Biology subjects

Blum, J.

Publications and source records attributed to Blum, J..

11 recordsLinked to original sources

bioRxiv2026

Polycomb Marked Promoter Methylation Gains in Aging and Cancer are Independent of Replication

DNA methylation alterations are hallmark features of aging and cancer, occurring early during tumor initiation. Yet how these changes evolve during early tumorigenesis, and whether oncogenic signaling actively drives them, remains poorly understood due to limitations in resolving this at the longitudinal and clonal level. Here we developed a genome-wide DNA methylation profiling method for low DNA amounts and applied it to single stem cell-derived clones from a BRAFV600E -inducible mouse colon organoid model, tracking nucleotide-level methylation heterogeneity over time. BRAFV600E induction produced stepwise methylation divergence consistent with progressive clonal takeover, in contrast to gradual epigenetic drift in uninduced controls. Strikingly, while the specific CpG sites altered differed between BRAFV600E and control lineages, they converged on the same genomic elements. Particularly, Polycomb-marked promoter CpG-island methylation gains were not induced or accelerated by BRAFV600E, challenging models in which oncogenic signaling or cell proliferation actively instructs de novo methylation of Polycomb-targeted promoters. Instead, these gains tracked with "biological aging" independent of replication, which was validated across independent aging, cancer, and cell-line datasets. BRAFV600E -induced clones additionally showed progressive loss of intestinal lineage-specification transcription factor programs, consistent with selection for cells adapted to oncogenic stress. Together, these findings show that epigenetic trajectories during early tumor development, are rooted in baseline, age-dependent drivers of epigenetic alterations, and that oncogenic signaling acts primarily by selecting and expanding clones bearing pre-existing, age-associated epigenetic drift rather than instructing new methylation. Our findings have implications for how promoter methylation is interpreted as a cancer biomarker and for identifying upstream aging-associated processes as targets for early intervention.

cancer biology↗

bioRxiv2026

Intestinal uptake regulates T cell responses to dietary antigens

Dietary proteins induce antigen-specific immune responses, leading to oral tolerance or food allergies. While mouse models of allergic sensitization rely on antigen context and adjuvant signaling, exposure to purified proteins is usually sufficient for tolerance development in studies with soluble model antigens. In previous work, we discovered that the maize protein zein induces robust antigen-specific intestinal Tregs following normal chow exposure, but unexpectedly does not elicit a T cell response when delivered as a purified protein. Here, we investigated the mechanisms underlying these differential T cell responses, considering both biochemical properties of zein and its food matrix, as well as intestinal antigen processing. We focused on three zein preparations that induced different frequencies of antigen-specific intestinal T cells. While in vitro studies showed comparable presentation by dendritic cells, in vivo studies revealed stark differences in intestinal uptake. We identified differences in protein solubility and active sampling mechanisms as cooperative drivers of intestinal zein uptake. Different zein preparations could be sampled by either goblet cells, a route previously described for the model antigen OVA, or M cells, a route hypothesized for dietary proteins and established for transport of pathogenic bacteria. These findings also extend to peanuts, where the allergen Ara h 1 was selectively transported by goblet or M cells depending on food preparation, establishing examples of naturally occurring dietary M cell ligands. Finally, solubilizing zein increased intestinal uptake, and correspondingly feeding a diet with solubilized zein led to more intestinal zein-specific T cells compared to feeding the insoluble form. Overall, these findings suggest that intestinal uptake of dietary antigens is a regulated and context-dependent determinant of antigen-specific T cell induction, with implications for development of tolerance-restoring immunotherapies.

immunology↗

bioRxiv2026

Microbiota- and diet-specific T cells become Tregs by default

CD4+ T cells recognize antigens from microbiota, diet, and pathogens via T cell receptors (TCRs) and orchestrate immunity by differentiating into tolerogenic regulatory (Treg) or pro-inflammatory effector (Teff) lineages (e.g. TH1 or TH17) (1). Dysregulation of these responses underlies numerous gastrointestinal inflammatory and infectious diseases (2-6). The prevailing paradigm suggests that individual microbes and dietary antigens drive distinct cell fates (e.g., segmented filamentous bacteria [SFB] induce TH17 cells (7) whereas Helicobacter hepaticus (8) and diet (9) induce Tregs). However, the generality of this model is uncertain: several key organisms are atypical, and foundational studies often omitted a complex microbiome or a diverse polyclonal TCR repertoire. Here we develop a high-throughput pipeline to screen hundreds of TCRs from mice colonized from birth with a 116-strain human microbiota (hCom2v), demonstrating that TCRs recognizing microbiota or dietary antigens are overwhelmingly enriched in the induced Treg (iTreg) lineage. Endogenous CD4+ T cells specific for these antigens adopt a uniform iTreg phenotype in vivo, both in hCom2v-colonized and conventional mice. This baseline tolerance is robust to acute inflammation but breaks down following a 'two-hit' combination of inflammation and genetic susceptibility, allowing Teff to emerge against otherwise Treg-restricted antigens. These data support a revised paradigm in which antigen-specific Treg induction is the default response to foreign antigens in the healthy gut, and effector responses are an exception reflecting a perceived threat. Reframing gastrointestinal immunity as a tolerance-first system provides a framework for understanding inflammatory disease pathogenesis and suggests that therapeutic strategies should aim to restore a Treg-predominant baseline.

immunology↗

bioRxiv2026

An in vivo platform to jointly monitor cellular and metabolic responses to chemotherapy.

How drug treatments reshape immune and metabolic states within intact tumors remains difficult to study with existing methods. We introduce a spatial pharmacology platform that enables parallel analysis of multiple agents within a single tumor, linking local drug exposure to immune and metabolic remodeling. Using a microdevice for localized drug delivery, we created a large-scale paired CyCIF-MALDI dataset spanning 1.5 million cells across 27 MMTV-PyMT tumor sections and nine treatment programs, enabling integrated spatial pharmacology at unprecedented scale. Metabolic signatures robustly predict proteomic spatial neighborhoods establishing metabolism as a powerful predictor of tumor organization and immune phenotype. Within this framework, we identify a dominant metabolic axis defined by the myeloid polarization between CSF1R+ tumor-associated macrophages and MPO+ infiltrating myeloid cells localized near regions of drug-induced tumor cell death. Finally, we detect putative lipid-associated macrophage (LAM)-like populations within drug-resistant treatment regions.

bioengineering↗

bioRxiv2025

Metformin inhibits mitochondrial complex I in intestinal epithelium to promote glycemic control

Metformin is a therapeutically versatile biguanide drug primarily prescribed for type II diabetes. Despite its extensive use, the mechanisms underlying many of its clinical effects, including attenuated postprandial glucose excursions, elevated intestinal glucose uptake, and increased production of lactate, Lac-Phe and GDF15, remain unclear. Here, we map these and other clinical effects of metformin to intestine-specific mitochondrial complex I inhibition. Using human metabolomic data and an orthogonal genetics approach in male mice, we demonstrate that metformin suppresses citrulline synthesis, a metabolite generated exclusively by small intestine mitochondria, and increases GDF15 by inhibiting the mitochondrial respiratory chain at complex I. This inhibition co-opts the intestines to function as a glucose sink, driving uptake of excess glucose and converting it to lactate and Lac-Phe. Notably, the glucose-lowering effect of another biguanide, phenformin, and berberine, a structurally unrelated nutraceutical, similarly depends on intestine-specific mitochondrial complex I inhibition, underscoring a shared therapeutic mechanism.

physiology↗

bioRxiv2024

Small molecule oxybutynin rescues proliferative capacity of complex III-defective MPCs

Mitochondrial disease encompasses a group of genetically inherited disorders hallmarked by an inability of the respiratory chain to produce sufficient ATP. These disorders present with multisystemic pathologies that predominantly impact highly energetic tissues such as skeletal muscle. There is no cure or effective treatment for mitochondrial disease. We have discovered a small molecule known as oxybutynin that can bypass Complex III mitochondrial dysfunction in primary murine and human skeletal muscle progenitor cells (MPCs). Oxybutynin administration improves MPC proliferative capacity, enhances cellular glycolytic function, and improves myotube formation. Mechanistically, results from our isothermal shift assay indicates that oxybutynin interacts with a suite of proteins involved in mRNA processing which then trigger the upregulation biological pathways to circumvent CIII mitochondrial dysfunction. Taken together, we provide evidence for the small molecule oxybutynin as a potential therapeutic candidate for the future treatment of CIII mitochondrial dysfunction.

cell biology↗

bioRxiv2023

Glutamine antagonist DRP-104 suppresses tumor growth and enhances response to checkpoint blockade in KEAP1 mutant lung cancer

Loss-of-function mutations in KEAP1 frequently occur in lung cancer and are associated with resistance to standard of care treatment, highlighting the need for the development of targeted therapies. We have previously shown that KEAP1 mutant tumors have increased glutamine consumption to support the metabolic rewiring associated with NRF2 activation. Here, using patient-derived xenograft models and antigenic orthotopic lung cancer models, we show that the novel glutamine antagonist DRP-104 impairs the growth of KEAP1 mutant tumors. We find that DRP-104 suppresses KEAP1 mutant tumor growth by inhibiting glutamine-dependent nucleotide synthesis and promoting anti-tumor CD4 and CD8 T cell responses. Using multimodal single-cell sequencing and ex vivo functional assays, we discover that DRP-104 reverses T cell exhaustion and enhances the function of CD4 and CD8 T cells culminating in an improved response to anti-PD1 therapy. Our pre-clinical findings provide compelling evidence that DRP-104, currently in phase 1 clinical trials, offers a promising therapeutic approach for treating patients with KEAP1 mutant lung cancer. Furthermore, we demonstrate that by combining DRP-104 with checkpoint inhibition, we can achieve suppression of tumor intrinsic metabolism and augmentation of anti-tumor T cell responses.

cancer biology↗

bioRxiv2022

Biostatistics and its impact on hazard characterization using in vitro developmental neurotoxicity assays

In the field of hazard assessment, Benchmark concentrations (BMC) and their associated uncertainty are of particular interest for regulatory decision making. The BMC estimation consists of various statistical decisions to be made, which depend largely on factors such as experimental design and assay endpoint features. In current data practice, the experimenter is often responsible for the data analysis and therefore relies on statistical software without being aware about the software default settings and how they can impact the outputs of data analysis. To provide more insight into how statistical decision making can influence the outcomes of data analysis and interpretation, we have used case studies on a large dataset produced by a developmental neurotoxicity (DNT) in vitro battery (DNT IVB). Here we focused on the BMC and its confidence interval (CI) estimation, as well as on the final hazard classification. We identified five crucial statistical decisions experimenter have to face during data analysis: choice of replicate averaging, response data normalization, regression modelling, BMC and CI estimation, as well as choice of benchmark response levels. In addition, the strength of our data evaluation platform is the integration of endpoint-specific hazard classifications, including flagging systems for uncertain cases, which none of the so far existing statistical data analysis platforms provide. The insights gained in this study demonstrate how important fit-for-purpose, internationally harmonized and accepted data evaluation and analysis procedures are for an objective hazard classification.

bioinformatics↗

bioRxiv2022

Tissue-Specific Control of Ribosomal RNA Synthesis Revealed by Transcription Factor Profiling

Ribosomal RNAs (rRNAs) are the most abundant cellular RNAs, and their synthesis from rDNA repeats by RNA Polymerase I accounts for the bulk of all transcription. Despite substantial variation in rRNA transcription rates across cell types, little is known about cell-type-specific factors that bind rDNA and regulate rRNA transcription to meet tissue-specific needs. Using hematopoiesis as a model system, we mapped about 2200 ChIP-Seq datasets for 250 transcription factors (TFs) and chromatin proteins to human and mouse rDNA, and identified robust binding of multiple TF families to canonical TF motifs on rDNA. Using a 47S-FISH-Flow assay developed for nascent rRNA quantification, we demonstrated that targeted degradation of CEBPA (C/EBP alpha), a critical hematopoietic TF with conserved rDNA binding, caused rapid reduction in rRNA transcription due to reduced Pol I occupancy. Our work identifies numerous potential rRNA regulators, and provides a template for dissection of TF roles in rRNA transcription. HIGHLIGHTSO_LIMultiple cell-type-specific transcription factors (TFs) bind canonical motifs on rDNA. C_LIO_LIThe hematopoietic TF CEBPA binds to active rDNA alleles at a conserved site. C_LIO_LICEBPA promotes Polymerase I occupancy and rRNA transcription in myeloid progenitors. C_LIO_LIWe present 47S-FISH-Flow, a sensitive assay to quantify nascent rRNA. C_LI

molecular biology↗

bioRxiv2021

Heat shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

While the RNA binding protein TDP-43 reversibly phase separates within nuclei into complex droplets (anisosomes) with TDP-43-containing liquid outer shells and liquid centers of HSP70 family chaperones, cytoplasmic aggregates of TDP-43 are hallmarks of multiple neurodegenerative diseases, including ALS. Here we show that transient oxidative stress, proteasome inhibition, or inhibition of HSP70s ATP-dependent chaperone activity provokes reversible cytoplasmic TDP-43 de-mixing and transition from liquid to gel/solid, independent of RNA binding or stress granules. Isotope labeling mass spectrometry is used to identify that phase separated cytoplasmic TDP-43 is primarily bound by the small heat shock protein HSPB1. Binding is direct, mediated through TDP-43s RNA binding and low complexity domains. HSPB1 partitions into TDP-43 droplets, inhibits TDP-43 assembly into fibrils, and is essential for disassembly of stress-induced, TDP-43 droplets. Decrease of HSPB1 promotes cytoplasmic TDP-43 de-mixing and mislocalization. HSPB1 depletion is identified within ALS-patient spinal motor neurons containing aggregated TDP-43. These findings identify HSPB1 to be a regulator of cytoplasmic TDP-43 phase separation and aggregation.

cell biology↗

bioRxiv2020

Single-cell transcriptomic analysis of the adult mouse spinal cord

The spinal cord is a fascinating structure responsible for coordinating all movement in vertebrates. Spinal motor neurons control the activity of virtually every organ and muscle throughout the body by transmitting signals that originate in the spinal cord. These neurons are remarkably heterogeneous in their activity and innervation targets. However, because motor neurons represent only a small fraction of cells within the spinal cord and are difficult to isolate, the full complement of motor neuron subtypes remains unknown. Here we comprehensively describe the molecular heterogeneity of motor neurons within the adult spinal cord. We profiled 43,890 single-nucleus transcriptomes using fluorescence-activated nuclei sorting to enrich for spinal motor neuron nuclei. These data reveal a transcriptional map of the adult mammalian spinal cord and the first unbiased characterization of all transcriptionally distinct autonomic and somatic spinal motor neuron subpopulations. We identify 16 sympathetic motor neuron subtypes that segregate spatially along the spinal cord. Many of these subtypes selectively express specific hormones and receptors, suggesting neuromodulatory signaling within the autonomic nervous system. We describe skeletal motor neuron heterogeneity in the adult spinal cord, revealing numerous novel markers that distinguish alpha and gamma motor neurons--cell populations that are specifically affected in neurodegenerative disease. We also provide evidence for a novel transcriptional subpopulation of skeletal motor neurons. Collectively, these data provide a single-cell transcriptional atlas for investigating motor neuron diversity as well as the cellular and molecular basis of motor neuron function in health and disease.

neuroscience↗