mammalian meat remains the primary management strategy for affected individuals, and alpha-gal-free beef is not commercially available. Here, we leverage cultivated meat as a biotechnology plat-form to address this unmet clinical need by engineering alpha-gal-free bovine muscle cells. Using CRISPR/Cas9 genome editing, we disrupted GGTA1, the gene encoding 1,3-galactosyltransferase, in immortalized bovine satellite cells (iBSCs). High-efficiency editing produced clonal GGTA1 knockout iBSCs harboring a homozygous frameshift mutation. Flow cytometry and immunofluorescence confirmed loss of the alpha-gal epitope, while bulk RNA-seq indicated minimal disruption of global gene expression and preserved myogenic differentiation capacity. Importantly, lysates from GGTA1 knockout iBSCs elicited substantially reduced basophil activation in assays using plasma from a patient with AGS, indicating reduced basophil activation consistent with reduced allergenic potential. Together, these findings establish a proof of concept for engineering AGS-compatible cultivated meat and demonstrate the potential of cultivated meat technologies to address human health challenges. HIGHLIGHTS{circ} CRISPR/Cas9-mediated disruption of GGTA1 eliminated alpha-gal from bovine satellite cells {circ}GGTA1 knockout cells retained myogenic identity and differentiation capacity {circ}GGTA1 knockout reduced basophil activation in an alpha-gal syndrome immune assay {circ}Genome-edited bovine cells provide a proof of concept for AGS-compatible cultivated meat

bioengineering↗

bioRxiv2025

Stress-induced loss of CTCF reveals an alternative, promoter-based mode of cohesin looping

Cells continually face environmental stressors that challenge homeostasis, yet how three-dimensional (3D) chromatin structure contributes to these stress responses remains unclear under hyperosmotic conditions. To investigate this, we map 3D chromatin structure, its molecular drivers, and transcriptional outcomes during sorbitol-induced hyperosmotic stress. Within 1 hour of sorbitol treatment, pre-existing loops and domains collapse, while several hundred de novo sorbitol-induced loops emerge. These loops are punctate, longer-range, and transient. 3D chromatin structure largely returns to baseline conditions by 24 hours. Loop reorganization is consistent across cell types and hyperosmotic stimuli. Sorbitol-induced loops require cohesin but not CTCF, and anchors are enriched at active promoters harboring GC-rich transcription factor motifs. Genes at these anchors show delayed activation following loop formation, consistent with loops acting upstream of transcription. Together, hyperosmotic stress triggers rapid, reversible, CTCF-independent chromatin reorganization that correlates with transcriptional adaptation.

genomics↗

bioRxiv2024

Response splicing QTLs in primary human chondrocytes identifies putative osteoarthritis risk genes

Osteoarthritis affects millions worldwide, yet effective treatments remain elusive due to poorly understood molecular mechanisms. While genome-wide association studies (GWAS) have identified over 100 OA-associated loci, identifying the genes impacted at each locus remains challenging. Several studies have mapped expression quantitative trait loci (eQTL) in chondrocytes and colocalized them with OA GWAS variants to identify putative OA risk genes; however, the degree to which genetic variants influence OA risk via alternative splicing has not been explored. We investigated the role of alternative splicing in OA pathogenesis using RNA-seq data from 101 human chondrocyte samples treated with PBS (control) or fibronectin fragment (FN-f), an OA trigger. We identified 590 differentially spliced genes between conditions, with FN-f inducing splicing events similar to those in primary OA tissue. We used CRISPR/Cas9 to mimic an SNRNP70 splicing event observed in OA and FN-f-treated chondrocytes and found that it induced an OA-like expression pattern. Integration with genotyping data revealed 7,188 splicing quantitative trait loci (sQTL) affecting 3,056 genes. While many sQTLs were shared, we identified 738 and 343 condition-specific sQTLs for control and FN-f, respectively. We identified 15 RNA binding proteins whose binding sites were enriched at sQTL splice junctions and found that expression of those RNA binding proteins correlated with exon inclusion. Colocalization with OA GWAS identified 6 putative risk genes, including a novel candidate, PBRM1. Our study highlights the significant impact of alternative splicing in OA and provides potential therapeutic targets for future research.

genetics↗

bioRxiv2024

Targeting the 3D genome by anthracyclines for chemotherapeutic effects

The chromatin is folded into three-dimensional (3D) structures, and aberrant 3D chromatin folding has been implicated in cancer. We performed ATAC-seq and TOP2A ChIP-seq to assess the potential effects of various anthracycline drugs on the chromatin architecture. We found that specific anthracycline variants selectively disrupt chromatin looping anchors by interfering with CTCF binding, suggesting an additional therapeutic mechanism of anthracycline drugs targeting the 3D genome. Hi-C experiments in K562 cells treated with anthracycline drugs revealed widespread disruption of 3D chromatin organization, including altered long-range regulation at the Myc locus. Furthermore, AML patients treated with anthracycline drugs exhibited changes in chromatin structures near possible looping anchors, which were associated with distinct clinical outcomes. Together, our findings indicate that anthracycline drugs function as potent and selective epigenomic modulators, with the capacity to further target the 3D genome to exert anticancer effects, highlighting their potential for personalized therapy in tumors with aberrant 3D chromatin architecture. SignificanceChromatin structure plays a crucial role in regulating gene expression and maintaining cellular function. Aberrant chromatin 3D organization is a common feature in cancer. In this study, we investigate how anthracycline chemotherapy affects chromatin architecture using state-of-the-art genomic profiling techniques, including ATAC-seq, TOP2A ChIP-seq, CTCF ChIP-seq, and Hi-C. We show that certain anthracycline variants disrupt chromatin looping by interfering with CTCF binding, thereby altering the spatial genome organization. This disruption leads to changes in the regulation of associated genes, as exemplified by the Myc locus, and is associated with distinct clinical outcomes in AML patients. These findings highlight the potential of anthracycline drugs as therapeutics that target both the epigenome and 3D chromatin architecture, a promising strategy in personalized therapy.

cancer biology↗

bioRxiv2024

Response eQTLs, chromatin accessibility, and 3D chromatin structure in chondrocytes provide mechanistic insight into osteoarthritis risk

Osteoarthritis (OA) poses a significant healthcare burden with limited treatment options. While genome-wide association studies (GWAS) have identified over 100 OA-associated loci, translating these findings into therapeutic targets remains challenging. Integrating expression quantitative trait loci (eQTL), 3D chromatin structure, and other genomic approaches with OA GWAS data offers a promising approach to elucidate disease mechanisms; however, comprehensive eQTL maps in OA-relevant tissues and conditions remain scarce. We mapped gene expression, chromatin accessibility, and 3D chromatin structure in primary human articular chondrocytes in both resting and OA-mimicking conditions. We identified thousands of differentially expressed genes, including those associated with differences in sex and age. RNA-seq in chondrocytes from 101 donors across two conditions uncovered 3782 unique eGenes, including 420 that exhibited strong and significant condition-specific effects. Colocalization with OA GWAS signals revealed 13 putative OA risk genes, 10 of which have not been previously identified. Chromatin accessibility and 3D chromatin structure provided insights into the mechanisms and conditional specificity of these variants. Our findings shed light on OA pathogenesis and highlight potential targets for therapeutic development. Highlights{circ} Comprehensive analysis of sex- and age-related global gene expression in human chondrocytes revealed differences that correlate with osteoarthritis {circ}First response eQTLs in chondrocytes treated with an OA-related stimulus {circ}Deeply sequenced Hi-C in resting and activated chondrocytes helps connect OA risk variants to their putative causal genes {circ}Colocalization analysis reveals 13 (including 10 novel) putative OA risk genes

genetics↗

bioRxiv2024

TDP-43 pathology links innate and adaptive immunity in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is the most common fatal motor neuron disease. Approximately 90% of ALS patients exhibit pathology of the master RNA regulator, Transactive Response DNA Binding protein (TDP-43). Despite the prevalence TDP-43 pathology in ALS motor neurons, recent findings suggest immune dysfunction is a determinant of disease progression in patients. Whether TDP-43 pathology elicits disease-modifying immune responses in ALS remains underexplored. In this study, we demonstrate that TDP-43 pathology is internalized by antigen presenting cells, causes vesicle rupture, and leads to innate and adaptive immune cell activation. Using a multiplex imaging platform, we observed interactions between innate and adaptive immune cells near TDP-43 pathological lesions in ALS brain. We used a mass cytometry-based whole-blood stimulation assay to provide evidence that ALS patient peripheral immune cells exhibit responses to TDP-43 aggregates. Taken together, this study provides a novel link between TDP-43 pathology and ALS immune dysfunction, and further highlights the translational and diagnostic implications of monitoring and manipulating the ALS immune response.

cell biology↗

bioRxiv2023

Guiding the design of well-powered Hi-C experiments to detect differential loops

3D chromatin structure plays an important role in gene regulation by connecting regulatory regions and gene promoters. The ability to detect the formation and loss of these loops in various cell types and conditions provides valuable information on the mechanisms driving these cell states and is critical for understanding how long-range gene regulation works. Hi-C is a powerful technique used to characterize three-dimensional chromatin structure; however, Hi-C can quickly become a costly and labor-intensive endeavor, and proper planning is required to determine how to best use time and resources while maintaining experimental rigor and well-powered results. To facilitate better planning and interpretation of Hi-C experiments, we have conducted a detailed evaluation of statistical power using publicly available Hi-C datasets paying particular attention to the impact of loop size on Hi-C contacts and fold change compression. In addition, we have developed Hi-C Poweraid, a publicly-hosted web application to investigate these findings (http://phanstiel-lab.med.unc.edu/poweraid/). For experiments involving well-replicated cell lines, we recommend a total sequencing depth of at least 6 billion contacts per condition, split between at least 2 replicates in order to achieve the power to detect the majority of differential loops. For experiments with higher variation, more replicates and deeper sequencing depths are required. Exact values and recommendations for specific cases can be determined through the use of Hi-C Poweraid. This tool simplifies the complexities behind calculating power for Hi-C data and will provide useful information on the amount of well-powered loops an experiment will be able to detect given a specific set of experimental parameters, such as sequencing depth, replicates, and the sizes of the loops of interest. This will allow for more efficient use of time and resources and more accurate interpretation of experimental results. HIGHLIGHTSO_LIDistance-dependent Hi-C contacts and fold change compression influence power C_LIO_LIIntegrative modeling of Hi-C power provides guidance for experimental design C_LIO_LIAn interactive web app aids the design of differential Hi-C experiments C_LI

bioinformatics↗

bioRxiv2022

Proximity-dependent recruitment of Polycomb Repressive Complexes by the lncRNA Airn

During mouse embryogenesis, expression of the lncRNA Airn induces gene silencing and recruits Polycomb Repressive Complexes (PRCs) to varying extents over a 15 megabase domain. The mechanisms remain unclear. Using high-resolution approaches, we show in mouse trophoblast stem cells that Airn expression induces long-range changes to chromatin architecture that coincide with PRC-directed modifications and center around CpG island promoters that contact the Airn locus even in the absence of Airn expression. Intensity of contact between Airn lncRNA and target chromatin correlated with underlying intensity of PRC-directed chromatin modifications. Deletion of CpG islands that form contacts with Airn altered long-distance silencing and PRC activity in a manner that correlated with changes in chromatin architecture. We conclude that Airn is a potent cis-acting lncRNA whose primary functions of transcriptional repression and PRC recruitment are controlled by an equilibratory network of DNA regulatory elements that modulate its frequency of contact with target chromatin.

genomics↗

bioRxiv2022

excluderanges: exclusion sets for T2T-CHM13, GRCm39, and other genome assemblies

SummaryExclusion regions are sections of reference genomes with abnormal pileups of short sequencing reads. Removing reads overlapping them improves biological signal, and these benefits are most pronounced in differential analysis settings. Several labs created exclusion region sets, available primarily through ENCODE and Github. However, the variety of exclusion sets creates uncertainty which sets to use. Furthermore, gap regions (e.g., centromeres, telomeres, short arms) create additional considerations in generating exclusion sets. We generated exclusion sets for the latest human T2T-CHM13 and mouse GRCm39 genomes and systematically assembled and annotated these and other sets in the excluderanges R/Bioconductor data package, also accessible via the BEDbase.org API. The package provides unified access to 82 GenomicRanges objects covering six organisms, multiple genome assemblies and types of exclusion regions. For human hg38 genome assembly, we recommend hg38.Kundaje.GRCh38_unified_blacklist as the most well-curated and annotated, and sets generated by the Blacklist tool for other organisms. Availability and implementationhttps://bioconductor.org/packages/excluderanges/ ContactMikhail G. Dozmorov (mdozmorov@vcu.edu) Supplementary informationPackage website: https://dozmorovlab.github.io/excluderanges/

bioinformatics↗

bioRxiv2022

Chromatin loop dynamics during cellular differentiation are associated with changes to both anchor and internal regulatory features

3D chromatin structure has been shown to play a role in regulating gene transcription during biological transitions. While our understanding of loop formation and maintenance is rapidly improving, much less is known about the mechanisms driving changes in looping and the impact of differential looping on gene transcription. One limitation has been a lack of well powered differential looping data sets. To address this, we conducted a deeply sequenced Hi-C time course of megakaryocyte development comprising 4 biological replicates and 6 billion reads per time point. Statistical analysis revealed 1,503 differential loops. Gained loops were enriched for AP-1 occupancy and correlated with increased expression of genes at their anchors. Lost loops were characterized by increases in expression of genes within the loop boundaries. Linear modeling revealed that changes in histone H3 K27 acetylation, chromatin accessibility, and JUN binding in between the loop anchors were as predictive of changes in loop strength as changes to CTCF and/or cohesin occupancy at loop anchors. Finally, we built linear models and found that incorporating the dynamics of enhancer acetylation and loop strength increased accuracy of gene expression predictions.

genomics↗

bioRxiv2022

bootRanges: Flexible generation of null sets of genomic ranges for hypothesis testing

bootRanges provides fast functions for generation of bootstrapped genomic ranges representing the null sets in enrichment analysis. We show that shuffling or permutation schemes may result in overly narrow test statistics null distributions, while creating new ranges sets with a block bootstrap preserves local genomic correlation structure and generates more reliable null distributions. It can also be used in more complex analyses, such as accessing correlations between cis-regulatory elements (CREs) and genes across cell types or providing optimized thresholds, e.g. log fold change (logFC) from differential analysis. The bootRanges functions are available in the R/Bioconductor package nullranges at https://bioconductor.org/packages/nullranges.

bioinformatics↗

bioRxiv2022

matchRanges: Generating null hypothesis genomic ranges via covariate-matched sampling

Deriving biological insights from genomic data commonly requires comparing attributes of selected genomic loci to a null set of loci. The selection of this null set is non trivial, as it requires careful consideration of potential covariates, a problem that is exacerbated by the non-uniform distribution of genomic features including genes, enhancers, and transcription factor binding sites. Propensity score-based covariate matching methods allow selection of null sets from a pool of possible items while controlling for multiple covariates; however, existing packages do not operate on genomic data classes and can be slow for large data sets making them difficult to integrate into genomic workflows. To address this, we developed matchRanges, a propensity score-based covariate matching method for the efficient and convenient generation of matched null ranges from a set of background ranges within the Bioconductor framework.

bioinformatics↗

bioRxiv2022

3D Chromatin Structure in Chondrocytes Identifies Putative Osteoarthritis Risk Genes

Genome-wide association studies (GWAS) have identified over 100 loci associated with osteoarthrtis (OA) risk, but the majority of OA risk variants are non-coding, making it difficult to identify the impacted genes for further study and therapeutic development. To address this need, we used a multi-omic approach and genome editing to identify and functionally characterize potential OA risk genes. Computational analysis of GWAS and ChIP-seq data revealed that chondrocyte regulatory loci are enriched for OA risk variants. We constructed a chondrocyte specific regulatory network by mapping 3D chromatin structure and active enhancers in human chondrocytes. We then intersected these data with our previously collected RNA-seq dataset of chondrocytes responding to fibronectin fragment (FN-f), a known OA trigger. Integration of the three genomic datasets with recently reported OA GWAS variants revealed a refined set of putative causal OA variants and their potential target genes. One of the novel putative target genes identified was SOCS2, which was connected to a putative causal variant by a 170 Kb loop and is differentially regulated in response to FN-f. CRISPR-Cas9-mediated deletion of SOCS2 in primary human chondrocytes from three independent donors led to heightened expression of inflammatory markers after FN-f treatment. These data suggest that SOCS2 plays a role in resolving inflammation in response to cartilage matrix damage and provides a possible mechanistic explanation for its influence on OA risk. In total, we identified 56 unique putative OA risk genes for further research and potential therapeutic development.

genomics↗

bioRxiv2022

Temporal analysis suggests a reciprocal relationship between 3D chromatin structure and transcription

To infer potential causal relationships between 3D chromatin structure, enhancers, and gene transcription, we mapped each feature in a genome-wide fashion across eight narrowly-spaced timepoints of macrophage activation. Enhancers and genes connected by loops exhibited stronger correlations between histone H3K27 acetylation and expression than can be explained by genomic distance or physical proximity alone. Changes in acetylation at looped distal enhancers preceded changes in gene expression. Changes in gene expression exhibit a directional bias at differential loop anchors; gained loops are associated with increased expression of genes oriented away from the center of the loop, while lost loops were often accompanied by high levels of transcription with the loop boundaries themselves. Taken together, these results are consistent with a reciprocal relationship in which loops can facilitate increased transcription by connecting promoters to distal enhancers while high levels of transcription can impede loop formation. HIGHLIGHTSO_LILPS + IFN{gamma} triggers genome-wide changes in chromatin looping, enhancer acetylation, and gene expression C_LIO_LILooped enhancer-promoter pairs exhibit ordered and correlated changes in acetylation and expression C_LIO_LIChanges in gene expression exhibit a directional bias at differential loop anchors C_LIO_LILost loops are associated with high levels of transcription within loop boundaries C_LI

genomics↗

bioRxiv2022

A multi-omic dissection of super-enhancer driven oncogenic gene expression programs in ovarian cancer

The human genome contains regulatory elements, such as enhancers, that are often rewired by cancer cells for the activation of genes that promote tumorigenesis and resistance to therapy. This is especially true for cancers that have little or no known driver mutations within protein coding genes, such as ovarian cancer. Herein, we have utilized an integrated set of genomic and epigenomic datasets to identify clinically relevant super-enhancers that are preferentially amplified in ovarian cancer patients. We have systematically probed the top 86 super-enhancers, using CRISPR-interference and CRISPR-deletion assays coupled to RNA-sequencing, to nominate two salient super-enhancers that drive proliferation and migration of cancer cells. Utilizing Hi-C, we constructed chromatin interaction maps that enabled the annotation of direct target genes for these super-enhancers and later confirmed their activity specifically within the cancer cell compartment of human tumors using single-cell genomics data. Together, our multi-omic approach has examined a number of fundamental questions about how regulatory information encoded into super-enhancers drives gene expression networks that underlie the biology of ovarian cancer.

cancer biology↗

bioRxiv2021

Fine-mapping of nuclear compartments using ultra-deep Hi-C shows that active promoter and enhancer elements localize in the active A compartment even when adjacent sequences do not

Megabase-scale intervals of active, gene-rich and inactive, gene-poor chromatin are known to segregate, forming the A and B compartments. Fine mapping of the contents of these A and B compartments has been hitherto impossible, owing to the extraordinary sequencing depths required to distinguish between the long-range contact patterns of individual loci, and to the computational complexity of the associated calculations. Here, we generate the largest published in situ Hi-C map to date, spanning 33 billion contacts. We also develop a computational method, dubbed PCA of Sparse, SUper Massive Matrices (POSSUMM), that is capable of efficiently calculating eigenvectors for sparse matrices with millions of rows and columns. Applying POSSUMM to our Hi-C dataset makes it possible to assign loci to the A and B compartment at 500 bp resolution. We find that loci frequently alternate between compartments as one moves along the contour of the genome, such that the median compartment interval is only 12.5 kb long. Contrary to the findings in coarse-resolution compartment profiles, we find that individual genes are not uniformly positioned in either the A compartment or the B compartment. Instead, essentially all (95%) active gene promoters localize in the A compartment, but the likelihood of localizing in the A compartment declines along the body of active genes, such that the transcriptional termini of long genes (>60 kb) tend to localize in the B compartment. Similarly, nearly all active enhancers elements (95%) localize in the A compartment, even when the flanking sequences are comprised entirely of inactive chromatin and localize in the B compartment. These results are consistent with a model in which DNA-bound regulatory complexes give rise to phase separation at the scale of individual DNA elements.

genomics↗

bioRxiv2021

Synthetic amyloid beta does not induce a robust transcriptional response in innate immune cell culture systems

Alzheimers disease (AD) is a progressive neurodegenerative disease that impacts nearly 400 million people worldwide. The accumulation of amyloid beta (A{beta}) in the brain has historically been associated with AD, and recent evidence suggests that neuroinflammation plays a central role in its origin and progression. These observations have given rise to the theory that A{beta} is the primary trigger of AD, and induces proinflammatory activation of immune brain cells (i.e. microglia), which culminates in neuronal damage and cognitive decline. In order to test this hypothesis, many in vitro systems have been established to study A{beta}-mediated activation of innate immune cells. Nevertheless, the transcriptional resemblance of these models to the microglia in the AD brain has never been comprehensively studied on a genome-wide scale. To address this, we used bulk RNA-seq to assess the transcriptional differences between in vitro cell types used to model neuroinflammation in AD, including several established, primary and iPSC-derived immune cell lines (macrophages, microglia and astrocytes) and their similarities to primary cells in the AD brain. We then analyzed the transcriptional response of these innate immune cells to synthetic A{beta}. We found that human induced pluripotent stem cell (hIPSC)-derived microglia (IMGL) are the in vitro cell model that best resembles primary microglia. Surprisingly, synthetic A{beta} does not trigger a robust transcriptional response in any of the cellular models analyzed, despite testing a wide variety of A{beta} formulations, concentrations, and treatment conditions. Finally, we found that bacterial LPS and INF{gamma} activate microglia and induce transcriptional changes similar to those observed in disease associated microglia present in the AD brain, suggesting the potential suitability of this model to study AD-related neuroinflammation.

neuroscience↗